KVM: PPC: Book3S HV: Introduce new capability for 2nd DAWR

Introduce KVM_CAP_PPC_DAWR1 which can be used by QEMU to query whether
KVM supports 2nd DAWR or not. The capability is by default disabled
even when the underlying CPU supports 2nd DAWR. QEMU needs to check
and enable it manually to use the feature.
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

Documentation/virt/kvm/api.rst

@@ -6215,6 +6215,16 @@ the bus lock vm exit can be preempted by a higher priority VM exit, the exit
 notifications to userspace can be KVM_EXIT_BUS_LOCK or other reasons.
 KVM_RUN_BUS_LOCK flag is used to distinguish between them.
 
+7.22 KVM_CAP_PPC_DAWR1
+----------------------
+
+:Architectures: ppc
+:Parameters: none
+:Returns: 0 on success, -EINVAL when CPU doesn't support 2nd DAWR
+
+This capability can be used to check / enable 2nd DAWR feature provided
+by POWER10 processor.
+
 8. Other capabilities.
 ======================
 

arch/powerpc/include/asm/kvm_ppc.h

@@ -314,6 +314,7 @@ struct kvmppc_ops {
 			      int size);
 	int (*enable_svm)(struct kvm *kvm);
 	int (*svm_off)(struct kvm *kvm);
+	int (*enable_dawr1)(struct kvm *kvm);
 };
 
 extern struct kvmppc_ops *kvmppc_hv_ops;

arch/powerpc/kvm/book3s_hv.c

@@ -5642,6 +5642,17 @@ static int kvmhv_svm_off(struct kvm *kvm)
 	return ret;
 }
 
+static int kvmhv_enable_dawr1(struct kvm *kvm)
+{
+	if (!cpu_has_feature(CPU_FTR_DAWR1))
+		return -ENODEV;
+
+	/* kvm == NULL means the caller is testing if the capability exists */
+	if (kvm)
+		kvm->arch.dawr1_enabled = true;
+	return 0;
+}
+
 static struct kvmppc_ops kvm_ops_hv = {
 	.get_sregs = kvm_arch_vcpu_ioctl_get_sregs_hv,
 	.set_sregs = kvm_arch_vcpu_ioctl_set_sregs_hv,
@@ -5685,6 +5696,7 @@ static struct kvmppc_ops kvm_ops_hv = {
 	.store_to_eaddr = kvmhv_store_to_eaddr,
 	.enable_svm = kvmhv_enable_svm,
 	.svm_off = kvmhv_svm_off,
+	.enable_dawr1 = kvmhv_enable_dawr1,
 };
 
 static int kvm_init_subcore_bitmap(void)

arch/powerpc/kvm/powerpc.c

@@ -678,6 +678,10 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = hv_enabled && kvmppc_hv_ops->enable_svm &&
 			!kvmppc_hv_ops->enable_svm(NULL);
 		break;
+	case KVM_CAP_PPC_DAWR1:
+		r = !!(hv_enabled && kvmppc_hv_ops->enable_dawr1 &&
+		       !kvmppc_hv_ops->enable_dawr1(NULL));
+		break;
 #endif
 	default:
 		r = 0;
@@ -2187,6 +2191,12 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 			break;
 		r = kvm->arch.kvm_ops->enable_svm(kvm);
 		break;
+	case KVM_CAP_PPC_DAWR1:
+		r = -EINVAL;
+		if (!is_kvmppc_hv_enabled(kvm) || !kvm->arch.kvm_ops->enable_dawr1)
+			break;
+		r = kvm->arch.kvm_ops->enable_dawr1(kvm);
+		break;
 #endif
 	default:
 		r = -EINVAL;

include/uapi/linux/kvm.h

@@ -1077,6 +1077,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_SYS_HYPERV_CPUID 191
 #define KVM_CAP_DIRTY_LOG_RING 192
 #define KVM_CAP_X86_BUS_LOCK_EXIT 193
+#define KVM_CAP_PPC_DAWR1 194
 
 #ifdef KVM_CAP_IRQ_ROUTING
 

tools/include/uapi/linux/kvm.h

@@ -1056,6 +1056,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_ENFORCE_PV_FEATURE_CPUID 190
 #define KVM_CAP_SYS_HYPERV_CPUID 191
 #define KVM_CAP_DIRTY_LOG_RING 192
+#define KVM_CAP_PPC_DAWR1 194
 
 #ifdef KVM_CAP_IRQ_ROUTING