[PATCH v6 05/10] KVM: guest_memfd: Handle in-place shared memory as guest_memfd backed memory

Fuad Tabba
2025-03-12T17:58:42Z

For VMs that allow sharing guest_memfd backed memory in-place,
handle that memory the same as "private" guest_memfd memory. This
means that faulting that memory in the host or in the guest will
go through the guest_memfd subsystem.

Note that the word "private" in the name of the function
kvm_mem_is_private() doesn't necessarily indicate that the memory
isn't shared, but is due to the history and evolution of
guest_memfd and the various names it has received. In effect,
this function is used to multiplex between the path of a normal
page fault and the path of a guest_memfd backed page fault.

Signed-off-by: Fuad Tabba <tabba@google.com>
---
include/linux/kvm_host.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 601bbcaa5e41..3d5595a71a2a 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2521,7 +2521,8 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
#else
static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
{
- return false;
+ return kvm_arch_gmem_supports_shared_mem(kvm) &&
+ kvm_slot_can_be_private(gfn_to_memslot(kvm, gfn));
}
#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */

--
2.49.0.rc0.332.g42c0ae87b1-goog