To reduce lock contention and interference with page fault handlers,
allow the TDP MMU functions which enable and disable dirty logging
to operate under the MMU read lock.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-12-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
To reduce the impact of disabling dirty logging, change the TDP MMU
function which zaps collapsible SPTEs to run under the MMU read lock.
This way, page faults on zapped SPTEs can proceed in parallel with
kvm_mmu_zap_collapsible_sptes.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-11-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
To reduce lock contention and interference with page fault handlers,
allow the TDP MMU function to zap a GFN range to operate under the MMU
read lock.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-10-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Protect the contents of the TDP MMU roots list with RCU in preparation
for a future patch which will allow the iterator macro to be used under
the MMU lock in read mode.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-9-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
To reduce dependence on the MMU write lock, don't rely on the assumption
that the atomic operation in kvm_tdp_mmu_get_root will always succeed.
By not relying on that assumption, threads do not need to hold the MMU
lock in write mode in order to take a reference on a TDP MMU root.
In the root iterator, this change means that some roots might have to be
skipped if they are found to have a zero refcount. This will still never
happen as of this patch, but a future patch will need that flexibility to
make the root iterator safe under the MMU read lock.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-8-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In order to parallelize more operations for the TDP MMU, make the
refcount on TDP MMU roots atomic, so that a future patch can allow
multiple threads to take a reference on the root concurrently, while
holding the MMU lock in read mode.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-7-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Refactor the yield safe TDP MMU root iterator to be more amenable to
changes in future commits which will allow it to be used under the MMU
lock in read mode. Currently the iterator requires a complicated dance
between the helper functions and different parts of the for loop which
makes it hard to reason about. Moving all the logic into a single function
simplifies the iterator substantially.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-6-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
kvm_tdp_mmu_put_root and kvm_tdp_mmu_free_root are always called
together, so merge the functions to simplify TDP MMU root refcounting /
freeing.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-5-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Minor cleanup to deduplicate the code used to free a struct kvm_mmu_page
in the TDP MMU.
No functional change intended.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-4-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The TDP MMU is almost the only user of kvm_mmu_get_root and
kvm_mmu_put_root. There is only one use of put_root in mmu.c for the
legacy / shadow MMU. Open code that one use and move the get / put
functions to the TDP MMU so they can be extended in future commits.
No functional change intended.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-3-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
kvm_tdp_mmu_zap_collapsible_sptes unnecessarily removes the const
qualifier from its memlsot argument, leading to a compiler warning. Add
the const annotation and pass it to subsequent functions.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-2-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Let the TDP MMU yield when unmapping a range in response to a MMU
notification, if yielding is allowed by said notification. There is no
reason to disallow yielding in this case, and in theory the range being
invalidated could be quite large.
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210402005658.3024832-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move the hva->gfn lookup for MMU notifiers into common code. Every arch
does a similar lookup, and some arch code is all but identical across
multiple architectures.
In addition to consolidating code, this will allow introducing
optimizations that will benefit all architectures without incurring
multiple walks of the memslots, e.g. by taking mmu_lock if and only if a
relevant range exists in the memslots.
The use of __always_inline to avoid indirect call retpolines, as done by
x86, may also benefit other architectures.
Consolidating the lookups also fixes a wart in x86, where the legacy MMU
and TDP MMU each do their own memslot walks.
Lastly, future enhancements to the memslot implementation, e.g. to add an
interval tree to track host address, will need to touch far less arch
specific code.
MIPS, PPC, and arm64 will be converted one at a time in future patches.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210402005658.3024832-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use a basic NOT+AND sequence to clear the Accessed bit in TDP MMU SPTEs,
as opposed to the fancy ffs()+clear_bit() logic that was copied from the
legacy MMU. The legacy MMU uses clear_bit() because it is operating on
the SPTE itself, i.e. clearing needs to be atomic. The TDP MMU operates
on a local variable that it later writes to the SPTE, and so doesn't need
to be atomic or even resident in memory.
Opportunistically drop unnecessary initialization of new_spte, it's
guaranteed to be written before being accessed.
