Neither tdp_mmu_next_root nor kvm_tdp_mmu_put_root need to know
if the lock is taken for read or write. Either way, protection
is achieved via RCU and tdp_mmu_pages_lock. Remove the argument
and just assert that the lock is taken.
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20231125083400.1399197-2-pbonzini@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Stop zapping invalidate TDP MMU roots via work queue now that KVM
preserves TDP MMU roots until they are explicitly invalidated. Zapping
roots asynchronously was effectively a workaround to avoid stalling a vCPU
for an extended during if a vCPU unloaded a root, which at the time
happened whenever the guest toggled CR0.WP (a frequent operation for some
guest kernels).
While a clever hack, zapping roots via an unbound worker had subtle,
unintended consequences on host scheduling, especially when zapping
multiple roots, e.g. as part of a memslot. Because the work of zapping a
root is no longer bound to the task that initiated the zap, things like
the CPU affinity and priority of the original task get lost. Losing the
affinity and priority can be especially problematic if unbound workqueues
aren't affined to a small number of CPUs, as zapping multiple roots can
cause KVM to heavily utilize the majority of CPUs in the system, *beyond*
the CPUs KVM is already using to run vCPUs.
When deleting a memslot via KVM_SET_USER_MEMORY_REGION, the async root
zap can result in KVM occupying all logical CPUs for ~8ms, and result in
high priority tasks not being scheduled in in a timely manner. In v5.15,
which doesn't preserve unloaded roots, the issues were even more noticeable
as KVM would zap roots more frequently and could occupy all CPUs for 50ms+.
Consuming all CPUs for an extended duration can lead to significant jitter
throughout the system, e.g. on ChromeOS with virtio-gpu, deleting memslots
is a semi-frequent operation as memslots are deleted and recreated with
different host virtual addresses to react to host GPU drivers allocating
and freeing GPU blobs. On ChromeOS, the jitter manifests as audio blips
during games due to the audio server's tasks not getting scheduled in
promptly, despite the tasks having a high realtime priority.
Deleting memslots isn't exactly a fast path and should be avoided when
possible, and ChromeOS is working towards utilizing MAP_FIXED to avoid the
memslot shenanigans, but KVM is squarely in the wrong. Not to mention
that removing the async zapping eliminates a non-trivial amount of
complexity.
Note, one of the subtle behaviors hidden behind the async zapping is that
KVM would zap invalidated roots only once (ignoring partial zaps from
things like mmu_notifier events). Preserve this behavior by adding a flag
to identify roots that are scheduled to be zapped versus roots that have
already been zapped but not yet freed.
Add a comment calling out why kvm_tdp_mmu_invalidate_all_roots() can
encounter invalid roots, as it's not at all obvious why zapping
invalidated roots shouldn't simply zap all invalid roots.
Reported-by: Pattara Teerapong <pteerapong@google.com>
Cc: David Stevens <stevensd@google.com>
Cc: Yiwei Zhang<zzyiwei@google.com>
Cc: Paul Hsia <paulhsia@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230916003916.2545000-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
All callers except the MMU notifier want to process all address spaces.
Remove the address space ID argument of for_each_tdp_mmu_root_yield_safe()
and switch the MMU notifier to use __for_each_tdp_mmu_root_yield_safe().
Extracted out of a patch by Sean Christopherson <seanjc@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The mmu_notifier path is a bit of a special snowflake, e.g. it zaps only a
single address space (because it's per-slot), and can't always yield.
Because of this, it calls kvm_tdp_mmu_zap_leafs() in ways that no one
else does.
Iterate manually over the leafs in response to an mmu_notifier
invalidation, instead of invoking kvm_tdp_mmu_zap_leafs(). Drop the
@can_yield param from kvm_tdp_mmu_zap_leafs() as its sole remaining
caller unconditionally passes "true".
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230916003916.2545000-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Simplify and optimize the logic for detecting if the current/active MMU
is a TDP MMU. If the TDP MMU is globally enabled, then the active MMU is
a TDP MMU if it is direct. When TDP is enabled, so called nonpaging MMUs
are never used as the only form of shadow paging KVM uses is for nested
TDP, and the active MMU can't be direct in that case.
Rename the helper and take the vCPU instead of an arbitrary MMU, as
nonpaging MMUs can show up in the walk_mmu if L1 is using nested TDP and
L2 has paging disabled. Taking the vCPU has the added bonus of cleaning
up the callers, all of which check the current MMU but wrap code that
consumes the vCPU.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20221012181702.3663607-9-seanjc@google.com>
[Use tdp_mmu_enabled variable. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move kvm_mmu_{init,uninit}_tdp_mmu() behind tdp_mmu_enabled. This makes
these functions consistent with the rest of the calls into the TDP MMU
from mmu.c, and which is now possible since tdp_mmu_enabled is only
modified when the x86 vendor module is loaded. i.e. It will never change
during the lifetime of a VM.
