[RFC PATCH v1 3/9] KVM: guest_memfd: Add KVM capability to check if guest_memfd is host mappable

Fuad Tabba
2025-01-22T15:27:54Z

Add the KVM capability KVM_CAP_GUEST_MEMFD_MAPPABLE, which is
true if mapping guest memory is supported by the host.

Signed-off-by: Fuad Tabba <tabba@google.com>
---
include/uapi/linux/kvm.h | 1 +
virt/kvm/kvm_main.c | 4 ++++
2 files changed, 5 insertions(+)

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 502ea63b5d2e..021f8ef9979b 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -933,6 +933,7 @@ struct kvm_enable_cap {
#define KVM_CAP_PRE_FAULT_MEMORY 236
#define KVM_CAP_X86_APIC_BUS_CYCLES_NS 237
#define KVM_CAP_X86_GUEST_MODE 238
+#define KVM_CAP_GUEST_MEMFD_MAPPABLE 239

struct kvm_irq_routing_irqchip {
__u32 irqchip;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ad9802012a3f..9cd6690b7955 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4872,6 +4872,10 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
#ifdef CONFIG_KVM_PRIVATE_MEM
case KVM_CAP_GUEST_MEMFD:
return !kvm || kvm_arch_has_private_mem(kvm);
+#endif
+#ifdef CONFIG_KVM_GMEM_MAPPABLE
+ case KVM_CAP_GUEST_MEMFD_MAPPABLE:
+ return !kvm || kvm_arch_private_mem_inplace(kvm);
#endif
default:
break;
--
2.48.0.rc2.279.g1de40edade-goog