Most of the time, calls to get_guest_pgd result in calling
kvm_read_cr3 (the exception is only nested TDP). Hardcode
the default instead of using the get_cr3 function, avoiding
a retpoline if they are enabled.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Link: https://lore.kernel.org/r/20230322013731.102955-2-minipli@grsecurity.net
Signed-off-by: Sean Christopherson <seanjc@google.com>
Sync the spte only when the spte is set and avoid the indirect branch.
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Link: https://lore.kernel.org/r/20230216235321.735214-5-jiangshanlai@gmail.com
[sean: add wrapper instead of open coding each check]
Signed-off-by: Sean Christopherson <seanjc@google.com>
In hardware TLB, invalidating TLB entries means the translations are
removed from the TLB.
In KVM shadowed vTLB, the translations (combinations of shadow paging
and hardware TLB) are generally maintained as long as they remain "clean"
when the TLB of an address space (i.e. a PCID or all) is flushed with
the help of write-protections, sp->unsync, and kvm_sync_page(), where
"clean" in this context means that no updates to KVM's SPTEs are needed.
However, FNAME(invlpg) always zaps/removes the vTLB if the shadow page is
unsync, and thus triggers a remote flush even if the original vTLB entry
is clean, i.e. is usable as-is.
Besides this, FNAME(invlpg) is largely is a duplicate implementation of
FNAME(sync_spte) to invalidate a vTLB entry.
To address both issues, reuse FNAME(sync_spte) to share the code and
slightly modify the semantics, i.e. keep the vTLB entry if it's "clean"
and avoid remote TLB flush.
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Link: https://lore.kernel.org/r/20230216235321.735214-3-jiangshanlai@gmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Don't assume the current root to be valid, just check it and remove
the WARN().
Also move the code to check if the root is valid into FNAME(invlpg)
to simplify the code.
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Link: https://lore.kernel.org/r/20230216235321.735214-2-jiangshanlai@gmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Sometimes when the guest updates its pagetable, it adds only new gptes
to it without changing any existed one, so there is no point to update
the sptes for these existed gptes.
Also when the sptes for these unchanged gptes are updated, the AD
bits are also removed since make_spte() is called with prefetch=true
which might result unneeded TLB flushing.
Just do nothing if the gpte's permissions are unchanged.
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Link: https://lore.kernel.org/r/20230216154115.710033-7-jiangshanlai@gmail.com
[sean: expand comment to call out A/D bits]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Rename mmu->sync_page to mmu->sync_spte and move the code out
of FNAME(sync_page)'s loop body into mmu.c.
No functionalities change intended.
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Link: https://lore.kernel.org/r/20230216154115.710033-6-jiangshanlai@gmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
FNAME(invlpg)() and kvm_mmu_invalidate_gva() take a gva_t, i.e. unsigned
long, as the type of the address to invalidate. On 32-bit kernels, the
upper 32 bits of the GPA will get dropped when an L2 GPA address is
invalidated in the shadowed nested TDP MMU.
Convert it to u64 to fix the problem.
Reported-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Link: https://lore.kernel.org/r/20230216154115.710033-2-jiangshanlai@gmail.com
[sean: tweak changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Drop FNAME(is_self_change_mapping) and instead rely on
kvm_mmu_hugepage_adjust() to adjust the hugepage accordingly. Prior to
commit 4cd071d13c ("KVM: x86/mmu: Move calls to thp_adjust() down a
level"), the hugepage adjustment was done before allocating new shadow
pages, i.e. failed to restrict the hugepage sizes if a new shadow page
resulted in account_shadowed() changing the disallowed hugepage tracking.
Removing FNAME(is_self_change_mapping) fixes a bug reported by Huang Hang
where KVM unnecessarily forces a 4KiB page. FNAME(is_self_change_mapping)
has a defect in that it blindly disables _all_ hugepage mappings rather
than trying to reduce the size of the hugepage. If the guest is writing
to a 1GiB page and the 1GiB is self-referential but a 2MiB page is not,
then KVM can and should create a 2MiB mapping.
Add a comment above the call to kvm_mmu_hugepage_adjust() to call out the
new dependency on adjusting the hugepage size after walking indirect PTEs.