This change also enabled removing the stub definitions for 32-bit KVM,
as the compiler will just optimize the calls out like it does for all
the other TDP MMU functions.
No functional change intended.
Signed-off-by: David Matlack <dmatlack@google.com>
Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220921173546.2674386-3-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a helper to convert a SPTE to its shadow page to deduplicate a
variety of flows and hopefully avoid future bugs, e.g. if KVM attempts to
get the shadow page for a SPTE without dropping high bits.
Opportunistically add a comment in mmu_free_root_page() documenting why
it treats the root HPA as a SPTE.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20221019165618.927057-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Re-introduce zapping only leaf SPTEs in kvm_zap_gfn_range() and
kvm_tdp_mmu_unmap_gfn_range(), this time without losing a pending TLB
flush when processing multiple roots (including nested TDP shadow roots).
Dropping the TLB flush resulted in random crashes when running Hyper-V
Server 2019 in a guest with KSM enabled in the host (or any source of
mmu_notifier invalidations, KSM is just the easiest to force).
This effectively revert commits 873dd12217
and fcb93eb6d0, and thus restores commit
cf3e26427c, plus this delta on top:
bool kvm_tdp_mmu_zap_leafs(struct kvm *kvm, int as_id, gfn_t start, gfn_t end,
struct kvm_mmu_page *root;
for_each_tdp_mmu_root_yield_safe(kvm, root, as_id)
- flush = tdp_mmu_zap_leafs(kvm, root, start, end, can_yield, false);
+ flush = tdp_mmu_zap_leafs(kvm, root, start, end, can_yield, flush);
return flush;
}
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20220325230348.2587437-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
If kvm->arch.tdp_mmu_zap_wq cannot be created, the failure has
to be propagated up to kvm_mmu_init_vm and kvm_arch_init_vm.
kvm_arch_init_vm also has to undo all the initialization, so
group all the MMU initialization code at the beginning and
handle cleaning up of kvm_page_track_init.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This reverts commit cf3e26427c.
Multi-vCPU Hyper-V guests started crashing randomly on boot with the
latest kvm/queue and the problem can be bisected the problem to this
particular patch. Basically, I'm not able to boot e.g. 16-vCPU guest
successfully anymore. Both Intel and AMD seem to be affected. Reverting
the commit saves the day.
Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Zap only leaf SPTEs in the TDP MMU's zap_gfn_range(), and rename various
functions accordingly. When removing mappings for functional correctness
(except for the stupid VFIO GPU passthrough memslots bug), zapping the
leaf SPTEs is sufficient as the paging structures themselves do not point
at guest memory and do not directly impact the final translation (in the
TDP MMU).
Note, this aligns the TDP MMU with the legacy/full MMU, which zaps only
the rmaps, a.k.a. leaf SPTEs, in kvm_zap_gfn_range() and
kvm_unmap_gfn_range().
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Ben Gardon <bgardon@google.com>
Message-Id: <20220226001546.360188-18-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When recovering a potential hugepage that was shattered for the iTLB
multihit workaround, precisely zap only the target page instead of
iterating over the TDP MMU to find the SP that was passed in. This will
allow future simplification of zap_gfn_range() by having it zap only
leaf SPTEs.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220226001546.360188-14-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The root_hpa and root_pgd fields form essentially a struct kvm_mmu_root_info.
Use the struct to have more consistency between mmu->root and
mmu->prev_roots.
The patch is entirely search and replace except for cached_root_available,
which does not need a temporary struct kvm_mmu_root_info anymore.
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When using KVM_DIRTY_LOG_INITIALLY_SET, huge pages are not
write-protected when dirty logging is enabled on the memslot. Instead
they are write-protected once userspace invokes KVM_CLEAR_DIRTY_LOG for
the first time and only for the specific sub-region being cleared.
Enhance KVM_CLEAR_DIRTY_LOG to also try to split huge pages prior to
write-protecting to avoid causing write-protection faults on vCPU
threads. This also allows userspace to smear the cost of huge page
splitting across multiple ioctls, rather than splitting the entire
memslot as is the case when initially-all-set is not used.
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220119230739.2234394-17-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When dirty logging is enabled without initially-all-set, try to split
all huge pages in the memslot down to 4KB pages so that vCPUs do not
have to take expensive write-protection faults to split huge pages.
