KVM: X86: Run higher VMPL if events are pending

Each vCPU VMPL maintains its own set of pending events. When a vCPU is kicked or exits back to the host, check using an X86 op to see if events are pending for a higher priority VMPL and allow switching to that VMPL. This has been implemented for SEV-SNP where VMPL0 is checked when running a lower VMPL and the current_vmpl is switched to VMPL0 if there are pending events. Signed-off-by: Roy Hopkins <[email protected]>
coconut-svsm · Oct 8, 2024 · 5c78db7 · 5c78db7
1 parent d39aa91
commit 5c78db7
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Showing 6 changed files with 37 additions and 2 deletions.
diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
@@ -140,6 +140,7 @@ KVM_X86_OP_OPTIONAL(alloc_apic_backing_page)
 KVM_X86_OP_OPTIONAL_RET0(gmem_prepare)
 KVM_X86_OP_OPTIONAL_RET0(private_max_mapping_level)
 KVM_X86_OP_OPTIONAL(gmem_invalidate)
+KVM_X86_OP_OPTIONAL_RET0(pending_event_higher_vmpl)
 
 #undef KVM_X86_OP
 #undef KVM_X86_OP_OPTIONAL

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
@@ -1839,6 +1839,7 @@ struct kvm_x86_ops {
 	int (*gmem_prepare)(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order);
 	void (*gmem_invalidate)(kvm_pfn_t start, kvm_pfn_t end);
 	int (*private_max_mapping_level)(struct kvm *kvm, kvm_pfn_t pfn);
+	int (*pending_event_higher_vmpl)(struct kvm_vcpu *vcpu);
 };
 
 struct kvm_x86_nested_ops {

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
@@ -5574,3 +5574,20 @@ bool sev_snp_blocked(enum inject_type type, struct kvm_vcpu *vcpu)
 
 	return blocked;
 }
+
+int sev_pending_event_higher_vmpl(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_vmpl_state *vcpu_parent = vcpu->vcpu_parent;
+
+	/*
+	 * Check to see if VMPL0 has any pending events to process
+	 * if the current VMPL is lower
+	 */
+	if (vcpu->vmpl > 0) {
+		if (kvm_test_request(KVM_REQ_EVENT, vcpu_parent->vcpu_vmpl[0])) {
+			vcpu_parent->target_vmpl = 0;
+			return 1;
+		}
+	}
+	return 0;
+}
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
@@ -5172,6 +5172,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
 
 	.vm_copy_enc_context_from = sev_vm_copy_enc_context_from,
 	.vm_move_enc_context_from = sev_vm_move_enc_context_from,
+	.pending_event_higher_vmpl = sev_pending_event_higher_vmpl,
 #endif
 	.check_emulate_instruction = svm_check_emulate_instruction,
 

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
@@ -800,6 +800,7 @@ static inline bool sev_snp_is_rinj_active(struct kvm_vcpu *vcpu)
 	return sev_snp_guest(vcpu->kvm) &&
 		(sev->vmsa_features[vcpu->vmpl] & SVM_SEV_FEAT_RESTRICTED_INJECTION);
 };
+int sev_pending_event_higher_vmpl(struct kvm_vcpu *vcpu);
 #else
 static inline struct page *snp_safe_alloc_page_node(int node, gfp_t gfp)
 {

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
@@ -11310,6 +11310,7 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
 {
 	int r;
 	struct kvm_vcpu_vmpl_state *vcpu_parent = vcpu->vcpu_parent;
+	int vmpl;
 
 	vcpu->common->run->exit_reason = KVM_EXIT_UNKNOWN;
 
@@ -11334,8 +11335,15 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
 		if (kvm_xen_has_pending_events(vcpu))
 			kvm_xen_inject_pending_events(vcpu);
 
-		if (kvm_cpu_has_pending_timer(vcpu))
-			kvm_inject_pending_timer_irqs(vcpu);
+		/*
+		 * Check for pending timer interrupts on all vCPU priorties. We
+		 * will switch to the higher priority VMPL if a pending interrupt
+		 * is ready.
+		 */
+		for (vmpl = 0; vmpl <= vcpu_parent->max_vmpl; ++vmpl) {
+			if (kvm_cpu_has_pending_timer(vcpu_parent->vcpu_vmpl[vmpl]))
+				kvm_inject_pending_timer_irqs(vcpu_parent->vcpu_vmpl[vmpl]);
+		}
 
 		if (dm_request_for_irq_injection(vcpu) &&
 			kvm_vcpu_ready_for_interrupt_injection(vcpu)) {
@@ -11356,6 +11364,12 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
 		/* If the exit code results in a VTL switch then let the caller handle it */
 		if (vcpu_parent->target_vmpl != vcpu_parent->current_vmpl)
 			break;
+
+		/* Exit on pending interrupts/events for a higher priority VMPL */
+		if (kvm_x86_call(pending_event_higher_vmpl)(vcpu)) {
+			r = 0;
+			break;
+		}
 	}
 
 	return r;