Reported-by: Huang Hang <hhuang@linux.alibaba.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Link: https://lore.kernel.org/r/20221213125538.81209-1-jiangshanlai@gmail.com
[sean: rework changelog after separating out the emulator change]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230202182817.407394-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move the detection of write #PF to shadow pages, i.e. a fault on a write
to a page table that is being shadowed by KVM that is used to translate
the write itself, from FNAME(is_self_change_mapping) to FNAME(fetch).
There is no need to detect the self-referential write before
kvm_faultin_pfn() as KVM does not consume EMULTYPE_WRITE_PF_TO_SP for
accesses that resolve to "error or no-slot" pfns, i.e. KVM doesn't allow
retrying MMIO accesses or writes to read-only memslots.
Detecting the EMULTYPE_WRITE_PF_TO_SP scenario in FNAME(fetch) will allow
dropping FNAME(is_self_change_mapping) entirely, as the hugepage
interaction can be deferred to kvm_mmu_hugepage_adjust().
Cc: Huang Hang <hhuang@linux.alibaba.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Link: https://lore.kernel.org/r/20221213125538.81209-1-jiangshanlai@gmail.com
[sean: split to separate patch, write changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230202182817.407394-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use a new EMULTYPE flag, EMULTYPE_WRITE_PF_TO_SP, to track page faults
on self-changing writes to shadowed page tables instead of propagating
that information to the emulator via a semi-persistent vCPU flag. Using
a flag in "struct kvm_vcpu_arch" is confusing, especially as implemented,
as it's not at all obvious that clearing the flag only when emulation
actually occurs is correct.
E.g. if KVM sets the flag and then retries the fault without ever getting
to the emulator, the flag will be left set for future calls into the
emulator. But because the flag is consumed if and only if both
EMULTYPE_PF and EMULTYPE_ALLOW_RETRY_PF are set, and because
EMULTYPE_ALLOW_RETRY_PF is deliberately not set for direct MMUs, emulated
MMIO, or while L2 is active, KVM avoids false positives on a stale flag
since FNAME(page_fault) is guaranteed to be run and refresh the flag
before it's ultimately consumed by the tail end of reexecute_instruction().
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230202182817.407394-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When a spte is dropped, the start gfn of tlb flushing should be the gfn
of spte not the base gfn of SP which contains the spte. Also introduce a
helper function to do range-based flushing when a spte is dropped, which
would help prevent future buggy use of
kvm_flush_remote_tlbs_with_address() in such case.
Fixes: c3134ce240 ("KVM: Replace old tlb flush function with new one to flush a specified range.")
Suggested-by: David Matlack <dmatlack@google.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Link: https://lore.kernel.org/r/72ac2169a261976f00c1703e88cda676dfb960f5.1665214747.git.houwenlong.hwl@antgroup.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Rounding down the GFN to a huge page size is a common pattern throughout
KVM, so move round_gfn_for_level() helper in tdp_iter.c to
mmu_internal.h for common usage. Also rename it as gfn_round_for_level()
to use gfn_* prefix and clean up the other call sites.
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Link: https://lore.kernel.org/r/415c64782f27444898db650e21cf28eeb6441dfa.1665214747.git.houwenlong.hwl@antgroup.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Handle faults on GFNs that do not have a backing memslot in
kvm_faultin_pfn() and drop handle_abnormal_pfn(). This eliminates
duplicate code in the various page fault handlers.
Opportunistically tweak the comment about handling gfn > host.MAXPHYADDR
to reflect that the effect of returning RET_PF_EMULATE at that point is
to avoid creating an MMIO SPTE for such GFNs.
No functional change intended.
Signed-off-by: David Matlack <dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220921173546.2674386-7-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Grab mmu_invalidate_seq in kvm_faultin_pfn() and stash it in struct
kvm_page_fault. The eliminates duplicate code and reduces the amount of
parameters needed for is_page_fault_stale().
Preemptively split out __kvm_faultin_pfn() to a separate function for
use in subsequent commits.
