Extract the reserved SPTE check and print helpers in get_mmio_spte() to
new helpers so that KVM can also WARN on reserved badness when making a
SPTE.
Tag the checking helper with __always_inline to improve the probability
of the compiler generating optimal code for the checking loop, e.g. gcc
appears to avoid using %rbp when the helper is tagged with a vanilla
"inline".
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-48-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the MMU's role instead of vCPU state or role_regs to determine the
PTTYPE, i.e. which helpers to wire up.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-47-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Skip paging32E_init_context() and paging64_init_context_common() and go
directly to paging64_init_context() (was the common version) now that
the relevant flows don't need to distinguish between 64-bit PAE and
32-bit PAE for other reasons.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-46-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a helper to calculate the level for non-EPT page tables from the
MMU's role_regs.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-45-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Consolidate MMU guest metadata updates into a common helper for TDP,
shadow, and nested MMUs.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-44-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Don't bother updating the bitmasks and last-leaf information if paging is
disabled as the metadata will never be used.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-43-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move calls to reset_rsvds_bits_mask() out of the various mode statements
and under a more generic CR0.PG=1 check. This will allow for additional
code consolidation in the future.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-42-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Get LA57 from the role_regs, which are initialized from the vCPU even
though TDP is enabled, instead of pulling the value directly from the
vCPU when computing the guest's root_level for TDP MMUs. Note, the check
is inside an is_long_mode() statement, so that requirement is not lost.
Use role_regs even though the MMU's role is available and arguably
"better". A future commit will consolidate the guest root level logic,
and it needs access to EFER.LMA, which is not tracked in the role (it
can't be toggled on VM-Exit, unlike LA57).
Drop is_la57_mode() as there are no remaining users, and to discourage
pulling MMU state from the vCPU (in the future).
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-41-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Initialize the MMU's (guest) root_level using its mmu_role instead of
redoing the calculations. The role_regs used to calculate the mmu_role
are initialized from the vCPU, i.e. this should be a complete nop.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-40-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Drop kvm_mmu.nx as there no consumers left.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-39-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Get the MMU's effective EFER.NX from its role instead of using the
one-off, dedicated flag. This will allow dropping said flag in a
future commit.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-38-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the MMU's role and role_regs to calculate the MMU's guest root level
and NX bit. For some flows, the vCPU state may not be correct (or
relevant), e.g. EPT doesn't interact with EFER.NX and nested NPT will
configure the guest_mmu with possibly-stale vCPU state.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-37-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the NX bit from the MMU's role instead of the MMU itself so that the
redundant, dedicated "nx" flag can be dropped.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-36-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the MMU's role to get CR4.PSE when determining the last level at
which the guest _cannot_ create a non-leaf PTE, i.e. cannot create a
huge page.
Note, the existing logic is arguably wrong when considering 5-level
paging and the case where 1gb pages aren't supported. In practice, the
logic is confusing but not broken, because except for 32-bit non-PAE
paging, bit 7 (_PAGE_PSE) bit is reserved when a huge page isn't supported at
that level. I.e. setting bit 7 will terminate the guest walk one way or
another. Furthermore, last_nonleaf_level is only consulted after KVM has
verified there are no reserved bits set.
All that confusion will be addressed in a future patch by dropping
last_nonleaf_level entirely. For now, massage the code to continue the
march toward using mmu_role for (almost) all MMU computations.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-35-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the MMU's role to calculate the Protection Keys (Restrict Userspace)
bitmask instead of pulling bits from current vCPU state. For some flows,
the vCPU state may not be correct (or relevant), e.g. EPT doesn't
interact with PKRU. Case in point, the "ept" param simply disappears.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-34-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the MMU's role to generate the permission bitmasks for the MMU.
