| Message ID | 20220803155011.43721-13-mlevitsk@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | SMM emulation and interrupt shadow fixes | expand |
On Wed, Aug 03, 2022, Maxim Levitsky wrote: > When the guest CPUID doesn't have support for long mode, 32 bit SMRAM > layout is used and it has no support for preserving EFER and/or SVM > state. > > Note that this isn't relevant to running 32 bit guests on VM which is > long mode capable - such VM can still run 32 bit guests in compatibility > mode. > > Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> > --- > arch/x86/kvm/svm/svm.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 7ca5e06878e19a..64cfd26bc5e7a6 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -4442,6 +4442,15 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram) > if (!is_guest_mode(vcpu)) > return 0; > > + /* > + * 32 bit SMRAM format doesn't preserve EFER and SVM state. > + * SVM should not be enabled by the userspace without marking > + * the CPU as at least long mode capable. Hmm, or userspace can ensure SMIs never get delivered. Maybe? /* * 32-bit SMRAM format doesn't preserve EFER and SVM state. Userspace is * responsible for ensuring nested SVM and SMIs are mutually exclusive. */ > + */ > + Unnecessary newline. > + if (!guest_cpuid_has(vcpu, X86_FEATURE_LM)) > + return 1; This doesn't actually fix anything, RSM will still jump to L2 state but in L1 context. I think we first need to actually handle errors from static_call(kvm_x86_enter_smm). Given that SVM can't even guarantee nested_svm_simple_vmexit() succeeds, i.e. KVM can't force the vCPU out of L2 to ensure triple fault would hit L1, killing the VM seems like the least awful solution (and it's still quite awful). diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 54fa0aa95785..38a6f4089296 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9985,7 +9985,10 @@ static void enter_smm(struct kvm_vcpu *vcpu) * state (e.g. leave guest mode) after we've saved the state into the * SMM state-save area. */ - static_call(kvm_x86_enter_smm)(vcpu, &smram); + if (static_call(kvm_x86_enter_smm)(vcpu, &smram)) { + kvm_vm_dead(vcpu->vm); + return; + } kvm_smm_changed(vcpu, true); kvm_vcpu_write_guest(vcpu, vcpu->arch.smbase + 0xfe00, &smram, sizeof(smram)); > + > smram->smram64.svm_guest_flag = 1; > smram->smram64.svm_guest_vmcb_gpa = svm->nested.vmcb12_gpa; > > -- > 2.26.3 >
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 7ca5e06878e19a..64cfd26bc5e7a6 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4442,6 +4442,15 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram) if (!is_guest_mode(vcpu)) return 0; + /* + * 32 bit SMRAM format doesn't preserve EFER and SVM state. + * SVM should not be enabled by the userspace without marking + * the CPU as at least long mode capable. + */ + + if (!guest_cpuid_has(vcpu, X86_FEATURE_LM)) + return 1; + smram->smram64.svm_guest_flag = 1; smram->smram64.svm_guest_vmcb_gpa = svm->nested.vmcb12_gpa;
When the guest CPUID doesn't have support for long mode, 32 bit SMRAM layout is used and it has no support for preserving EFER and/or SVM state. Note that this isn't relevant to running 32 bit guests on VM which is long mode capable - such VM can still run 32 bit guests in compatibility mode. Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> --- arch/x86/kvm/svm/svm.c | 9 +++++++++ 1 file changed, 9 insertions(+)