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: <20220921173546.2674386-4-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Rename most of the variables/functions involved in the NX huge page
mitigation to provide consistency, e.g. lpage vs huge page, and NX huge
vs huge NX, and also to provide clarity, e.g. to make it obvious the flag
applies only to the NX huge page mitigation, not to any condition that
prevents creating a huge page.
Add a comment explaining what the newly named "possible_nx_huge_pages"
tracks.
Leave the nx_lpage_splits stat alone as the name is ABI and thus set in
stone.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Mingwei Zhang <mizhang@google.com>
Message-Id: <20221019165618.927057-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tag shadow pages that cannot be replaced with an NX huge page regardless
of whether or not zapping the page would allow KVM to immediately create
a huge page, e.g. because something else prevents creating a huge page.
I.e. track pages that are disallowed from being NX huge pages regardless
of whether or not the page could have been huge at the time of fault.
KVM currently tracks pages that were disallowed from being huge due to
the NX workaround if and only if the page could otherwise be huge. But
that fails to handled the scenario where whatever restriction prevented
KVM from installing a huge page goes away, e.g. if dirty logging is
disabled, the host mapping level changes, etc...
Failure to tag shadow pages appropriately could theoretically lead to
false negatives, e.g. if a fetch fault requests a small page and thus
isn't tracked, and a read/write fault later requests a huge page, KVM
will not reject the huge page as it should.
To avoid yet another flag, initialize the list_head and use list_empty()
to determine whether or not a page is on the list of NX huge pages that
should be recovered.
Note, the TDP MMU accounting is still flawed as fixing the TDP MMU is
more involved due to mmu_lock being held for read. This will be
addressed in a future commit.
Fixes: 5bcaf3e171 ("KVM: x86/mmu: Account NX huge page disallowed iff huge page was requested")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20221019165618.927057-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The motivation of this renaming is to make these variables and related
helper functions less mmu_notifier bound and can also be used for non
mmu_notifier based page invalidation. mmu_invalidate_* was chosen to
better describe the purpose of 'invalidating' a page that those
variables are used for.
- mmu_notifier_seq/range_start/range_end are renamed to
mmu_invalidate_seq/range_start/range_end.
- mmu_notifier_retry{_hva} helper functions are renamed to
mmu_invalidate_retry{_hva}.
- mmu_notifier_count is renamed to mmu_invalidate_in_progress to
avoid confusion with mn_active_invalidate_count.
- While here, also update kvm_inc/dec_notifier_count() to
kvm_mmu_invalidate_begin/end() to match the change for
mmu_notifier_count.
No functional change intended.
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
Message-Id: <20220816125322.1110439-3-chao.p.peng@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add spte_index() to dedup all the code that calculates a SPTE's index
into its parent's page table and/or spt array. Opportunistically tweak
the calculation to avoid pointer arithmetic, which is subtle (subtract in
8-byte chunks) and less performant (requires the compiler to generate the
subtraction).
Suggested-by: David Matlack <dmatlack@google.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220712020724.1262121-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The result of gva_to_gpa() is physical address not virtual address,
it is odd that UNMAPPED_GVA macro is used as the result for physical
address. Replace UNMAPPED_GVA with INVALID_GPA and drop UNMAPPED_GVA
macro.
No functional change intended.
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/6104978956449467d3c68f1ad7f2c2f6d771d0ee.1656667239.git.houwenlong.hwl@antgroup.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Before allocating a child shadow page table, all callers check
whether the parent already points to a huge page and, if so, they
drop that SPTE. This is done by drop_large_spte().
However, dropping the large SPTE is really only necessary before the
sp is installed. While the sp is returned by kvm_mmu_get_child_sp(),
installing it happens later in __link_shadow_page(). Move the call
there instead of having it in each and every caller.
To ensure that the shadow page is not linked twice if it was present,
do _not_ opportunistically make kvm_mmu_get_child_sp() idempotent:
instead, return an error value if the shadow page already existed.
This is a bit more verbose, but clearer than NULL.
Finally, now that the drop_large_spte() name is not taken anymore,
remove the two underscores in front of __drop_large_spte().
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Splitting huge pages requires allocating/finding shadow pages to replace
the huge page. Shadow pages are keyed, in part, off the guest access
permissions they are shadowing. For fully direct MMUs, there is no
shadowing so the access bits in the shadow page role are always ACC_ALL.
