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KVM: nSVM: Add missing consistency check for EFER, CR0, CR4, and CS

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According to the APM Volume #2, 15.5, Canonicalization and Consistency
Checks (24593—Rev. 3.42—March 2024), the following condition (among
others) results in a #VMEXIT with VMEXIT_INVALID (aka SVM_EXIT_ERR):

  EFER.LME, CR0.PG, CR4.PAE, CS.L, and CS.D are all non-zero.

In the list of consistency checks done when EFER.LME and CR0.PG are set,
add a check that CS.L and CS.D are not both set, after the existing
check that CR4.PAE is set.

This is functionally a nop because the nested VMRUN results in
SVM_EXIT_ERR in HW, which is forwarded to L1, but KVM makes all
consistency checks before a VMRUN is actually attempted.

Fixes: 3d6368ef58 ("KVM: SVM: Add VMRUN handler")
Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-17-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Yosry Ahmed 2026-03-03 00:34:10 +00:00 committed by Sean Christopherson
parent b71138fcc3
commit 96bd3e76a1
2 changed files with 7 additions and 0 deletions
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6
arch/x86/kvm/svm/nested.c
View File

@ -391,6 +391,10 @@ static bool nested_vmcb_check_save(struct kvm_vcpu *vcpu,
CC(!(save->cr0 & X86_CR0_PE)) ||
CC(!kvm_vcpu_is_legal_cr3(vcpu, save->cr3)))
return false;
if (CC((save->cs.attrib & SVM_SELECTOR_L_MASK) &&
(save->cs.attrib & SVM_SELECTOR_DB_MASK)))
return false;
}
/* Note, SVM doesn't have any additional restrictions on CR4. */
@ -486,6 +490,8 @@ static void __nested_copy_vmcb_save_to_cache(struct vmcb_save_area_cached *to,
* Copy only fields that are validated, as we need them
* to avoid TOC/TOU races.
*/
to->cs = from->cs;
to->efer = from->efer;
to->cr0 = from->cr0;
to->cr3 = from->cr3;

1
arch/x86/kvm/svm/svm.h
View File

@ -140,6 +140,7 @@ struct kvm_vmcb_info {
};
struct vmcb_save_area_cached {
struct vmcb_seg cs;
u64 efer;
u64 cr4;
u64 cr3;