Using NOT+AND instead of ffs()+clear_bit() reduces the sequence from:
0x0000000000058be6 <+134>: test %rax,%rax
0x0000000000058be9 <+137>: je 0x58bf4 <age_gfn_range+148>
0x0000000000058beb <+139>: test %rax,%rdi
0x0000000000058bee <+142>: je 0x58cdc <age_gfn_range+380>
0x0000000000058bf4 <+148>: mov %rdi,0x8(%rsp)
0x0000000000058bf9 <+153>: mov $0xffffffff,%edx
0x0000000000058bfe <+158>: bsf %eax,%edx
0x0000000000058c01 <+161>: movslq %edx,%rdx
0x0000000000058c04 <+164>: lock btr %rdx,0x8(%rsp)
0x0000000000058c0b <+171>: mov 0x8(%rsp),%r15
to:
0x0000000000058bdd <+125>: test %rax,%rax
0x0000000000058be0 <+128>: je 0x58beb <age_gfn_range+139>
0x0000000000058be2 <+130>: test %rax,%r8
0x0000000000058be5 <+133>: je 0x58cc0 <age_gfn_range+352>
0x0000000000058beb <+139>: not %rax
0x0000000000058bee <+142>: and %r8,%rax
0x0000000000058bf1 <+145>: mov %rax,%r15
thus eliminating several memory accesses, including a locked access.
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210331004942.2444916-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Don't clear the dirty bit when aging a TDP MMU SPTE (in response to a MMU
notifier event). Prematurely clearing the dirty bit could cause spurious
PML updates if aging a page happened to coincide with dirty logging.
Note, tdp_mmu_set_spte_no_acc_track() flows into __handle_changed_spte(),
so the host PFN will be marked dirty, i.e. there is no potential for data
corruption.
Fixes: a6a0b05da9 ("kvm: x86/mmu: Support dirty logging for the TDP MMU")
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210331004942.2444916-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Remove x86's trace_kvm_age_page() tracepoint. It's mostly redundant with
the common trace_kvm_age_hva() tracepoint, and if there is a need for the
extra details, e.g. gfn, referenced, etc... those details should be added
to the common tracepoint so that all architectures and MMUs benefit from
the info.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-19-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the leaf-only TDP iterator when changing the SPTE in reaction to a
MMU notifier. Practically speaking, this is a nop since the guts of the
loop explicitly looks for 4k SPTEs, which are always leaf SPTEs. Switch
the iterator to match age_gfn_range() and test_age_gfn() so that a future
patch can consolidate the core iterating logic.
No real functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move the address space ID check that is performed when iterating over
roots into the macro helpers to consolidate code.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Pass the address space ID to TDP MMU's primary "zap gfn range" helper to
allow the MMU notifier paths to iterate over memslots exactly once.
Currently, both the legacy MMU and TDP MMU iterate over memslots when
looking for an overlapping hva range, which can be quite costly if there
are a large number of memslots.
Add a "flush" parameter so that iterating over multiple address spaces
in the caller will continue to do the right thing when yielding while a
flush is pending from a previous address space.
Note, this also has a functional change in the form of coalescing TLB
flushes across multiple address spaces in kvm_zap_gfn_range(), and also
optimizes the TDP MMU to utilize range-based flushing when running as L1
with Hyper-V enlightenments.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-6-seanjc@google.com>
[Keep separate for loops to prepare for other incoming patches. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Gather pending TLB flushes across both the legacy and TDP MMUs when
zapping collapsible SPTEs to avoid multiple flushes if both the legacy
MMU (for nested guests) and TDP MMU have mappings for the memslot.
Note, this also optimizes the TDP MMU to flush only the relevant range
when running as L1 with Hyper-V enlightenments.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When zapping collapsible SPTEs across multiple roots, gather pending
flushes and perform a single remote TLB flush at the end, as opposed to
flushing after processing every root.
Note, flush may be cleared by the result of zap_collapsible_spte_range().
This is intended and correct, e.g. yielding may have serviced a prior
pending flush.
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Prevent the TDP MMU from yielding when zapping a gfn range during NX
page recovery. If a flush is pending from a previous invocation of the
zapping helper, either in the TDP MMU or the legacy MMU, but the TDP MMU
has not accumulated a flush for the current invocation, then yielding
will release mmu_lock with stale TLB entries.
That being said, this isn't technically a bug fix in the current code, as
the TDP MMU will never yield in this case. tdp_mmu_iter_cond_resched()
will yield if and only if it has made forward progress, as defined by the
current gfn vs. the last yielded (or starting) gfn. Because zapping a
single shadow page is guaranteed to (a) find that page and (b) step
sideways at the level of the shadow page, the TDP iter will break its loop
before getting a chance to yield.
But that is all very, very subtle, and will break at the slightest sneeze,
e.g. zapping while holding mmu_lock for read would break as the TDP MMU
wouldn't be guaranteed to see the present shadow page, and thus could step
sideways at a lower level.
