[PATCH v4 19/20] kvm: arm/arm64: Expose supported physical address limit for VM

[Suzuki K Poulose <suzuki.poulose@arm.com>]

Advertise the maximum physical address size supported by the host
for a VM as a capability (like max_vcpus and memslots). This could
be used by the userspace to choose the appropriate size for a given
VM.

Cc: Christoffer Dall <cdall@kernel.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
Changes since V3:
 - Switch to a CAP, that can be checkd via EXTENSIONS on KVM device
   fd, rather than a dedicated ioctl.
---
 include/uapi/linux/kvm.h | 1 +
 virt/kvm/arm/arm.c       | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index b6270a3..9a40d82 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -949,6 +949,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_GET_MSR_FEATURES 153
 #define KVM_CAP_HYPERV_EVENTFD 154
 #define KVM_CAP_HYPERV_TLBFLUSH 155
+#define KVM_CAP_ARM_VM_MAX_PHYS_SHIFT 156 /* returns max IPA shift for a VM */
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 135d789..220d886 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -242,6 +242,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		 */
 		r = 1;
 		break;
+	case KVM_CAP_ARM_VM_MAX_PHYS_SHIFT:
+		r = kvm_ipa_limit;
+		break;
 	default:
 		r = kvm_arch_dev_ioctl_check_extension(kvm, ext);
 		break;
-- 
2.7.4