[PATCHv5 6/8] KVM: nSVM: implement nested VNMI

Santosh Shukla
2022-10-27T08:43:20Z

In order to support nested VNMI requires saving and restoring the VNMI
bits during nested entry and exit.
In case of L1 and L2 both using VNMI- Copy VNMI bits from vmcb12 to
vmcb02 during entry and vice-versa during exit.
And in case of L1 uses VNMI and L2 doesn't- Copy VNMI bits from vmcb01 to
vmcb02 during entry and vice-versa during exit.

Tested with the KVM-unit-test and Nested Guest scenario.

Signed-off-by: Santosh Shukla <santosh.shukla@amd.com>
---
v5:
- Renamed s/X86_FEATURE_V_NMI/X86_FEATURE_AMD_VNMI
v3:
- Added code to save and restore VNMI bit for L1 using vnmi and L2
doesn't for the entry and exit case.

v2:
- Save the V_NMI_PENDING/MASK state in vmcb12 on vmexit.
- Tested nested environment - L1 injecting vnmi to L2.
- Tested vnmi in kvm-unit-test.

arch/x86/kvm/svm/nested.c | 27 +++++++++++++++++++++++++++
arch/x86/kvm/svm/svm.c | 5 +++++
arch/x86/kvm/svm/svm.h | 6 ++++++
3 files changed, 38 insertions(+)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 4c620999d230..d1c22c89427e 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -640,6 +640,11 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm,
else
int_ctl_vmcb01_bits |= (V_GIF_MASK | V_GIF_ENABLE_MASK);

+ if (nested_vnmi_enabled(svm))
+ int_ctl_vmcb12_bits |= (V_NMI_PENDING | V_NMI_ENABLE | V_NMI_MASK);
+ else
+ int_ctl_vmcb01_bits |= (V_NMI_PENDING | V_NMI_ENABLE | V_NMI_MASK);
+
/* Copied from vmcb01. msrpm_base can be overwritten later. */
vmcb02->control.nested_ctl = vmcb01->control.nested_ctl;
vmcb02->control.iopm_base_pa = vmcb01->control.iopm_base_pa;
@@ -992,6 +997,28 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
vmcb12->control.event_inj = svm->nested.ctl.event_inj;
vmcb12->control.event_inj_err = svm->nested.ctl.event_inj_err;

+ if (nested_vnmi_enabled(svm)) {
+ if (vmcb02->control.int_ctl & V_NMI_MASK)
+ vmcb12->control.int_ctl |= V_NMI_MASK;
+ else
+ vmcb12->control.int_ctl &= ~V_NMI_MASK;
+
+ if (vmcb02->control.int_ctl & V_NMI_PENDING)
+ vmcb12->control.int_ctl |= V_NMI_PENDING;
+ else
+ vmcb12->control.int_ctl &= ~V_NMI_PENDING;
+ } else {
+ if (vmcb02->control.int_ctl & V_NMI_MASK)
+ vmcb01->control.int_ctl |= V_NMI_MASK;
+ else
+ vmcb01->control.int_ctl &= ~V_NMI_MASK;
+
+ if (vmcb02->control.int_ctl & V_NMI_PENDING)
+ vmcb01->control.int_ctl |= V_NMI_PENDING;
+ else
+ vmcb01->control.int_ctl &= ~V_NMI_PENDING;
+ }
+
if (!kvm_pause_in_guest(vcpu->kvm)) {
vmcb01->control.pause_filter_count = vmcb02->control.pause_filter_count;
vmcb_mark_dirty(vmcb01, VMCB_INTERCEPTS);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index cf05a41779f3..d8edd40e48e1 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4216,6 +4216,8 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)

svm->vgif_enabled = vgif && guest_cpuid_has(vcpu, X86_FEATURE_VGIF);

+ svm->vnmi_enabled = vnmi && guest_cpuid_has(vcpu, X86_FEATURE_AMD_VNMI);
+
svm_recalc_instruction_intercepts(vcpu, svm);

/* For sev guests, the memory encryption bit is not reserved in CR3. */
@@ -4958,6 +4960,9 @@ static __init void svm_set_cpu_caps(void)
if (vgif)
kvm_cpu_cap_set(X86_FEATURE_VGIF);

+ if (vnmi)
+ kvm_cpu_cap_set(X86_FEATURE_AMD_VNMI);
+
/* Nested VM can receive #VMEXIT instead of triggering #GP */
kvm_cpu_cap_set(X86_FEATURE_SVME_ADDR_CHK);
}
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 7857a89d0ec8..4d6245ef5b6c 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -253,6 +253,7 @@ struct vcpu_svm {
bool pause_filter_enabled : 1;
bool pause_threshold_enabled : 1;
bool vgif_enabled : 1;
+ bool vnmi_enabled : 1;

u32 ldr_reg;
u32 dfr_reg;
@@ -533,6 +534,11 @@ static inline bool is_x2apic_msrpm_offset(u32 offset)
(msr < (APIC_BASE_MSR + 0x100));
}

+static inline bool nested_vnmi_enabled(struct vcpu_svm *svm)
+{
+ return svm->vnmi_enabled && (svm->nested.ctl.int_ctl & V_NMI_ENABLE);
+}
+
static inline struct vmcb *get_vnmi_vmcb(struct vcpu_svm *svm)
{
if (!vnmi)
--
2.25.1