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210325200119.1359384-4-seanjc@google.com>
[Add lockdep assertion. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When flushing a range of GFNs across multiple roots, ensure any pending
flush from a previous root is honored before yielding while walking the
tables of the current root.
Note, kvm_tdp_mmu_zap_gfn_range() now intentionally overwrites its local
"flush" with the result to avoid redundant flushes. zap_gfn_range()
preserves and return the incoming "flush", unless of course the flush was
performed prior to yielding and no new flush was triggered.
Fixes: 1af4a96025 ("KVM: x86/mmu: Yield in TDU MMU iter even if no SPTES changed")
Cc: stable@vger.kernel.org
Reviewed-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210325200119.1359384-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Fix ~144 single-word typos in arch/x86/ code comments.
Doing this in a single commit should reduce the churn.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-kernel@vger.kernel.org
Store the address space ID in the TDP iterator so that it can be
retrieved without having to bounce through the root shadow page. This
streamlines the code and fixes a Sparse warning about not properly using
rcu_dereference() when grabbing the ID from the root on the fly.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210315233803.2706477-5-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In tdp_mmu_iter_cond_resched there is a call to tdp_iter_start which
causes the iterator to continue its walk over the paging structure from
the root. This is needed after a yield as paging structure could have
been freed in the interim.
The tdp_iter_start call is not very clear and something of a hack. It
requires exposing tdp_iter fields not used elsewhere in tdp_mmu.c and
the effect is not obvious from the function name. Factor a more aptly
named function out of tdp_iter_start and call it from
tdp_mmu_iter_cond_resched and tdp_iter_start.
No functional change intended.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210315233803.2706477-4-bgardon@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Fix a missing rcu_dereference in tdp_mmu_zap_spte_atomic.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210315233803.2706477-3-bgardon@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The pt passed into handle_removed_tdp_mmu_page does not need RCU
protection, as it is not at any risk of being freed by another thread at
that point. However, the implicit cast from tdp_sptep_t to u64 * dropped
the __rcu annotation without a proper rcu_derefrence. Fix this by
passing the pt as a tdp_ptep_t and then rcu_dereferencing it in
the function.
Suggested-by: Sean Christopherson <seanjc@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210315233803.2706477-2-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the is_removed_spte() helper instead of open coding the check.
No functional change intended.
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-23-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Make the location of the HOST_WRITABLE and MMU_WRITABLE configurable for
a given KVM instance. This will allow EPT to use high available bits,
which in turn will free up bit 11 for a constant MMU_PRESENT bit.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-19-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Remove TDP MMU's call to trace_kvm_mmu_set_spte() that is done for both
shadow-present SPTEs and MMIO SPTEs. It's fully redundant for the
former, and unnecessary for the latter. This aligns TDP MMU tracing
behavior with that of the legacy MMU.
Fixes: 33dd3574f5 ("kvm: x86/mmu: Add existing trace points to TDP MMU")
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-9-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When updating accessed and dirty bits, check that the new SPTE is present
before attempting to query its A/D bits. Failure to confirm the SPTE is
present can theoretically cause a false negative, e.g. if a MMIO SPTE
replaces a "real" SPTE and somehow the PFNs magically match.
Realistically, this is all but guaranteed to be a benign bug. Fix it up
primarily so that a future patch can tweak the MMU_WARN_ON checking A/D
status to fire if the SPTE is not-present.
Fixes: f8e144971c ("kvm: x86/mmu: Add access tracking for tdp_mmu")
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a TDP MMU helper to handle a single HVA hook, the name is a nice
reminder that the flow in question is operating on a single HVA.
No functional change intended.
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210226010329.1766033-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add typedefs for the MMU handlers that are invoked when walking the MMU
SPTEs (rmaps in legacy MMU) to act on a host virtual address range.
No functional change intended.
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210226010329.1766033-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the @end param when aging a GFN instead of hardcoding the walk to a
single GFN. Unlike tdp_set_spte(), which simply cannot work with more
than one GFN, aging multiple GFNs would not break, though admittedly it
would be weird. Be nice to the casual reader and don't make them puzzle
out why the end GFN is unused.
No functional change intended.
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210226010329.1766033-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
WARN if set_tdp_spte() is invoked with multipel GFNs. It is specifically
a callback to handle a single host PTE being changed. Consuming the
@end parameter also eliminates the confusing 'unused' parameter.
