| Message ID | 20180219161444.47050-1-brijesh.singh@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 19/02/2018 17:14, Brijesh Singh wrote: > RSM instruction is used by the SMM handler to return from SMM mode. > Currently, rsm causes a #UD - which results in instruction fetch, decode, > and emulate. By installing the RSM intercept we can avoid the instruction > fetch since we know that #VMEXIT was due to rsm. > > The patch is required for the SEV guest, because in case of SEV guest > memory is encrypted with guest-specific key and hypervisor will not > able to fetch the instruction bytes from the guest memory. > > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: "Radim Krčmář" <rkrcmar@redhat.com> > Cc: Joerg Roedel <joro@8bytes.org> > Cc: Borislav Petkov <bp@suse.de> > Cc: Tom Lendacky <thomas.lendacky@amd.com> > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > --- > arch/x86/kvm/svm.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index 22fc3022386a..20c75e6b74dc 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -300,6 +300,8 @@ module_param(vgif, int, 0444); > static int sev = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT); > module_param(sev, int, 0444); > > +static u8 rsm_ins_bytes[] = "\x0f\xaa"; > + > static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0); > static void svm_flush_tlb(struct kvm_vcpu *vcpu, bool invalidate_gpa); > static void svm_complete_interrupts(struct vcpu_svm *svm); > @@ -1383,6 +1385,7 @@ static void init_vmcb(struct vcpu_svm *svm) > set_intercept(svm, INTERCEPT_SKINIT); > set_intercept(svm, INTERCEPT_WBINVD); > set_intercept(svm, INTERCEPT_XSETBV); > + set_intercept(svm, INTERCEPT_RSM); > > if (!kvm_mwait_in_guest()) { > set_intercept(svm, INTERCEPT_MONITOR); > @@ -3699,6 +3702,12 @@ static int emulate_on_interception(struct vcpu_svm *svm) > return emulate_instruction(&svm->vcpu, 0) == EMULATE_DONE; > } > > +static int rsm_interception(struct vcpu_svm *svm) > +{ > + return x86_emulate_instruction(&svm->vcpu, 0, 0, > + rsm_ins_bytes, 2) == EMULATE_DONE; > +} > + > static int rdpmc_interception(struct vcpu_svm *svm) > { > int err; > @@ -4541,7 +4550,7 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = { > [SVM_EXIT_MWAIT] = mwait_interception, > [SVM_EXIT_XSETBV] = xsetbv_interception, > [SVM_EXIT_NPF] = npf_interception, > - [SVM_EXIT_RSM] = emulate_on_interception, > + [SVM_EXIT_RSM] = rsm_interception, > [SVM_EXIT_AVIC_INCOMPLETE_IPI] = avic_incomplete_ipi_interception, > [SVM_EXIT_AVIC_UNACCELERATED_ACCESS] = avic_unaccelerated_access_interception, > }; > Queued, thanks. Do you need to do the same for SVM_EXIT_INVD? Paolo
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 22fc3022386a..20c75e6b74dc 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -300,6 +300,8 @@ module_param(vgif, int, 0444); static int sev = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT); module_param(sev, int, 0444); +static u8 rsm_ins_bytes[] = "\x0f\xaa"; + static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0); static void svm_flush_tlb(struct kvm_vcpu *vcpu, bool invalidate_gpa); static void svm_complete_interrupts(struct vcpu_svm *svm); @@ -1383,6 +1385,7 @@ static void init_vmcb(struct vcpu_svm *svm) set_intercept(svm, INTERCEPT_SKINIT); set_intercept(svm, INTERCEPT_WBINVD); set_intercept(svm, INTERCEPT_XSETBV); + set_intercept(svm, INTERCEPT_RSM); if (!kvm_mwait_in_guest()) { set_intercept(svm, INTERCEPT_MONITOR); @@ -3699,6 +3702,12 @@ static int emulate_on_interception(struct vcpu_svm *svm) return emulate_instruction(&svm->vcpu, 0) == EMULATE_DONE; } +static int rsm_interception(struct vcpu_svm *svm) +{ + return x86_emulate_instruction(&svm->vcpu, 0, 0, + rsm_ins_bytes, 2) == EMULATE_DONE; +} + static int rdpmc_interception(struct vcpu_svm *svm) { int err; @@ -4541,7 +4550,7 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = { [SVM_EXIT_MWAIT] = mwait_interception, [SVM_EXIT_XSETBV] = xsetbv_interception, [SVM_EXIT_NPF] = npf_interception, - [SVM_EXIT_RSM] = emulate_on_interception, + [SVM_EXIT_RSM] = rsm_interception, [SVM_EXIT_AVIC_INCOMPLETE_IPI] = avic_incomplete_ipi_interception, [SVM_EXIT_AVIC_UNACCELERATED_ACCESS] = avic_unaccelerated_access_interception, };
RSM instruction is used by the SMM handler to return from SMM mode. Currently, rsm causes a #UD - which results in instruction fetch, decode, and emulate. By installing the RSM intercept we can avoid the instruction fetch since we know that #VMEXIT was due to rsm. The patch is required for the SEV guest, because in case of SEV guest memory is encrypted with guest-specific key and hypervisor will not able to fetch the instruction bytes from the guest memory. Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: "Radim Krčmář" <rkrcmar@redhat.com> Cc: Joerg Roedel <joro@8bytes.org> Cc: Borislav Petkov <bp@suse.de> Cc: Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> --- arch/x86/kvm/svm.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)