Eager page splitting is best-effort only. This commit only adds the
support for the TDP MMU, and even there splitting may fail due to out
of memory conditions. Failures to split a huge page is fine from a
correctness standpoint because KVM will always follow up splitting by
write-protecting any remaining huge pages.
Eager page splitting moves the cost of splitting huge pages off of the
vCPU threads and onto the thread enabling dirty logging on the memslot.
This is useful because:
1. Splitting on the vCPU thread interrupts vCPUs execution and is
disruptive to customers whereas splitting on VM ioctl threads can
run in parallel with vCPU execution.
2. Splitting all huge pages at once is more efficient because it does
not require performing VM-exit handling or walking the page table for
every 4KiB page in the memslot, and greatly reduces the amount of
contention on the mmu_lock.
For example, when running dirty_log_perf_test with 96 virtual CPUs, 1GiB
per vCPU, and 1GiB HugeTLB memory, the time it takes vCPUs to write to
all of their memory after dirty logging is enabled decreased by 95% from
2.94s to 0.14s.
Eager Page Splitting is over 100x more efficient than the current
implementation of splitting on fault under the read lock. For example,
taking the same workload as above, Eager Page Splitting reduced the CPU
required to split all huge pages from ~270 CPU-seconds ((2.94s - 0.14s)
* 96 vCPU threads) to only 1.55 CPU-seconds.
Eager page splitting does increase the amount of time it takes to enable
dirty logging since it has split all huge pages. For example, the time
it took to enable dirty logging in the 96GiB region of the
aforementioned test increased from 0.001s to 1.55s.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220119230739.2234394-16-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The "struct kvm *kvm" parameter of kvm_tdp_mmu_get_root() is not used,
so remove it. No functional change intended.
Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
Message-Id: <20220125095909.38122-5-cloudliang@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move the check for an invalid root out of kvm_tdp_mmu_get_root() and into
the one place it actually matters, tdp_mmu_next_root(), as the other user
already has an implicit validity check. A future bug fix will need to
get references to invalid roots to honor mmu_notifier requests; there's
no point in forcing what will be a common path to open code getting a
reference to a root.
No functional change intended.
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211215011557.399940-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Drop the "flush" param and return values to/from the TDP MMU's helper for
zapping collapsible SPTEs. Because the helper runs with mmu_lock held
for read, not write, it uses tdp_mmu_zap_spte_atomic(), and the atomic
zap handles the necessary remote TLB flush.
Similarly, because mmu_lock is dropped and re-acquired between zapping
legacy MMUs and zapping TDP MMUs, kvm_mmu_zap_collapsible_sptes() must
handle remote TLB flushes from the legacy MMU before calling into the TDP
MMU.
Fixes: e2209710cc ("KVM: x86/mmu: Skip rmap operations if rmaps not allocated")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211120045046.3940942-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Unify the flags for rmaps and page tracking data, using a
single flag in struct kvm_arch and a single loop to go
over all the address spaces and memslots. This avoids
code duplication between alloc_all_memslots_rmaps and
kvm_page_track_enable_mmu_write_tracking.
Signed-off-by: David Stevens <stevensd@chromium.org>
[This patch is the delta between David's v2 and v3, with conflicts
fixed and my own commit message. - Paolo]
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Pass struct kvm_page_fault to kvm_tdp_mmu_map() instead of
extracting the arguments from the struct.
Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This together with the next patch will fix a future race between
kvm_zap_gfn_range and the page fault handler, which will happen
when AVIC memslot is going to be only partially disabled.
The performance impact is minimal since kvm_zap_gfn_range is only
called by users, update_mtrr() and kvm_post_set_cr0().
Both only use it if the guest has non-coherent DMA, in order to
honor the guest's UC memtype.
MTRR and CD setup only happens at boot, and generally in an area
where the page tables should be small (for CD) or should not
include the affected GFNs at all (for MTRRs).
This is based on a patch suggested by Sean Christopherson:
https://lkml.org/lkml/2021/7/22/1025
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210810205251.424103-2-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
As alluded to in commit f36f3f2846 ("KVM: add "new" argument to
kvm_arch_commit_memory_region"), a bunch of other places where struct
kvm_memory_slot is used, needs to be refactored to preserve the
"const"ness of struct kvm_memory_slot across-the-board.
Signed-off-by: Hamza Mahfooz <someguy@effective-light.com>
Message-Id: <20210713023338.57108-1-someguy@effective-light.com>
[Do not touch body of slot_rmap_walk_init. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Make fast_page_fault interoperate with the TDP MMU by leveraging
walk_shadow_page_lockless_{begin,end} to acquire the RCU read lock and
introducing a new helper function kvm_tdp_mmu_fast_pf_get_last_sptep to
grab the lowest level sptep.