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210226010329.1766033-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Remove an unnecessary remote TLB flush from set_tdp_spte(), the TDP MMu's
hook for handling change_pte() invocations from the MMU notifier. If
the new host PTE is writable, the flush is completely redundant as there
are no futher changes to the SPTE before the post-loop flush. If the
host PTE is read-only, then the primary MMU is responsible for ensuring
that the contents of the old and new pages are identical, thus it's safe
to let the guest continue reading both the old and new pages. KVM must
only ensure the old page cannot be referenced after returning from its
callback; this is handled by the post-loop flush.
Fixes: 1d8dd6b3f1 ("kvm: x86/mmu: Support changed pte notifier in tdp MMU")
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210226010329.1766033-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Hold the mmu_lock for write for the entire duration of allocating and
initializing an MMU's roots. This ensures there are MMU pages available
and thus prevents root allocations from failing. That in turn fixes a
bug where KVM would fail to free valid PAE roots if a one of the later
roots failed to allocate.
Add a comment to make_mmu_pages_available() to call out that the limit
is a soft limit, e.g. KVM will temporarily exceed the threshold if a
page fault allocates multiple shadow pages and there was only one page
"available".
Note, KVM _still_ leaks the PAE roots if the guest PDPTR checks fail.
This will be addressed in a future commit.
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
If mmu_lock is held for write, don't bother setting !PRESENT SPTEs to
REMOVED_SPTE when recursively zapping SPTEs as part of shadow page
removal. The concurrent write protections provided by REMOVED_SPTE are
not needed, there are no backing page side effects to record, and MMIO
SPTEs can be left as is since they are protected by the memslot
generation, not by ensuring that the MMIO SPTE is unreachable (which
is racy with respect to lockless walks regardless of zapping behavior).
Skipping !PRESENT drastically reduces the number of updates needed to
tear down sparsely populated MMUs, e.g. when tearing down a 6gb VM that
didn't touch much memory, 6929/7168 (~96.6%) of SPTEs were '0' and could
be skipped.
Avoiding the write itself is likely close to a wash, but avoiding
__handle_changed_spte() is a clear-cut win as that involves saving and
restoring all non-volatile GPRs (it's a subtly big function), as well as
several conditional branches before bailing out.
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210310003029.1250571-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Stop setting dirty bits for MMU pages when dirty logging is disabled for
a memslot, as PML is now completely disabled when there are no memslots
with dirty logging enabled.
This means that spurious PML entries will be created for memslots with
dirty logging disabled if at least one other memslot has dirty logging
enabled. However, spurious PML entries are already possible since
dirty bits are set only when a dirty logging is turned off, i.e. memslots
that are never dirty logged will have dirty bits cleared.
In the end, it's faster overall to eat a few spurious PML entries in the
window where dirty logging is being disabled across all memslots.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210213005015.1651772-13-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When zapping SPTEs in order to rebuild them as huge pages, use the new
helper that computes the max mapping level to detect whether or not a
SPTE should be zapped. Doing so avoids zapping SPTEs that can't
possibly be rebuilt as huge pages, e.g. due to hardware constraints,
memslot alignment, etc...
This also avoids zapping SPTEs that are still large, e.g. if migration
was canceled before write-protected huge pages were shattered to enable
dirty logging. Note, such pages are still write-protected at this time,
i.e. a page fault VM-Exit will still occur. This will hopefully be
addressed in a future patch.
Sadly, TDP MMU loses its const on the memslot, but that's a pervasive
problem that's been around for quite some time.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210213005015.1651772-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Zap SPTEs that are backed by ZONE_DEVICE pages when zappings SPTEs to
rebuild them as huge pages in the TDP MMU. ZONE_DEVICE huge pages are
managed differently than "regular" pages and are not compound pages.
Likewise, PageTransCompoundMap() will not detect HugeTLB, so switch
to PageCompound().
This matches the similar check in kvm_mmu_zap_collapsible_spte.
Cc: Ben Gardon <bgardon@google.com>
Fixes: 1488199856 ("kvm: x86/mmu: Support disabling dirty logging for the tdp MMU")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210213005015.1651772-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When retpolines are enabled they have high overhead in the inner loop
inside kvm_handle_hva_range() that iterates over the provided memory area.
Let's mark this function and its TDP MMU equivalent __always_inline so
compiler will be able to change the call to the actual handler function
inside each of them into a direct one.