But during shadow paging, the guest can enforce whatever access
permissions it wants.
In particular, eager page splitting needs to know the permissions to use
for the subpages, but KVM cannot retrieve them from the guest page
tables because eager page splitting does not have a vCPU. Fortunately,
the guest access permissions are easy to cache whenever page faults or
FNAME(sync_page) update the shadow page tables; this is an extension of
the existing cache of the shadowed GFNs in the gfns array of the shadow
page. The access bits only take up 3 bits, which leaves 61 bits left
over for gfns, which is more than enough.
Now that the gfns array caches more information than just GFNs, rename
it to shadowed_translation.
While here, preemptively fix up the WARN_ON() that detects gfn
mismatches in direct SPs. The WARN_ON() was paired with a
pr_err_ratelimited(), which means that users could sometimes see the
WARN without the accompanying error message. Fix this by outputting the
error message as part of the WARN splat, and opportunistically make
them WARN_ONCE() because if these ever fire, they are all but guaranteed
to fire a lot and will bring down the kernel.
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220516232138.1783324-18-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Instead of computing the shadow page role from scratch for every new
page, derive most of the information from the parent shadow page. This
eliminates the dependency on the vCPU root role to allocate shadow page
tables, and reduces the number of parameters to kvm_mmu_get_page().
Preemptively split out the role calculation to a separate function for
use in a following commit.
Note that when calculating the MMU root role, we can take
@role.passthrough, @role.direct, and @role.access directly from
@vcpu->arch.mmu->root_role. Only @role.level and @role.quadrant still
must be overridden for PAE page directories, when shadowing 32-bit
guest page tables with PAE page tables.
No functional change intended.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220516232138.1783324-5-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use common logic for computing PT_BASE_ADDR_MASK for 32-bit, 64-bit, and
EPT paging. Both PAGE_MASK and the new-common logic are supsersets of
what is actually needed for 32-bit paging. PAGE_MASK sets bits 63:12 and
the former GUEST_PT64_BASE_ADDR_MASK sets bits 51:12, so regardless of
which value is used, the result will always be bits 31:12.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220614233328.3896033-9-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Truncate paging32's PT_BASE_ADDR_MASK to a pt_element_t, i.e. to 32 bits.
Ignoring PSE huge pages, the mask is only used in conjunction with gPTEs,
which are 32 bits, and so the address is limited to bits 31:12.
PSE huge pages encoded PA bits 39:32 in PTE bits 20:13, i.e. need custom
logic to handle their funky encoding regardless of PT_BASE_ADDR_MASK.
Note, PT_LVL_OFFSET_MASK is somewhat confusing in that it computes the
offset of the _gfn_, not of the gpa, i.e. not having bits 63:32 set in
PT_BASE_ADDR_MASK is again correct.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220614233328.3896033-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Dedup the code for generating (most of) the per-type PT_* masks in
paging_tmpl.h. The relevant macros only vary based on the number of bits
per level, and that smidge of info is already provided in a common form
as PT_LEVEL_BITS.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220614233328.3896033-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Separate the macros for KVM's shadow PTEs (SPTE) from guest 64-bit PTEs
(PT64). SPTE and PT64 are _mostly_ the same, but the few differences are
quite critical, e.g. *_BASE_ADDR_MASK must differentiate between host and
guest physical address spaces, and SPTE_PERM_MASK (was PT64_PERM_MASK) is
very much specific to SPTEs.
Opportunistically (and temporarily) move most guest macros into paging.h
to clearly associate them with shadow paging, and to ensure that they're
not used as of this commit. A future patch will eliminate them entirely.
Sadly, PT32_LEVEL_BITS is left behind in mmu_internal.h because it's
needed for the quadrant calculation in kvm_mmu_get_page(). The quadrant
calculation is hot enough (when using shadow paging with 32-bit guests)
that adding a per-context helper is undesirable, and burying the
computation in paging_tmpl.h with a forward declaration isn't exactly an
improvement.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220614233328.3896033-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move a handful of one-off macros and helpers for 32-bit PSE paging into
paging_tmpl.h and hide them behind "PTTYPE == 32". Under no circumstance
should anything but 32-bit shadow paging care about PSE paging.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220614233328.3896033-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Drop the CMPXCHG macro from paging_tmpl.h, it's no longer used now that
KVM uses a common uaccess helper to do 8-byte CMPXCHG.