For some flows, the vCPU state may not be correct (or relevant), e.g.
the nested NPT MMU can be initialized with incoherent vCPU state.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-33-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Drop the vCPU param from __reset_rsvds_bits_mask() as it's now unused,
and ideally will remain unused in the future. Any information that's
needed by the low level helper should be explicitly provided as it's used
for both shadow/host MMUs and guest MMUs, i.e. vCPU state may be
meaningless or simply wrong.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-32-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the MMU's role to get CR4.PSE when calculating reserved bits for the
guest's PTEs. Practically speaking, this is a glorified nop as the role
always come from vCPU state for the relevant flows, but converting to
the roles will provide consistency once everything else is converted, and
will Just Work if the "always comes from vCPU" behavior were ever to
change (unlikely).
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-31-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Unconditionally pass pse=false when calculating reserved bits for shadow
PTEs. CR4.PSE is only relevant for 32-bit non-PAE paging, which KVM does
not use for shadow paging (including nested NPT).
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-30-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Refactor shadow MMU initialization to immediately set its new mmu_role
after verifying it differs from the old role, and so that all flavors
of MMU initialization share the same check-and-set pattern. Immediately
setting the role will allow future commits to use mmu_role to configure
the MMU without consuming stale state.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-29-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Don't set cr4_pke or cr4_la57 in the MMU role if long mode isn't active,
which is required for protection keys and 5-level paging to be fully
enabled. Ignoring the bit avoids unnecessary reconfiguration on reuse,
and also means consumers of mmu_role don't need to manually check for
long mode.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-28-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Don't set CR0/CR4/EFER bits in the MMU role if paging is disabled, paging
modifiers are irrelevant if there is no paging in the first place.
Somewhat arbitrarily clear gpte_is_8_bytes for shadow paging if paging is
disabled in the guest. Again, there are no guest PTEs to process, so the
size is meaningless.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-27-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add accessors via a builder macro for all mmu_role bits that track a CR0,
CR4, or EFER bit, abstracting whether the bits are in the base or the
extended role.
Future commits will switch to using mmu_role instead of vCPU state to
configure the MMU, i.e. there are about to be a large number of users.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-26-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Rename "nxe" to "efer_nx" so that future macro magic can use the pattern
<reg>_<bit> for all CR0, CR4, and EFER bits that included in the role.
Using "efer_nx" also makes it clear that the role bit reflects EFER.NX,
not the NX bit in the corresponding PTE.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-25-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the provided role_regs to calculate the mmu_role instead of pulling
bits from current vCPU state. For some flows, e.g. nested TDP, the vCPU
state may not be correct (or relevant).
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-24-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Do not incorporate CR0/CR4 bits into the role for the nested EPT MMU, as
EPT behavior is not influenced by CR0/CR4. Note, this is the guest_mmu,
(L1's EPT), not nested_mmu (L2's IA32 paging); the nested_mmu does need
CR0/CR4, and is initialized in a separate flow.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-23-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Consolidate the MMU metadata update calls to deduplicate code, and to
prep for future cleanup.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-22-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Introduce "struct kvm_mmu_role_regs" to hold the register state that is
incorporated into the mmu_role. For nested TDP, the register state that
is factored into the MMU isn't vCPU state; the dedicated struct will be
used to propagate the correct state throughout the flows without having
to pass multiple params, and also provides helpers for the various flag
accessors.
Intentionally make the new helpers cumbersome/ugly by prepending four
underscores. In the not-too-distant future, it will be preferable to use
the mmu_role to query bits as the mmu_role can drop irrelevant bits
without creating contradictions, e.g. clearing CR4 bits when CR0.PG=0.
Reserve the clean helper names (no underscores) for the mmu_role.
Add a helper for vCPU conversion, which is the common case.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-21-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the mmu_role to initialize shadow root level instead of assuming the
level of KVM's shadow root (host) is the same as that of the guest root,
or in the case of 32-bit non-PAE paging where KVM forces PAE paging.
