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

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Date:   Thu, 27 Oct 2022 14:08:29 +0530
From:   Santosh Shukla <santosh.shukla@....com>
To:     <pbonzini@...hat.com>, <seanjc@...gle.com>
CC:     <kvm@...r.kernel.org>, <jmattson@...gle.com>, <joro@...tes.org>,
        <linux-kernel@...r.kernel.org>, <mail@...iej.szmigiero.name>,
        <mlevitsk@...hat.com>, <thomas.lendacky@....com>,
        <vkuznets@...hat.com>
Subject: [PATCHv5 6/8] KVM: nSVM: implement nested VNMI

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@....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