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KVM: nSVM: Implement support for nested VNMI 

Allow L1 to use vNMI to accelerate its injection of NMI to L2 by
propagating vNMI int_ctl bits from/to vmcb12 to/from vmcb02.

To handle both the case where vNMI is enabled for L1 and L2, and where
vNMI is enabled for L1 but _not_ L2, move pending L1 vNMIs to nmi_pending
on nested VM-Entry and raise KVM_REQ_EVENT, i.e. rely on existing code to
route the NMI to the correct domain.

On nested VM-Exit, reverse the process and set/clear V_NMI_PENDING for L1
based one whether nmi_pending is zero or non-zero.  There is no need to
consider vmcb02 in this case, as V_NMI_PENDING can be set in vmcb02 if
vNMI is disabled for L2, and if vNMI is enabled for L2, then L1 and L2
have different NMI contexts.

Co-developed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Santosh Shukla <santosh.shukla@amd.com>
Link: https://lore.kernel.org/r/20230227084016.3368-12-santosh.shukla@amd.com
[sean: massage changelog to match the code]
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Santosh Shukla 2023-02-27 14:10:16 +05:30 committed by Sean Christopherson
parent fa4c027a79
commit 0977cfac6e
3 changed files with 45 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
arch/x86/kvm/svm/nested.c
View File

@ -281,6 +281,11 @@ static bool __nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
if (CC(!nested_svm_check_tlb_ctl(vcpu, control->tlb_ctl)))
return false;
if (CC((control->int_ctl & V_NMI_ENABLE_MASK) &&
!vmcb12_is_intercept(control, INTERCEPT_NMI))) {
return false;
}
return true;
}
@ -436,6 +441,9 @@ void nested_sync_control_from_vmcb02(struct vcpu_svm *svm)
if (nested_vgif_enabled(svm))
mask |= V_GIF_MASK;
if (nested_vnmi_enabled(svm))
mask |= V_NMI_BLOCKING_MASK | V_NMI_PENDING_MASK;
svm->nested.ctl.int_ctl &= ~mask;
svm->nested.ctl.int_ctl |= svm->vmcb->control.int_ctl & mask;
}
@ -655,6 +663,17 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm,
else
int_ctl_vmcb01_bits |= (V_GIF_MASK | V_GIF_ENABLE_MASK);
if (vnmi) {
if (vmcb01->control.int_ctl & V_NMI_PENDING_MASK) {
svm->vcpu.arch.nmi_pending++;
kvm_make_request(KVM_REQ_EVENT, &svm->vcpu);
}
if (nested_vnmi_enabled(svm))
int_ctl_vmcb12_bits |= (V_NMI_PENDING_MASK |
V_NMI_ENABLE_MASK |
V_NMI_BLOCKING_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;
@ -1055,6 +1074,20 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
svm_update_lbrv(vcpu);
}
if (vnmi) {
if (vmcb02->control.int_ctl & V_NMI_BLOCKING_MASK)
vmcb01->control.int_ctl |= V_NMI_BLOCKING_MASK;
else
vmcb01->control.int_ctl &= ~V_NMI_BLOCKING_MASK;
if (vcpu->arch.nmi_pending) {
vcpu->arch.nmi_pending--;
vmcb01->control.int_ctl |= V_NMI_PENDING_MASK;
} else {
vmcb01->control.int_ctl &= ~V_NMI_PENDING_MASK;
}
}
/*
* On vmexit the GIF is set to false and
* no event can be injected in L1.

5
arch/x86/kvm/svm/svm.c
View File

@ -4246,6 +4246,8 @@ 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_VNMI);
svm_recalc_instruction_intercepts(vcpu, svm);
/* For sev guests, the memory encryption bit is not reserved in CR3. */
@ -5001,6 +5003,9 @@ 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_VNMI);
/* Nested VM can receive #VMEXIT instead of triggering #GP */
kvm_cpu_cap_set(X86_FEATURE_SVME_ADDR_CHK);
}

7
arch/x86/kvm/svm/svm.h
View File

@ -266,6 +266,7 @@ 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;
@ -540,6 +541,12 @@ static inline bool nested_npt_enabled(struct vcpu_svm *svm)
return svm->nested.ctl.nested_ctl & SVM_NESTED_CTL_NP_ENABLE;
}
static inline bool nested_vnmi_enabled(struct vcpu_svm *svm)
{
return svm->vnmi_enabled &&
(svm->nested.ctl.int_ctl & V_NMI_ENABLE_MASK);
}
static inline bool is_x2apic_msrpm_offset(u32 offset)
{
/* 4 msrs per u8, and 4 u8 in u32 */