For nested NPT, the shadow root level cannot be adapted to L1's NPT root
level and is instead always the TDP root level because NPT uses the
current host CR0/CR4/EFER, e.g. 64-bit KVM can't drop into 32-bit PAE to
shadow L1's NPT.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-20-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move nested NPT's invocation of reset_shadow_zero_bits_mask() into the
MMU proper and unexport said function. Aside from dropping an export,
this is a baby step toward eliminating the call entirely by fixing the
shadow_root_level confusion.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-19-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Grab all CR0/CR4 MMU role bits from current vCPU state when initializing
a non-nested shadow MMU. Extract the masks from kvm_post_set_cr{0,4}(),
as the CR0/CR4 update masks must exactly match the mmu_role bits, with
one exception (see below). The "full" CR0/CR4 will be used by future
commits to initialize the MMU and its role, as opposed to the current
approach of pulling everything from vCPU, which is incorrect for certain
flows, e.g. nested NPT.
CR4.LA57 is an exception, as it can be toggled on VM-Exit (for L1's MMU)
but can't be toggled via MOV CR4 while long mode is active. I.e. LA57
needs to be in the mmu_role, but technically doesn't need to be checked
by kvm_post_set_cr4(). However, the extra check is completely benign as
the hardware restrictions simply mean LA57 will never be _the_ cause of
a MMU reset during MOV CR4.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-18-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Drop the smep_andnot_wp role check from the "uses NX" calculation now
that all non-nested shadow MMUs treat NX as used via the !TDP check.
The shadow MMU for nested NPT, which shares the helper, does not need to
deal with SMEP (or WP) as NPT walks are always "user" accesses and WP is
explicitly noted as being ignored:
Table walks for guest page tables are always treated as user writes at
the nested page table level.
A table walk for the guest page itself is always treated as a user
access at the nested page table level
The host hCR0.WP bit is ignored under nested paging.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-17-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a comment in the nested NPT initialization flow to call out that it
intentionally uses vmcb01 instead current vCPU state to get the effective
hCR4 and hEFER for L1's NPT context.
Note, despite nSVM's efforts to handle the case where vCPU state doesn't
reflect L1 state, the MMU may still do the wrong thing due to pulling
state from the vCPU instead of the passed in CR0/CR4/EFER values. This
will be addressed in future commits.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-16-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When configuring KVM's MMU, pass CR0 and CR4 as unsigned longs, and EFER
as a u64 in various flows (mostly MMU). Passing the params as u32s is
functionally ok since all of the affected registers reserve bits 63:32 to
zero (enforced by KVM), but it's technically wrong.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-15-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Rename mmu_need_write_protect() to mmu_try_to_unsync_pages() and update
a variety of related, stale comments. Add several new comments to call
out subtle details, e.g. that upper-level shadow pages are write-tracked,
and that can_unsync is false iff KVM is in the process of synchronizing
pages.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-14-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Nove the kvm_unlink_unsync_page() call out of kvm_sync_page() and into
it's sole caller, and fold __kvm_sync_page() into kvm_sync_page() since
the latter becomes a pure pass-through. There really should be no reason
for code to do a complete sync of a shadow page outside of the full
kvm_mmu_sync_roots(), e.g. the one use case that creeped in turned out to
be flawed and counter-productive.
Drop the stale comment about @sp->gfn needing to be write-protected, as
it directly contradicts the kvm_mmu_get_page() usage.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-13-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Explain the usage of sync_page() in kvm_mmu_get_page(), which is
subtle in how and why it differs from mmu_sync_children().
Signed-off-by: Sean Christopherson <seanjc@google.com>
[Split out of a different patch by Sean. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When synchronizing a shadow page, WARN and zap the page if its mmu role
isn't compatible with the current MMU context, where "compatible" is an
exact match sans the bits that have no meaning in the overall MMU context
or will be explicitly overwritten during the sync. Many of the helpers
used by sync_page() are specific to the current context, updating a SMM
vs. non-SMM shadow page would use the wrong memslots, updating L1 vs. L2
PTEs might work but would be extremely bizaree, and so on and so forth.
Drop the guard with respect to 8-byte vs. 4-byte PTEs in
__kvm_sync_page(), it was made useless when kvm_mmu_get_page() stopped
trying to sync shadow pages irrespective of the current MMU context.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-12-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Originally, __kvm_sync_page used to check the cr4_pae bit in the role
to avoid zapping 4-byte kvm_mmu_pages when guest page size are 8-byte
or the other way round. However, in commit 47c42e6b41 ("KVM: x86: fix
handling of role.cr4_pae and rename it to 'gpte_size'", 2019-03-28) it
was observed that this did not work for nested EPT, where the page table
size would be 8 bytes even if CR4.PAE=0. (Note that the check still
has to be done for nested *NPT*, so it is not possible to use tdp_enabled
or similar).