This significantly improves performance on the unmap test on the existing
kernel memslot code (tested on a Xeon 8167M machine):
30 slots in use:
Test Before After Improvement
Unmap 0.0353s 0.0334s 5%
Unmap 2M 0.00104s 0.000407s 61%
509 slots in use:
Test Before After Improvement
Unmap 0.0742s 0.0740s None
Unmap 2M 0.00221s 0.00159s 28%
Looks like having an indirect call in these functions (and, so, a
retpoline) might have interfered with unrolling of the whole loop in the
CPU.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Message-Id: <732d3fe9eb68aa08402a638ab0309199fa89ae56.1612810129.git.maciej.szmigiero@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The TDP MMU assumes that it can do atomic accesses to 64-bit PTEs.
Rather than just disabling it, compile it out completely so that it
is possible to use for example 64-bit xchg.
To limit the number of stubs, wrap all accesses to tdp_mmu_enabled
or tdp_mmu_page with a function. Calls to all other functions in
tdp_mmu.c are eliminated and do not even reach the linker.
Reviewed-by: Sean Christopherson <seanjc@google.com>
Tested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When clearing TDP MMU pages what have been disconnected from the paging
structure root, set the SPTEs to a special non-present value which will
not be overwritten by other threads. This is needed to prevent races in
which a thread is clearing a disconnected page table, but another thread
has already acquired a pointer to that memory and installs a mapping in
an already cleared entry. This can lead to memory leaks and accounting
errors.
Reviewed-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-23-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When the TDP MMU is allowed to handle page faults in parallel there is
the possiblity of a race where an SPTE is cleared and then imediately
replaced with a present SPTE pointing to a different PFN, before the
TLBs can be flushed. This race would violate architectural specs. Ensure
that the TLBs are flushed properly before other threads are allowed to
install any present value for the SPTE.
Reviewed-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-22-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
To prepare for handling page faults in parallel, change the TDP MMU
page fault handler to use atomic operations to set SPTEs so that changes
are not lost if multiple threads attempt to modify the same SPTE.
Reviewed-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-21-bgardon@google.com>
[Document new locking rules. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move the work of adding and removing TDP MMU pages to/from "secondary"
data structures to helper functions. These functions will be built on in
future commits to enable MMU operations to proceed (mostly) in parallel.
No functional change expected.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-20-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a read / write lock to be used in place of the MMU spinlock on x86.
The rwlock will enable the TDP MMU to handle page faults, and other
operations in parallel in future commits.
Reviewed-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-19-bgardon@google.com>
[Introduce virt/kvm/mmu_lock.h - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In order to enable concurrent modifications to the paging structures in
the TDP MMU, threads must be able to safely remove pages of page table
memory while other threads are traversing the same memory. To ensure
threads do not access PT memory after it is freed, protect PT memory
with RCU.
Protecting concurrent accesses to page table memory from use-after-free
bugs could also have been acomplished using
walk_shadow_page_lockless_begin/end() and READING_SHADOW_PAGE_TABLES,
coupling with the barriers in a TLB flush. The use of RCU for this case
has several distinct advantages over that approach.
1. Disabling interrupts for long running operations is not desirable.
Future commits will allow operations besides page faults to operate
without the exclusive protection of the MMU lock and those operations
are too long to disable iterrupts for their duration.
2. The use of RCU here avoids long blocking / spinning operations in
perfromance critical paths. By freeing memory with an asynchronous
RCU API we avoid the longer wait times TLB flushes experience when
overlapping with a thread in walk_shadow_page_lockless_begin/end().
3. RCU provides a separation of concerns when removing memory from the
paging structure. Because the RCU callback to free memory can be
scheduled immediately after a TLB flush, there's no need for the
thread to manually free a queue of pages later, as commit_zap_pages
does.
Fixes: 95fb5b0258 ("kvm: x86/mmu: Support MMIO in the TDP MMU")
Reviewed-by: Peter Feiner <pfeiner@google.com>
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-18-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In clear_dirty_pt_masked, the loop is intended to exit early after
processing each of the GFNs with corresponding bits set in mask. This
does not work as intended if another thread has already cleared the
dirty bit or writable bit on the SPTE. In that case, the loop would
proceed to the next iteration early and the bit in mask would not be
cleared. As a result the loop could not exit early and would proceed
uselessly. Move the unsetting of the mask bit before the check for a
no-op SPTE change.
Fixes: a6a0b05da9 ("kvm: x86/mmu: Support dirty logging for the TDP
MMU")
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-17-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Skip setting SPTEs if no change is expected.
Reviewed-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-16-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Given certain conditions, some TDP MMU functions may not yield
reliably / frequently enough. For example, if a paging structure was
very large but had few, if any writable entries, wrprot_gfn_range
could traverse many entries before finding a writable entry and yielding
because the check for yielding only happens after an SPTE is modified.