Fixes: f122dfe447 ("KVM: x86: Use __try_cmpxchg_user() to update guest PTE A/D bits")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220613225723.2734132-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a comment to FNAME(sync_page) to explain why the TLB flushing logic
conspiculously doesn't handle the scenario of guest protections being
reduced. Specifically, if synchronizing a SPTE drops execute protections,
KVM will not emit a TLB flush, whereas dropping writable or clearing A/D
bits does trigger a flush via mmu_spte_update(). Architecturally, until
the GPTE is implicitly or explicitly flushed from the guest's perspective,
KVM is not required to flush any old, stale translations.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Message-Id: <20220513195000.99371-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
All of sync_page()'s existing checks filter out only !PRESENT gPTE,
because without execute-only, all upper levels are guaranteed to be at
least READABLE. However, if EPT with execute-only support is in use by
L1, KVM can create an SPTE that is shadow-present but guest-inaccessible
(RWX=0) if the upper level combined permissions are R (or RW) and
the leaf EPTE is changed from R (or RW) to X. Because the EPTE is
considered present when viewed in isolation, and no reserved bits are set,
FNAME(prefetch_invalid_gpte) will consider the GPTE valid, and cause a
not-present SPTE to be created.
The SPTE is "correct": the guest translation is inaccessible because
the combined protections of all levels yield RWX=0, and KVM will just
redirect any vmexits to the guest. If EPT A/D bits are disabled, KVM
can mistake the SPTE for an access-tracked SPTE, but again such confusion
isn't fatal, as the "saved" protections are also RWX=0. However,
creating a useless SPTE in general means that KVM messed up something,
even if this particular goof didn't manifest as a functional bug.
So, drop SPTEs whose new protections will yield a RWX=0 SPTE, and
add a WARN in make_spte() to detect creation of SPTEs that will
result in RWX=0 protections.
Fixes: d95c55687e ("kvm: mmu: track read permission explicitly for shadow EPT page tables")
Cc: David Matlack <dmatlack@google.com>
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220513195000.99371-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Expand and clean up the page fault stats. The current stats are at best
incomplete, and at worst misleading. Differentiate between faults that
are actually fixed vs those that result in an MMIO SPTE being created,
track faults that are spurious, faults that trigger emulation, faults
that that are fixed in the fast path, and last but not least, track the
number of faults that are taken.
Note, the number of faults that require emulation for write-protected
shadow pages can roughly be calculated by subtracting the number of MMIO
SPTEs created from the overall number of faults that trigger emulation.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220423034752.1161007-10-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add RET_PF_CONTINUE and use it in handle_abnormal_pfn() and
kvm_faultin_pfn() to signal that the page fault handler should continue
doing its thing. Aside from being gross and inefficient, using a boolean
return to signal continue vs. stop makes it extremely difficult to add
more helpers and/or move existing code to a helper.
E.g. hypothetically, if nested MMUs were to gain a separate page fault
handler in the future, everything up to the "is self-modifying PTE" check
can be shared by all shadow MMUs, but communicating up the stack whether
to continue on or stop becomes a nightmare.
More concretely, proposed support for private guest memory ran into a
similar issue, where it'll be forced to forego a helper in order to yield
sane code: https://lore.kernel.org/all/YkJbxiL%2FAz7olWlq@google.com.
No functional change intended.
Cc: David Matlack <dmatlack@google.com>
Cc: Chao Peng <chao.p.peng@linux.intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220423034752.1161007-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When shadowing 5-level NPT for 4-level NPT L1 guest, the root_sp is
allocated with role.level = 5 and the guest pagetable's root gfn.
And root_sp->spt[0] is also allocated with the same gfn and the same
role except role.level = 4. Luckily that they are different shadow
pages, but only root_sp->spt[0] is the real translation of the guest
pagetable.