Therefore, a hack was introduced to identify nested EPT shadow pages
and unconditionally call __kvm_sync_page() on them. However, it is
possible to do without the hack to identify nested EPT shadow pages:
if EPT is active, there will be no shadow pages in non-EPT format,
and all of them will have gpte_is_8_bytes set to true; we can just
check the MMU role directly, and the test will always be true.
Even for non-EPT shadow MMUs, this test should really always be true
now that __kvm_sync_page() is called if and only if the role is an
exact match (kvm_mmu_get_page()) or is part of the current MMU context
(kvm_mmu_sync_roots()). A future commit will convert the likely-pointless
check into a meaningful WARN to enforce that the mmu_roles of the current
context and the shadow page are compatible.
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When creating a new upper-level shadow page, zap unsync shadow pages at
the same target gfn instead of attempting to sync the pages. This fixes
a bug where an unsync shadow page could be sync'd with an incompatible
context, e.g. wrong smm, is_guest, etc... flags. In practice, the bug is
relatively benign as sync_page() is all but guaranteed to fail its check
that the guest's desired gfn (for the to-be-sync'd page) matches the
current gfn associated with the shadow page. I.e. kvm_sync_page() would
end up zapping the page anyways.
Alternatively, __kvm_sync_page() could be modified to explicitly verify
the mmu_role of the unsync shadow page is compatible with the current MMU
context. But, except for this specific case, __kvm_sync_page() is called
iff the page is compatible, e.g. the transient sync in kvm_mmu_get_page()
requires an exact role match, and the call from kvm_sync_mmu_roots() is
only synchronizing shadow pages from the current MMU (which better be
compatible or KVM has problems). And as described above, attempting to
sync shadow pages when creating an upper-level shadow page is unlikely
to succeed, e.g. zero successful syncs were observed when running Linux
guests despite over a million attempts.
Fixes: 9f1a122f97 ("KVM: MMU: allow more page become unsync at getting sp time")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-10-seanjc@google.com>
[Remove WARN_ON after __kvm_sync_page. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Drop MAXPHYADDR from mmu_role now that all MMUs have their role
invalidated after a CPUID update. Invalidating the role forces all MMUs
to re-evaluate the guest's MAXPHYADDR, and the guest's MAXPHYADDR can
only be changed only through a CPUID update.
This reverts commit de3ccd26fa.
Cc: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-9-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Warn userspace that KVM_SET_CPUID{,2} after KVM_RUN "may" cause guest
instability. Initialize last_vmentry_cpu to -1 and use it to detect if
the vCPU has been run at least once when its CPUID model is changed.
KVM does not correctly handle changes to paging related settings in the
guest's vCPU model after KVM_RUN, e.g. MAXPHYADDR, GBPAGES, etc... KVM
could theoretically zap all shadow pages, but actually making that happen
is a mess due to lock inversion (vcpu->mutex is held). And even then,
updating paging settings on the fly would only work if all vCPUs are
stopped, updated in concert with identical settings, then restarted.
To support running vCPUs with different vCPU models (that affect paging),
KVM would need to track all relevant information in kvm_mmu_page_role.
Note, that's the _page_ role, not the full mmu_role. Updating mmu_role
isn't sufficient as a vCPU can reuse a shadow page translation that was
created by a vCPU with different settings and thus completely skip the
reserved bit checks (that are tied to CPUID).
Tracking CPUID state in kvm_mmu_page_role is _extremely_ undesirable as
it would require doubling gfn_track from a u16 to a u32, i.e. would
increase KVM's memory footprint by 2 bytes for every 4kb of guest memory.
E.g. MAXPHYADDR (6 bits), GBPAGES, AMD vs. INTEL = 1 bit, and SEV C-BIT
would all need to be tracked.