Fix this issue by moving the yield to the beginning of the loop.
Fixes: a6a0b05da9 ("kvm: x86/mmu: Support dirty logging for the TDP MMU")
Reviewed-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-15-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In some functions the TDP iter risks not making forward progress if two
threads livelock yielding to one another. This is possible if two threads
are trying to execute wrprot_gfn_range. Each could write protect an entry
and then yield. This would reset the tdp_iter's walk over the paging
structure and the loop would end up repeating the same entry over and
over, preventing either thread from making forward progress.
Fix this issue by only yielding if the loop has made forward progress
since the last yield.
Fixes: a6a0b05da9 ("kvm: x86/mmu: Support dirty logging for the TDP MMU")
Reviewed-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-14-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The flushing and non-flushing variants of tdp_mmu_iter_cond_resched have
almost identical implementations. Merge the two functions and add a
flush parameter.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-12-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Factor out the code to handle a disconnected subtree of the TDP paging
structure from the code to handle the change to an individual SPTE.
Future commits will build on this to allow asynchronous page freeing.
No functional change intended.
Reviewed-by: Peter Feiner <pfeiner@google.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-6-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The KVM MMU caches already guarantee that shadow page table memory will
be zeroed, so there is no reason to re-zero the page in the TDP MMU page
fault handler.
No functional change intended.
Reviewed-by: Peter Feiner <pfeiner@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-5-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add lockdep to __tdp_mmu_set_spte to ensure that SPTEs are only modified
under the MMU lock.
No functional change intended.
Reviewed-by: Peter Feiner <pfeiner@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-4-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
__tdp_mmu_set_spte is a very important function in the TDP MMU which
already accepts several arguments and will take more in future commits.
To offset this complexity, add a comment to the function describing each
of the arguemnts.
No functional change intended.
Reviewed-by: Peter Feiner <pfeiner@google.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-3-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Currently the TDP MMU yield / cond_resched functions either return
nothing or return true if the TLBs were not flushed. These are confusing
semantics, especially when making control flow decisions in calling
functions.
To clean things up, change both functions to have the same
return value semantics as cond_resched: true if the thread yielded,
false if it did not. If the function yielded in the _flush_ version,
then the TLBs will have been flushed.
Reviewed-by: Peter Feiner <pfeiner@google.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-2-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
There is a bug in the TDP MMU function to zap SPTEs which could be
replaced with a larger mapping which prevents the function from doing
anything. Fix this by correctly zapping the last level SPTEs.
Cc: stable@vger.kernel.org
Fixes: 1488199856 ("kvm: x86/mmu: Support disabling dirty logging for the tdp MMU")
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-11-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Many TDP MMU functions which need to perform some action on all TDP MMU
roots hold a reference on that root so that they can safely drop the MMU
lock in order to yield to other threads. However, when releasing the
reference on the root, there is a bug: the root will not be freed even
if its reference count (root_count) is reduced to 0.
To simplify acquiring and releasing references on TDP MMU root pages, and
to ensure that these roots are properly freed, move the get/put operations
into another TDP MMU root iterator macro.
Moving the get/put operations into an iterator macro also helps
simplify control flow when a root does need to be freed. Note that using
the list_for_each_entry_safe macro would not have been appropriate in
this situation because it could keep a pointer to the next root across
an MMU lock release + reacquire, during which time that root could be
freed.
Reported-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Fixes: faaf05b00a ("kvm: x86/mmu: Support zapping SPTEs in the TDP MMU")
Fixes: 063afacd87 ("kvm: x86/mmu: Support invalidate range MMU notifier for TDP MMU")
Fixes: a6a0b05da9 ("kvm: x86/mmu: Support dirty logging for the TDP MMU")
Fixes: 1488199856 ("kvm: x86/mmu: Support disabling dirty logging for the tdp MMU")
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210107001935.3732070-1-bgardon@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Bump the size of the sptes array by one and use the raw level of the
SPTE to index into the sptes array. Using the SPTE level directly
improves readability by eliminating the need to reason out why the level
is being adjusted when indexing the array. The array is on the stack
and is not explicitly initialized; bumping its size is nothing more than
a superficial adjustment to the stack frame.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20201218003139.2167891-4-seanjc@google.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Get the so called "root" level from the low level shadow page table
walkers instead of manually attempting to calculate it higher up the
stack, e.g. in get_mmio_spte(). When KVM is using PAE shadow paging,
the starting level of the walk, from the callers perspective, is not
the CR3 root but rather the PDPTR "root". Checking for reserved bits
from the CR3 root causes get_mmio_spte() to consume uninitialized stack
data due to indexing into sptes[] for a level that was not filled by
get_walk(). This can result in false positives and/or negatives
depending on what garbage happens to be on the stack.
