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KVM: VMX: Synthesize nested EPT violation GVA_IS_VALID/GVA_TRANSLATED bits

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When injecting an EPT Violation into L2 in response to a fault detected
while emulating an L2 GVA access, synthesize the GVA_IS_VALID and
GVA_TRANSLATED bits using information provided by the walker, instead of
pulling the bits from vmcs02.EXIT_QUALIFICATION.  The information in
vmcs02.EXIT_QUALIFICATION is valid/correct if and only if the fault being
injected into L1 is the direct result of an EPT Violation VM-Exit from L2.

E.g. if KVM is emulating an I/O instruction and the memory operand's
translation through L1's EPT fails, using vmcs02.EXIT_QUALIFICATION is
wrong as the semantics for EXIT_QUALIFICATION would be for an I/O exit,
not an EPT Violation exit.

Opportunistically clean up the formatting for creating the mask of bits
to pull from vmcs02.EXIT_QUALIFICATION.

Signed-off-by: Kevin Cheng <chengkev@google.com>
[sean: use plumbed in @access bits, massage changelog]
Link: https://patch.msgid.link/20260522232701.3671446-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Kevin Cheng 2026-05-22 16:27:00 -07:00 committed by Sean Christopherson
parent 297c2fe249
commit 96b067b59a
2 changed files with 33 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
arch/x86/kvm/mmu/paging_tmpl.h
View File

@ -502,7 +502,8 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
* [2:0] - Derive from the access bits. The exit_qualification might be
* out of date if it is serving an EPT misconfiguration.
* [5:3] - Calculated by the page walk of the guest EPT page tables
* [7:11] - Derived from [7:11] of real exit_qualification
* [7:8] - Derived from "fault stage" access bits
* [9:11] - Derived from [9:11] of real exit_qualification
*
* The other bits are set to 0.
*/
@ -516,6 +517,14 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
else
walker->fault.exit_qualification |= EPT_VIOLATION_ACC_READ;
/*
* KVM doesn't emulate features that access GPAs directly, e.g.
* Intel Processor Trace. Assume the GVA is always valid; when
* propagating faults from hardware, KVM will discard this info
* and use the EXIT_QUALIFICATION bits from the VMCS.
*/
walker->fault.exit_qualification |= EPT_VIOLATION_GVA_IS_VALID;
/*
* Accesses to guest paging structures are either "reads" or
* "read+write" accesses, so consider them the latter if write_fault
@ -523,6 +532,8 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
*/
if (access & PFERR_GUEST_PAGE_MASK)
walker->fault.exit_qualification |= EPT_VIOLATION_ACC_READ;
else
walker->fault.exit_qualification |= EPT_VIOLATION_GVA_TRANSLATED;
/*
* Note, pte_access holds the raw RWX bits from the EPTE, not

26
arch/x86/kvm/vmx/nested.c
View File

@ -445,13 +445,29 @@ static void nested_ept_inject_page_fault(struct kvm_vcpu *vcpu,
exit_qualification = 0;
} else {
u64 mask = EPT_VIOLATION_GVA_IS_VALID |
EPT_VIOLATION_GVA_TRANSLATED;
EPT_VIOLATION_GVA_TRANSLATED;
if (vmx->nested.msrs.ept_caps & VMX_EPT_ADVANCED_VMEXIT_INFO_BIT)
mask |= EPT_VIOLATION_GVA_USER |
EPT_VIOLATION_GVA_WRITABLE |
EPT_VIOLATION_GVA_NX;
exit_qualification = fault->exit_qualification;
exit_qualification |= vmx_get_exit_qual(vcpu) & mask;
EPT_VIOLATION_GVA_WRITABLE |
EPT_VIOLATION_GVA_NX;
exit_qualification = fault->exit_qualification & ~mask;
/*
* Use the EXIT_QUALIFICATION from the VMCS if and only
* if the hardware VM-Exit from L2 was an EPT Violation.
* If the fault is synthesized, then EXIT_QUALIFICATION
* is stale and/or holds entirely different data. And
* conversely, KVM _must_ rely on EXIT_QUALIFICATION if
* the fault came from hardware, because KVM only sees
* and walks the faulting GPA.
*/
if (from_hardware)
exit_qualification |= vmx_get_exit_qual(vcpu) & mask;
else
exit_qualification |= fault->exit_qualification & mask;
vm_exit_reason = EXIT_REASON_EPT_VIOLATION;
}