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Subject[PATCHv4 6/8] KVM: nSVM: implement nested VNMI
Date
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>
---
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 76dcc8a3e849..3d986ec83147 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -662,6 +662,11 @@ 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;
@@ -1010,6 +1015,28 @@ 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 4aa7606a9aa2..2e50a7ab32db 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4217,6 +4217,8 @@ 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_V_NMI);
+
svm_recalc_instruction_intercepts(vcpu, svm);

/* For sev guests, the memory encryption bit is not reserved in CR3. */
@@ -4967,6 +4969,9 @@ 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_V_NMI);
+
/* 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
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