Opportunistically nuke a few extra newlines.
Fixes: 95fb5b0258 ("kvm: x86/mmu: Support MMIO in the TDP MMU")
Reported-by: Richard Herbert <rherbert@sympatico.ca>
Cc: Ben Gardon <bgardon@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20201218003139.2167891-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Return -1 from the get_walk() helpers if the shadow walk doesn't fill at
least one spte, which can theoretically happen if the walk hits a
not-present PDPTR. Returning the root level in such a case will cause
get_mmio_spte() to return garbage (uninitialized stack data). In
practice, such a scenario should be impossible as KVM shouldn't get a
reserved-bit page fault with a not-present PDPTR.
Note, using mmu->root_level in get_walk() is wrong for other reasons,
too, but that's now a moot point.
Fixes: 95fb5b0258 ("kvm: x86/mmu: Support MMIO in the TDP MMU")
Cc: Ben Gardon <bgardon@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20201218003139.2167891-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In the TDP MMU, use shadow_phys_bits to dermine the maximum possible GFN
mapped in the guest for zapping operations. boot_cpu_data.x86_phys_bits
may be reduced in the case of HW features that steal HPA bits for other
purposes. However, this doesn't necessarily reduce GPA space that can be
accessed via TDP. So zap based on a maximum gfn calculated with MAXPHYADDR
retrieved from CPUID. This is already stored in shadow_phys_bits, so use
it instead of x86_phys_bits.
Fixes: faaf05b00a ("kvm: x86/mmu: Support zapping SPTEs in the TDP MMU")
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Message-Id: <20201203231120.27307-1-rick.p.edgecombe@intel.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add an extremely verbose trace point to the TDP MMU to log all SPTE
changes, regardless of callstack / motivation. This is useful when a
complete picture of the paging structure is needed or a change cannot be
explained with the other, existing trace points.
Tested: ran the demand paging selftest on an Intel Skylake machine with
all the trace points used by the TDP MMU enabled and observed
them firing with expected values.
This patch can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/3813
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201027175944.1183301-2-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The TDP MMU was initially implemented without some of the usual
tracepoints found in mmu.c. Correct this discrepancy by adding the
missing trace points to the TDP MMU.
Tested: ran the demand paging selftest on an Intel Skylake machine with
all the trace points used by the TDP MMU enabled and observed
them firing with expected values.
This patch can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/3812
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201027175944.1183301-1-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This patch is heavily based on previous work from Lei Cao
<lei.cao@stratus.com> and Paolo Bonzini <pbonzini@redhat.com>. [1]
KVM currently uses large bitmaps to track dirty memory. These bitmaps
are copied to userspace when userspace queries KVM for its dirty page
information. The use of bitmaps is mostly sufficient for live
migration, as large parts of memory are be dirtied from one log-dirty
pass to another. However, in a checkpointing system, the number of
dirty pages is small and in fact it is often bounded---the VM is
paused when it has dirtied a pre-defined number of pages. Traversing a
large, sparsely populated bitmap to find set bits is time-consuming,
as is copying the bitmap to user-space.
A similar issue will be there for live migration when the guest memory
is huge while the page dirty procedure is trivial. In that case for
each dirty sync we need to pull the whole dirty bitmap to userspace
and analyse every bit even if it's mostly zeros.
The preferred data structure for above scenarios is a dense list of
guest frame numbers (GFN). This patch series stores the dirty list in
kernel memory that can be memory mapped into userspace to allow speedy
harvesting.
This patch enables dirty ring for X86 only. However it should be
easily extended to other archs as well.
[1] https://patchwork.kernel.org/patch/10471409/
Signed-off-by: Lei Cao <lei.cao@stratus.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20201001012222.5767-1-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In some cases where shadow paging is in use, the root page will
be either mmu->pae_root or vcpu->arch.mmu->lm_root. Then it will
not have an associated struct kvm_mmu_page, because it is allocated
with alloc_page instead of kvm_mmu_alloc_page.