Here comes a problem:
If the guest switches from gCR4_LA57=0 to gCR4_LA57=1 (or vice verse)
and uses the same gfn as the root page for nested NPT before and after
switching gCR4_LA57. The host (hCR4_LA57=1) might use the same root_sp
for the guest even the guest switches gCR4_LA57. The guest will see
unexpected page mapped and L2 may exploit the bug and hurt L1. It is
lucky that the problem can't hurt L0.
And three special cases need to be handled:
The root_sp should be like role.direct=1 sometimes: its contents are
not backed by gptes, root_sp->gfns is meaningless. (For a normal high
level sp in shadow paging, sp->gfns is often unused and kept zero, but
it could be relevant and meaningful if sp->gfns is used because they
are backed by concrete gptes.)
For such root_sp in the case, root_sp is just a portal to contribute
root_sp->spt[0], and root_sp->gfns should not be used and
root_sp->spt[0] should not be dropped if gpte[0] of the guest root
pagetable is changed.
Such root_sp should not be accounted too.
So add role.passthrough to distinguish the shadow pages in the hash
when gCR4_LA57 is toggled and fix above special cases by using it in
kvm_mmu_page_{get|set}_gfn() and sp_has_gptes().
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Message-Id: <20220420131204.2850-3-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Remove another duplicate field of struct kvm_mmu. This time it's
the root level for page table walking; the separate field is
always initialized as cpu_role.base.level, so its users can look
up the CPU mode directly instead.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
mmu_role represents the role of the root of the page tables.
It does not need any extended bits, as those govern only KVM's
page table walking; the is_* functions used for page table
walking always use the CPU role.
ext.valid is not present anymore in the MMU role, but an
all-zero MMU role is impossible because the level field is
never zero in the MMU role. So just zap the whole mmu_role
in order to force invalidation after CPUID is updated.
While making this change, which requires touching almost every
occurrence of "mmu_role", rename it to "root_role".
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The ept_ad field is used during page walk to determine if the guest PTEs
have accessed and dirty bits. In the MMU role, the ad_disabled
bit represents whether the *shadow* PTEs have the bits, so it
would be incorrect to replace PT_HAVE_ACCESSED_DIRTY with just
!mmu->mmu_role.base.ad_disabled.
However, the similar field in the CPU mode, ad_disabled, is initialized
correctly: to the opposite value of ept_ad for shadow EPT, and zero
for non-EPT guest paging modes (which always have A/D bits). It is
therefore possible to compute PT_HAVE_ACCESSED_DIRTY from the CPU mode,
like other page-format fields; it just has to be inverted to account
for the different polarity.
In fact, now that the CPU mode is distinct from the MMU roles, it would
even be possible to remove PT_HAVE_ACCESSED_DIRTY macro altogether, and
use !mmu->cpu_role.base.ad_disabled instead. I am not doing this because
the macro has a small effect in terms of dead code elimination:
text data bss dec hex
103544 16665 112 120321 1d601 # as of this patch
103746 16665 112 120523 1d6cb # without PT_HAVE_ACCESSED_DIRTY
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Snapshot the state of the processor registers that govern page walk into
a new field of struct kvm_mmu. This is a more natural representation
than having it *mostly* in mmu_role but not exclusively; the delta
right now is represented in other fields, such as root_level.
The nested MMU now has only the CPU role; and in fact the new function
kvm_calc_cpu_role is analogous to the previous kvm_calc_nested_mmu_role,
except that it has role.base.direct equal to !CR0.PG. For a walk-only
MMU, "direct" has no meaning, but we set it to !CR0.PG so that
role.ext.cr0_pg can go away in a future patch.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
If accessed bits are not supported there simple isn't any distinction
between accessed and non-accessed gPTEs, so the comment does not make
much sense. Rephrase it in terms of what happens if accessed bits
*are* supported.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the recently introduced __try_cmpxchg_user() to update guest PTE A/D
bits instead of mapping the PTE into kernel address space. The VM_PFNMAP
path is broken as it assumes that vm_pgoff is the base pfn of the mapped
VMA range, which is conceptually wrong as vm_pgoff is the offset relative
to the file and has nothing to do with the pfn. The horrific hack worked
for the original use case (backing guest memory with /dev/mem), but leads
to accessing "random" pfns for pretty much any other VM_PFNMAP case.
