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KVM: nSVM: Triple fault if restore host CR3 fails on nested #VMEXIT

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If loading L1's CR3 fails on a nested #VMEXIT, nested_svm_vmexit()
returns an error code that is ignored by most callers, and continues to
run L1 with corrupted state. A sane recovery is not possible in this
case, and HW behavior is to cause a shutdown. Inject a triple fault
instead, and do not return early from nested_svm_vmexit(). Continue
cleaning up the vCPU state (e.g. clear pending exceptions), to handle
the failure as gracefully as possible.

From the APM:

  Upon #VMEXIT, the processor performs the following actions in order to
  return to the host execution context:

  ...

  if (illegal host state loaded, or exception while loading host state)
      shutdown
  else
      execute first host instruction following the VMRUN

Remove the return value of nested_svm_vmexit(), which is mostly
unchecked anyway.

Fixes: d82aaef9c8 ("KVM: nSVM: use nested_svm_load_cr3() on guest->host switch")
CC: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-10-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Yosry Ahmed 2026-03-03 00:34:03 +00:00 committed by Sean Christopherson
parent 1b30e75517
commit 5d291ef058
3 changed files with 8 additions and 19 deletions
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10
arch/x86/kvm/svm/nested.c
View File

@ -1192,12 +1192,11 @@ static int nested_svm_vmexit_update_vmcb12(struct kvm_vcpu *vcpu)
return 0;
}
int nested_svm_vmexit(struct vcpu_svm *svm)
void nested_svm_vmexit(struct vcpu_svm *svm)
{
struct kvm_vcpu *vcpu = &svm->vcpu;
struct vmcb *vmcb01 = svm->vmcb01.ptr;
struct vmcb *vmcb02 = svm->nested.vmcb02.ptr;
int rc;
if (nested_svm_vmexit_update_vmcb12(vcpu))
kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
@ -1316,9 +1315,8 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
nested_svm_uninit_mmu_context(vcpu);
rc = nested_svm_load_cr3(vcpu, vmcb01->save.cr3, false, true);
if (rc)
return 1;
if (nested_svm_load_cr3(vcpu, vmcb01->save.cr3, false, true))
kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
/*
* Drop what we picked up for L2 via svm_complete_interrupts() so it
@ -1343,8 +1341,6 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
*/
if (kvm_apicv_activated(vcpu->kvm))
__kvm_vcpu_update_apicv(vcpu);
return 0;
}
static void nested_svm_triple_fault(struct kvm_vcpu *vcpu)

11
arch/x86/kvm/svm/svm.c
View File

@ -2234,13 +2234,9 @@ static int emulate_svm_instr(struct kvm_vcpu *vcpu, int opcode)
[SVM_INSTR_VMSAVE] = vmsave_interception,
};
struct vcpu_svm *svm = to_svm(vcpu);
int ret;
if (is_guest_mode(vcpu)) {
/* Returns '1' or -errno on failure, '0' on success. */
ret = nested_svm_simple_vmexit(svm, guest_mode_exit_codes[opcode]);
if (ret)
return ret;
nested_svm_simple_vmexit(svm, guest_mode_exit_codes[opcode]);
return 1;
}
return svm_instr_handlers[opcode](vcpu);
@ -4871,7 +4867,6 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
{
struct vcpu_svm *svm = to_svm(vcpu);
struct kvm_host_map map_save;
int ret;
if (!is_guest_mode(vcpu))
return 0;
@ -4891,9 +4886,7 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
svm->vmcb->save.rsp = vcpu->arch.regs[VCPU_REGS_RSP];
svm->vmcb->save.rip = vcpu->arch.regs[VCPU_REGS_RIP];
ret = nested_svm_simple_vmexit(svm, SVM_EXIT_SW);
if (ret)
return ret;
nested_svm_simple_vmexit(svm, SVM_EXIT_SW);
/*
* KVM uses VMCB01 to store L1 host state while L2 runs but

6
arch/x86/kvm/svm/svm.h
View File

@ -793,14 +793,14 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu);
void svm_copy_vmrun_state(struct vmcb_save_area *to_save,
struct vmcb_save_area *from_save);
void svm_copy_vmloadsave_state(struct vmcb *to_vmcb, struct vmcb *from_vmcb);
int nested_svm_vmexit(struct vcpu_svm *svm);
void nested_svm_vmexit(struct vcpu_svm *svm);
static inline int nested_svm_simple_vmexit(struct vcpu_svm *svm, u32 exit_code)
static inline void nested_svm_simple_vmexit(struct vcpu_svm *svm, u32 exit_code)
{
svm->vmcb->control.exit_code = exit_code;
svm->vmcb->control.exit_info_1 = 0;
svm->vmcb->control.exit_info_2 = 0;
return nested_svm_vmexit(svm);
nested_svm_vmexit(svm);
}
int nested_svm_exit_handled(struct vcpu_svm *svm);