Just return false quickly from is_tdp_mmu_root if the TDP MMU is
not in use, which also includes the case where shadow paging is
enabled.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Replace a modulo operator with the more common pattern for computing the
gfn "offset" of a huge page to fix an i386 build error.
arch/x86/kvm/mmu/tdp_mmu.c:212: undefined reference to `__umoddi3'
In fact, almost all of tdp_mmu.c can be elided on 32-bit builds, but
that is a much larger patch.
Fixes: 2f2fad0897 ("kvm: x86/mmu: Add functions to handle changed TDP SPTEs")
Reported-by: Daniel Díaz <daniel.diaz@linaro.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20201024031150.9318-1-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When KVM maps a largepage backed region at a lower level in order to
make it executable (i.e. NX large page shattering), it reduces the TLB
performance of that region. In order to avoid making this degradation
permanent, KVM must periodically reclaim shattered NX largepages by
zapping them and allowing them to be rebuilt in the page fault handler.
With this patch, the TDP MMU does not respect KVM's rate limiting on
reclaim. It traverses the entire TDP structure every time. This will be
addressed in a future patch.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-21-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In order to support MMIO, KVM must be able to walk the TDP paging
structures to find mappings for a given GFN. Support this walk for
the TDP MMU.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
v2: Thanks to Dan Carpenter and kernel test robot for finding that root
was used uninitialized in get_mmio_spte.
Signed-off-by: Ben Gardon <bgardon@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Message-Id: <20201014182700.2888246-19-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
To support nested virtualization, KVM will sometimes need to write
protect pages which are part of a shadowed paging structure or are not
writable in the shadowed paging structure. Add a function to write
protect GFN mappings for this purpose.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-18-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Dirty logging ultimately breaks down MMU mappings to 4k granularity.
When dirty logging is no longer needed, these granaular mappings
represent a useless performance penalty. When dirty logging is disabled,
search the paging structure for mappings that could be re-constituted
into a large page mapping. Zap those mappings so that they can be
faulted in again at a higher mapping level.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-17-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Dirty logging is a key feature of the KVM MMU and must be supported by
the TDP MMU. Add support for both the write protection and PML dirty
logging modes.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-16-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In order to interoperate correctly with the rest of KVM and other Linux
subsystems, the TDP MMU must correctly handle various MMU notifiers. Add
a hook and handle the change_pte MMU notifier.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-15-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In order to interoperate correctly with the rest of KVM and other Linux
subsystems, the TDP MMU must correctly handle various MMU notifiers. The
main Linux MM uses the access tracking MMU notifiers for swap and other
features. Add hooks to handle the test/flush HVA (range) family of
MMU notifiers.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-14-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In order to interoperate correctly with the rest of KVM and other Linux
subsystems, the TDP MMU must correctly handle various MMU notifiers. Add
hooks to handle the invalidate range family of MMU notifiers.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-13-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Attach struct kvm_mmu_pages to every page in the TDP MMU to track
metadata, facilitate NX reclaim, and enable inproved parallelism of MMU
operations in future patches.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-12-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add functions to handle page faults in the TDP MMU. These page faults
are currently handled in much the same way as the x86 shadow paging
based MMU, however the ordering of some operations is slightly
different. Future patches will add eager NX splitting, a fast page fault
handler, and parallel page faults.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-11-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add functions to zap SPTEs to the TDP MMU. These are needed to tear down
TDP MMU roots properly and implement other MMU functions which require
tearing down mappings. Future patches will add functions to populate the
page tables, but as for this patch there will not be any work for these
functions to do.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-8-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The existing bookkeeping done by KVM when a PTE is changed is spread
around several functions. This makes it difficult to remember all the
stats, bitmaps, and other subsystems that need to be updated whenever a
PTE is modified. When a non-leaf PTE is marked non-present or becomes a
leaf PTE, page table memory must also be freed. To simplify the MMU and
facilitate the use of atomic operations on SPTEs in future patches, create
functions to handle some of the bookkeeping required as a result of
a change.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The TDP MMU must be able to allocate paging structure root pages and track
the usage of those pages. Implement a similar, but separate system for root
page allocation to that of the x86 shadow paging implementation. When
future patches add synchronization model changes to allow for parallel
page faults, these pages will need to be handled differently from the
x86 shadow paging based MMU's root pages.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The TDP MMU offers an alternative mode of operation to the x86 shadow
paging based MMU, optimized for running an L1 guest with TDP. The TDP MMU
will require new fields that need to be initialized and torn down. Add
hooks into the existing KVM MMU initialization process to do that
initialization / cleanup. Currently the initialization and cleanup
fucntions do not do very much, however more operations will be added in
future patches.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-4-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