In practice, there is no remotely sane use case for changing any paging
related CPUID entries on the fly, so just sweep it under the rug (after
yelling at userspace).
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Invalidate all MMUs' roles after a CPUID update to force reinitizliation
of the MMU context/helpers. Despite the efforts of commit de3ccd26fa
("KVM: MMU: record maximum physical address width in kvm_mmu_extended_role"),
there are still a handful of CPUID-based properties that affect MMU
behavior but are not incorporated into mmu_role. E.g. 1gb hugepage
support, AMD vs. Intel handling of bit 8, and SEV's C-Bit location all
factor into the guest's reserved PTE bits.
The obvious alternative would be to add all such properties to mmu_role,
but doing so provides no benefit over simply forcing a reinitialization
on every CPUID update, as setting guest CPUID is a rare operation.
Note, reinitializing all MMUs after a CPUID update does not fix all of
KVM's woes. Specifically, kvm_mmu_page_role doesn't track the CPUID
properties, which means that a vCPU can reuse shadow pages that should
not exist for the new vCPU model, e.g. that map GPAs that are now illegal
(due to MAXPHYADDR changes) or that set bits that are now reserved
(PAGE_SIZE for 1gb pages), etc...
Tracking the relevant CPUID properties in kvm_mmu_page_role would address
the majority of problems, but fully tracking that much state in the
shadow page role comes with an unpalatable cost as it would require a
non-trivial increase in KVM's memory footprint. The GBPAGES case is even
worse, as neither Intel nor AMD provides a way to disable 1gb hugepage
support in the hardware page walker, i.e. it's a virtualization hole that
can't be closed when using TDP.
In other words, resetting the MMU after a CPUID update is largely a
superficial fix. But, it will allow reverting the tracking of MAXPHYADDR
in the mmu_role, and that case in particular needs to mostly work because
KVM's shadow_root_level depends on guest MAXPHYADDR when 5-level paging
is supported. For cases where KVM botches guest behavior, the damage is
limited to that guest. But for the shadow_root_level, a misconfigured
MMU can cause KVM to incorrectly access memory, e.g. due to walking off
the end of its shadow page tables.
Fixes: 7dcd575520 ("x86/kvm/mmu: check if tdp/shadow MMU reconfiguration is needed")
Cc: Yu Zhang <yu.c.zhang@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Restore CR4.LA57 to the mmu_role to fix an amusing edge case with nested
virtualization. When KVM (L0) is using TDP, CR4.LA57 is not reflected in
mmu_role.base.level because that tracks the shadow root level, i.e. TDP
level. Normally, this is not an issue because LA57 can't be toggled
while long mode is active, i.e. the guest has to first disable paging,
then toggle LA57, then re-enable paging, thus ensuring an MMU
reinitialization.
But if L1 is crafty, it can load a new CR4 on VM-Exit and toggle LA57
without having to bounce through an unpaged section. L1 can also load a
new CR3 on exit, i.e. it doesn't even need to play crazy paging games, a
single entry PML5 is sufficient. Such shenanigans are only problematic
if L0 and L1 use TDP, otherwise L1 and L2 share an MMU that gets
reinitialized on nested VM-Enter/VM-Exit due to mmu_role.base.guest_mode.
Note, in the L2 case with nested TDP, even though L1 can switch between
L2s with different LA57 settings, thus bypassing the paging requirement,
in that case KVM's nested_mmu will track LA57 in base.level.
This reverts commit 8053f924ca.
Fixes: 8053f924ca ("KVM: x86/mmu: Drop kvm_mmu_extended_role.cr4_la57 hack")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the MMU's role to get its effective SMEP value when injecting a fault
into the guest. When walking L1's (nested) NPT while L2 is active, vCPU
state will reflect L2, whereas NPT uses the host's (L1 in this case) CR0,
CR4, EFER, etc... If L1 and L2 have different settings for SMEP and
L1 does not have EFER.NX=1, this can result in an incorrect PFEC.FETCH
when injecting #NPF.
