[RFC PATCH v2 18/28] KVM: arm64: Introduce KVM_CAP_ARM_ID_REG_WRITABLE capability

[Reiji Watanabe]

Introduce a new capability KVM_CAP_ARM_ID_REG_WRITABLE to indicate
that ID registers are writable by userspace.

Signed-off-by: Reiji Watanabe <reijiw at google.com>
---
 Documentation/virt/kvm/api.rst | 8 ++++++++
 arch/arm64/kvm/arm.c           | 1 +
 include/uapi/linux/kvm.h       | 1 +
 3 files changed, 10 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index a6729c8cf063..f7dfb5127310 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -7265,3 +7265,11 @@ The argument to KVM_ENABLE_CAP is also a bitmask, and must be a subset
 of the result of KVM_CHECK_EXTENSION.  KVM will forward to userspace
 the hypercalls whose corresponding bit is in the argument, and return
 ENOSYS for the others.
+
+8.35 KVM_CAP_ARM_ID_REG_WRITABLE
+--------------------------------
+
+:Architectures: arm64
+
+This capability indicates that userspace can modify the ID registers
+via KVM_SET_ONE_REG ioctl.
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 528058920b64..87b8432f5719 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -197,6 +197,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_SET_GUEST_DEBUG:
 	case KVM_CAP_VCPU_ATTRIBUTES:
 	case KVM_CAP_PTP_KVM:
+	case KVM_CAP_ARM_ID_REG_WRITABLE:
 		r = 1;
 		break;
 	case KVM_CAP_SET_GUEST_DEBUG2:
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index a067410ebea5..3345a57f05a6 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1112,6 +1112,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_BINARY_STATS_FD 203
 #define KVM_CAP_EXIT_ON_EMULATION_FAILURE 204
 #define KVM_CAP_ARM_MTE 205
+#define KVM_CAP_ARM_ID_REG_WRITABLE 206
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.33.1.1089.g2158813163f-goog