Fixes: bd53cb35a3 ("X86/KVM: Handle PFNs outside of kernel reach when touching GPTEs")
Debugged-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Tested-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Reported-by: syzbot+6cde2282daa792c49ab8@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220202004945.2540433-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Derive the mask of RWX bits reported on EPT violations from the mask of
RWX bits that are shoved into EPT entries; the layout is the same, the
EPT violation bits are simply shifted by three. Use the new shift and a
slight copy-paste of the mask derivation instead of completely open
coding the same to convert between the EPT entry bits and the exit
qualification when synthesizing a nested EPT Violation.
No functional change intended.
Cc: SU Hang <darcy.sh@antgroup.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220329030108.97341-3-darcy.sh@antgroup.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Using self-expressing macro definition EPT_VIOLATION_GVA_VALIDATION
and EPT_VIOLATION_GVA_TRANSLATED instead of 0x180
in FNAME(walk_addr_generic)().
Signed-off-by: SU Hang <darcy.sh@antgroup.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220329030108.97341-2-darcy.sh@antgroup.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
FNAME(cmpxchg_gpte) is an inefficient mess. It is at least decent if it
can go through get_user_pages_fast(), but if it cannot then it tries to
use memremap(); that is not just terribly slow, it is also wrong because
it assumes that the VM_PFNMAP VMA is contiguous.
The right way to do it would be to do the same thing as
hva_to_pfn_remapped() does since commit add6a0cd1c ("KVM: MMU: try to
fix up page faults before giving up", 2016-07-05), using follow_pte()
and fixup_user_fault() to determine the correct address to use for
memremap(). To do this, one could for example extract hva_to_pfn()
for use outside virt/kvm/kvm_main.c. But really there is no reason to
do that either, because there is already a perfectly valid address to
do the cmpxchg() on, only it is a userspace address. That means doing
user_access_begin()/user_access_end() and writing the code in assembly
to handle exceptions correctly. Worse, the guest PTE can be 8-byte
even on i686 so there is the extra complication of using cmpxchg8b to
account for. But at least it is an efficient mess.
(Thanks to Linus for suggesting improvement on the inline assembly).
Reported-by: Qiuhao Li <qiuhao@sysec.org>
Reported-by: Gaoning Pan <pgn@zju.edu.cn>
Reported-by: Yongkang Jia <kangel@zju.edu.cn>
Reported-by: syzbot+6cde2282daa792c49ab8@syzkaller.appspotmail.com
Debugged-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Tested-by: Maxim Levitsky <mlevitsk@redhat.com>
Cc: stable@vger.kernel.org
Fixes: bd53cb35a3 ("X86/KVM: Handle PFNs outside of kernel reach when touching GPTEs")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Change the type of access u32 to u64 for FNAME(walk_addr) and
->gva_to_gpa().
The kinds of accesses are usually combinations of UWX, and VMX/SVM's
nested paging adds a new factor of access: is it an access for a guest
page table or for a final guest physical address.
And SMAP relies a factor for supervisor access: explicit or implicit.
So @access in FNAME(walk_addr) and ->gva_to_gpa() is better to include
all these information to do the walk.
Although @access(u32) has enough bits to encode all the kinds, this
patch extends it to u64:
o Extra bits will be in the higher 32 bits, so that we can
easily obtain the traditional access mode (UWX) by converting
it to u32.
o Reuse the value for the access kind defined by SVM's nested
paging (PFERR_GUEST_FINAL_MASK and PFERR_GUEST_PAGE_MASK) as
@error_code in kvm_handle_page_fault().
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Message-Id: <20220311070346.45023-2-jiangshanlai@gmail.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>
Remove mmu_audit.c and all its collateral, the auditing code has suffered
severe bitrot, ironically partly due to shadow paging being more stable
and thus not benefiting as much from auditing, but mostly due to TDP
supplanting shadow paging for non-nested guests and shadowing of nested
TDP not heavily stressing the logic that is being audited.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reduce an indirect function call (retpoline) and some intialization
code.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Message-Id: <20211124122055.64424-4-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