Suggested-by: Ben Gardon <bgardon@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20210713220957.3493520-5-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acquire the RCU read lock in walk_shadow_page_lockless_begin and release
it in walk_shadow_page_lockless_end when the TDP MMU is enabled. This
should not introduce any functional changes but is used in the following
commit to make fast_page_fault interoperate with the TDP MMU.
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20210713220957.3493520-4-dmatlack@google.com>
[Use if...else instead of if(){return;}]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Treat a NULL shadow page in the "is a TDP MMU" check as valid, non-TDP
root. KVM uses a "direct" PAE paging MMU when TDP is disabled and the
guest is running with paging disabled. In that case, root_hpa points at
the pae_root page (of which only 32 bytes are used), not a standard
shadow page, and the WARN fires (a lot).
Fixes: 0b873fd7fb ("KVM: x86/mmu: Remove redundant is_tdp_mmu_enabled check")
Cc: David Matlack <dmatlack@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622072454.3449146-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This change simplifies the call sites slightly and also abstracts away
the implementation detail of looking at root_hpa as the mechanism for
determining if the mmu is the TDP MMU.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20210617231948.2591431-4-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This check is redundant because the root shadow page will only be a TDP
MMU page if is_tdp_mmu_enabled() returns true, and is_tdp_mmu_enabled()
never changes for the lifetime of a VM.
It's possible that this check was added for performance reasons but it
is unlikely that it is useful in practice since to_shadow_page() is
cheap. That being said, this patch also caches the return value of
is_tdp_mmu_root() in direct_page_fault() since there's no reason to
duplicate the call so many times, so performance is not a concern.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20210617231948.2591431-3-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
If is_tdp_mmu_root is not inlined, the elimination of TDP MMU calls as dead
code might not work out. To avoid this, explicitly declare the stubbed
is_tdp_mmu_root on 32-bit hosts.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
TDP MMU iterator's level is identical to page table's actual level. For
instance, for the last level page table (whose entry points to one 4K
page), iter->level is 1 (PG_LEVEL_4K), and in case of 5 level paging,
the iter->level is mmu->shadow_root_level, which is 5. However, struct
kvm_mmu_page's level currently is not set correctly when it is allocated
in kvm_tdp_mmu_map(). When iterator hits non-present SPTE and needs to
allocate a new child page table, currently iter->level, which is the
level of the page table where the non-present SPTE belongs to, is used.
This results in struct kvm_mmu_page's level always having its parent's
level (excpet root table's level, which is initialized explicitly using
mmu->shadow_root_level).
This is kinda wrong, and not consistent with existing non TDP MMU code.
Fortuantely sp->role.level is only used in handle_removed_tdp_mmu_page()
and kvm_tdp_mmu_zap_sp(), and they are already aware of this and behave
correctly. However to make it consistent with legacy MMU code (and fix
the issue that both root page table and its child page table have
shadow_root_level), use iter->level - 1 in kvm_tdp_mmu_map(), and change
handle_removed_tdp_mmu_page() and kvm_tdp_mmu_zap_sp() accordingly.
Reviewed-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Kai Huang <kai.huang@intel.com>
Message-Id: <bcb6569b6e96cb78aaa7b50640e6e6b53291a74e.1623717884.git.kai.huang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
If the TDP MMU is in use, wait to allocate the rmaps until the shadow
MMU is actually used. (i.e. a nested VM is launched.) This saves memory
equal to 0.2% of guest memory in cases where the TDP MMU is used and
there are no nested guests involved.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210518173414.450044-8-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Prepare for write protecting large page lazily during dirty log tracking,
for which we will only need to write protect gfns at large page
granularity.
No functional or performance change expected.
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Message-Id: <20210429034115.35560-2-zhukeqian1@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
To avoid saddling a vCPU thread with the work of tearing down an entire
paging structure, take a reference on each root before they become
obsolete, so that the thread initiating the fast invalidation can tear
down the paging structure and (most likely) release the last reference.
As a bonus, this teardown can happen under the MMU lock in read mode so
as not to block the progress of vCPU threads.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-14-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Provide a real mechanism for fast invalidation by marking roots as
invalid so that their reference count will quickly fall to zero
and they will be torn down.
One negative side affect of this approach is that a vCPU thread will
likely drop the last reference to a root and be saddled with the work of
tearing down an entire paging structure. This issue will be resolved in
a later commit.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-13-bgardon@google.com>
[Move the loop to tdp_mmu.c, otherwise compilation fails on 32-bit. - Paolo]
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
