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KVM: x86: Fill kvm_run exit fields in common get_nested_state_pages() error paths

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Fill kvm_run with "internal error, emulation" in the common error handling
paths for getting nested state pages, as requiring each check to manually
fill kvm_run is error prone and requires a non-trivial amount of copy+paste.

Specifically, both SVM and VMX fail to fill kvm_run if load_pdptrs() fails,
and SVM fails to fill kvm_run if kvm_hv_verify_vp_assist() fails.  If those
flows fail, the *best* case scenario is that KVM will exit to userspace
with KVM_EXIT_UNKNOWN.  The worst case scenario is that KVM exits with a
stale exit_reason and confuses userspace.

Note, SVM never exits to userspace if something goes sideways when dealing
with vmcb12 assets while emulating VMRUN, i.e. lack of SVM-specific code is
not a bug.

Fixes: 0f85722341 ("KVM: nVMX: delay loading of PDPTRs to KVM_REQ_GET_NESTED_STATE_PAGES")
Fixes: 232f75d3b4 ("KVM: nSVM: call nested_svm_load_cr3 on nested state load")
Fixes: 3f4a812edf ("KVM: nSVM: hyper-v: Enable L2 TLB flush")
Cc: stable@vger.kernel.org
Reported-by: Jinwoo Lee <rkskek9254@gmail.com>
Closes: https://lore.kernel.org/all/20260813043932.3214460-1-rkskek9254@gmail.com
Reported-by: Stefan Teodorescu <fane@google.com>
Link: https://patch.msgid.link/20260921211608.1030158-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2026-09-21 14:16:08 -07:00
parent 10180a2775
commit c1214f293d
3 changed files with 9 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
arch/x86/kvm/svm/nested.c
View File

@ -2125,13 +2125,8 @@ static bool svm_get_nested_state_pages(struct kvm_vcpu *vcpu)
return false;
}
if (!nested_svm_merge_msrpm(vcpu)) {
vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
vcpu->run->internal.suberror =
KVM_INTERNAL_ERROR_EMULATION;
vcpu->run->internal.ndata = 0;
if (!nested_svm_merge_msrpm(vcpu))
return false;
}
if (kvm_hv_verify_vp_assist(vcpu))
return false;

15
arch/x86/kvm/vmx/nested.c
View File

@ -3465,10 +3465,6 @@ static bool nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
} else {
pr_debug_ratelimited("%s: no backing for APIC-access address in vmcs12\n",
__func__);
vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
vcpu->run->internal.suberror =
KVM_INTERNAL_ERROR_EMULATION;
vcpu->run->internal.ndata = 0;
return false;
}
}
@ -3539,11 +3535,6 @@ static bool vmx_get_nested_state_pages(struct kvm_vcpu *vcpu)
if (!nested_get_evmcs_page(vcpu)) {
pr_debug_ratelimited("%s: enlightened vmptrld failed\n",
__func__);
vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
vcpu->run->internal.suberror =
KVM_INTERNAL_ERROR_EMULATION;
vcpu->run->internal.ndata = 0;
return false;
}
#endif
@ -3915,8 +3906,12 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
vmentry_failed:
vcpu->arch.nested_run_pending = 0;
if (status == NVMX_VMENTRY_KVM_INTERNAL_ERROR)
if (status == NVMX_VMENTRY_KVM_INTERNAL_ERROR) {
vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
vcpu->run->internal.ndata = 0;
return 0;
}
if (status == NVMX_VMENTRY_VMEXIT)
return 1;
WARN_ON_ONCE(status != NVMX_VMENTRY_VMFAIL);

3
arch/x86/kvm/x86.c
View File

@ -8072,6 +8072,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) {
if (unlikely(!kvm_nested_call(get_nested_state_pages)(vcpu))) {
vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
vcpu->run->internal.ndata = 0;
kvm_make_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu);
r = 0;
goto out;