Fixes: e57d4a356a ("KVM: Add instruction fetch checking when walking guest page table")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reset the MMU context at vCPU INIT (and RESET for good measure) if CR0.PG
was set prior to INIT. Simply re-initializing the current MMU is not
sufficient as the current root HPA may not be usable in the new context.
E.g. if TDP is disabled and INIT arrives while the vCPU is in long mode,
KVM will fail to switch to the 32-bit pae_root and bomb on the next
VM-Enter due to running with a 64-bit CR3 in 32-bit mode.
This bug was papered over in both VMX and SVM, but still managed to rear
its head in the MMU role on VMX. Because EFER.LMA=1 requires CR0.PG=1,
kvm_calc_shadow_mmu_root_page_role() checks for EFER.LMA without first
checking CR0.PG. VMX's RESET/INIT flow writes CR0 before EFER, and so
an INIT with the vCPU in 64-bit mode will cause the hack-a-fix to
generate the wrong MMU role.
In VMX, the INIT issue is specific to running without unrestricted guest
since unrestricted guest is available if and only if EPT is enabled.
Commit 8668a3c468 ("KVM: VMX: Reset mmu context when entering real
mode") resolved the issue by forcing a reset when entering emulated real
mode.
In SVM, commit ebae871a50 ("kvm: svm: reset mmu on VCPU reset") forced
a MMU reset on every INIT to workaround the flaw in common x86. Note, at
the time the bug was fixed, the SVM problem was exacerbated by a complete
lack of a CR4 update.
The vendor resets will be reverted in future patches, primarily to aid
bisection in case there are non-INIT flows that rely on the existing VMX
logic.
Because CR0.PG is unconditionally cleared on INIT, and because CR0.WP and
all CR4/EFER paging bits are ignored if CR0.PG=0, simply checking that
CR0.PG was '1' prior to INIT/RESET is sufficient to detect a required MMU
context reset.
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Mark NX as being used for all non-nested shadow MMUs, as KVM will set the
NX bit for huge SPTEs if the iTLB mutli-hit mitigation is enabled.
Checking the mitigation itself is not sufficient as it can be toggled on
at any time and KVM doesn't reset MMU contexts when that happens. KVM
could reset the contexts, but that would require purging all SPTEs in all
MMUs, for no real benefit. And, KVM already forces EFER.NX=1 when TDP is
disabled (for WP=0, SMEP=1, NX=0), so technically NX is never reserved
for shadow MMUs.
Fixes: b8e8c8303f ("kvm: mmu: ITLB_MULTIHIT mitigation")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Remove a misguided WARN that attempts to detect the scenario where using
a special A/D tracking flag will set reserved bits on a non-MMIO spte.
The WARN triggers false positives when using EPT with 32-bit KVM because
of the !64-bit clause, which is just flat out wrong. The whole A/D
tracking goo is specific to EPT, and one of the big selling points of EPT
is that EPT is decoupled from the host's native paging mode.
Drop the WARN instead of trying to salvage the check. Keeping a check
specific to A/D tracking bits would essentially regurgitate the same code
that led to KVM needed the tracking bits in the first place.
A better approach would be to add a generic WARN on reserved bits being
set, which would naturally cover the A/D tracking bits, work for all
flavors of paging, and be self-documenting to some extent.
Fixes: 8a406c8953 ("KVM: x86/mmu: Rename and document A/D scheme for TDP SPTEs")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
To remove code duplication, use the binary stats descriptors in the
implementation of the debugfs interface for statistics. This unifies
the definition of statistics for the binary and debugfs interfaces.
Signed-off-by: Jing Zhang <jingzhangos@google.com>
Message-Id: <20210618222709.1858088-8-jingzhangos@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a VCPU ioctl to get a statistics file descriptor by which a read
functionality is provided for userspace to read out VCPU stats header,
descriptors and data.
Define VCPU statistics descriptors and header for all architectures.
Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com> #arm64
Signed-off-by: Jing Zhang <jingzhangos@google.com>
Message-Id: <20210618222709.1858088-5-jingzhangos@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
