[PATCH] KVM: x86: Add host physical address width capability

[Bandan Das]

Let userspace inquire the maximum physical address width
of the host processors; this can be used to identify maximum
memory that can be assigned to the guest.

Reported-by: Laszlo Ersek <lersek@xxxxxxxxxx>
Signed-off-by: Bandan Das <bsd@xxxxxxxxxx>
---
 arch/x86/kvm/x86.c       | 3 +++
 include/uapi/linux/kvm.h | 1 +
 2 files changed, 4 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bbaf44e..97d6746 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2683,6 +2683,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_NR_MEMSLOTS:
 		r = KVM_USER_MEM_SLOTS;
 		break;
+	case KVM_CAP_PHY_ADDR_WIDTH:
+		r = boot_cpu_data.x86_phys_bits;
+		break;
 	case KVM_CAP_PV_MMU:	/* obsolete */
 		r = 0;
 		break;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 716ad4a..e7949a1 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -817,6 +817,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_DISABLE_QUIRKS 116
 #define KVM_CAP_X86_SMM 117
 #define KVM_CAP_MULTI_ADDRESS_SPACE 118
+#define KVM_CAP_PHY_ADDR_WIDTH 119
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.4.3

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