svm: Introduce AMD IOMMU avic_ga_log_notifier

This patch introduces avic_ga_log_notifier, which will be called
by IOMMU driver whenever it handles the Guest vAPIC (GA) log entry.

Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -785,6 +785,7 @@ struct kvm_arch {
 	u32 ldr_mode;
 	struct page *avic_logical_id_table_page;
 	struct page *avic_physical_id_table_page;
+	struct hlist_node hnode;
 
 	bool x2apic_format;
 	bool x2apic_broadcast_quirk_disabled;

arch/x86/kvm/svm.c

@@ -34,6 +34,8 @@
 #include <linux/sched.h>
 #include <linux/trace_events.h>
 #include <linux/slab.h>
+#include <linux/amd-iommu.h>
+#include <linux/hashtable.h>
 
 #include <asm/apic.h>
 #include <asm/perf_event.h>
@@ -945,6 +947,55 @@ static void svm_disable_lbrv(struct vcpu_svm *svm)
 	set_msr_interception(msrpm, MSR_IA32_LASTINTTOIP, 0, 0);
 }
 
+/* Note:
+ * This hash table is used to map VM_ID to a struct kvm_arch,
+ * when handling AMD IOMMU GALOG notification to schedule in
+ * a particular vCPU.
+ */
+#define SVM_VM_DATA_HASH_BITS	8
+DECLARE_HASHTABLE(svm_vm_data_hash, SVM_VM_DATA_HASH_BITS);
+static spinlock_t svm_vm_data_hash_lock;
+
+/* Note:
+ * This function is called from IOMMU driver to notify
+ * SVM to schedule in a particular vCPU of a particular VM.
+ */
+static int avic_ga_log_notifier(u32 ga_tag)
+{
+	unsigned long flags;
+	struct kvm_arch *ka = NULL;
+	struct kvm_vcpu *vcpu = NULL;
+	u32 vm_id = AVIC_GATAG_TO_VMID(ga_tag);
+	u32 vcpu_id = AVIC_GATAG_TO_VCPUID(ga_tag);
+
+	pr_debug("SVM: %s: vm_id=%#x, vcpu_id=%#x\n", __func__, vm_id, vcpu_id);
+
+	spin_lock_irqsave(&svm_vm_data_hash_lock, flags);
+	hash_for_each_possible(svm_vm_data_hash, ka, hnode, vm_id) {
+		struct kvm *kvm = container_of(ka, struct kvm, arch);
+		struct kvm_arch *vm_data = &kvm->arch;
+
+		if (vm_data->avic_vm_id != vm_id)
+			continue;
+		vcpu = kvm_get_vcpu_by_id(kvm, vcpu_id);
+		break;
+	}
+	spin_unlock_irqrestore(&svm_vm_data_hash_lock, flags);
+
+	if (!vcpu)
+		return 0;
+
+	/* Note:
+	 * At this point, the IOMMU should have already set the pending
+	 * bit in the vAPIC backing page. So, we just need to schedule
+	 * in the vcpu.
+	 */
+	if (vcpu->mode == OUTSIDE_GUEST_MODE)
+		kvm_vcpu_wake_up(vcpu);
+
+	return 0;
+}
+
 static __init int svm_hardware_setup(void)
 {
 	int cpu;
@@ -1003,10 +1054,15 @@ static __init int svm_hardware_setup(void)
 	if (avic) {
 		if (!npt_enabled ||
 		    !boot_cpu_has(X86_FEATURE_AVIC) ||
-		    !IS_ENABLED(CONFIG_X86_LOCAL_APIC))
+		    !IS_ENABLED(CONFIG_X86_LOCAL_APIC)) {
 			avic = false;
-		else
+		} else {
 			pr_info("AVIC enabled\n");
+
+			hash_init(svm_vm_data_hash);
+			spin_lock_init(&svm_vm_data_hash_lock);
+			amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
+		}
 	}
 
 	return 0;
@@ -1327,6 +1383,7 @@ static inline int avic_free_vm_id(int id)
 
 static void avic_vm_destroy(struct kvm *kvm)
 {
+	unsigned long flags;
 	struct kvm_arch *vm_data = &kvm->arch;
 
 	avic_free_vm_id(vm_data->avic_vm_id);
@@ -1335,10 +1392,15 @@ static void avic_vm_destroy(struct kvm *kvm)
 		__free_page(vm_data->avic_logical_id_table_page);
 	if (vm_data->avic_physical_id_table_page)
 		__free_page(vm_data->avic_physical_id_table_page);
+
+	spin_lock_irqsave(&svm_vm_data_hash_lock, flags);
+	hash_del(&vm_data->hnode);
+	spin_unlock_irqrestore(&svm_vm_data_hash_lock, flags);
 }
 
 static int avic_vm_init(struct kvm *kvm)
 {
+	unsigned long flags;
 	int err = -ENOMEM;
 	struct kvm_arch *vm_data = &kvm->arch;
 	struct page *p_page;
@@ -1367,6 +1429,10 @@ static int avic_vm_init(struct kvm *kvm)
 	vm_data->avic_logical_id_table_page = l_page;
 	clear_page(page_address(l_page));
 
+	spin_lock_irqsave(&svm_vm_data_hash_lock, flags);
+	hash_add(svm_vm_data_hash, &vm_data->hnode, vm_data->avic_vm_id);
+	spin_unlock_irqrestore(&svm_vm_data_hash_lock, flags);
+
 	return 0;
 
 free_avic: