On 11.02.25 13:11, Fuad Tabba wrote:
Before transitioning a guest_memfd folio to unshared, thereby
disallowing access by the host and allowing the hypervisor to
transition its view of the guest page as private, we need to be
sure that the host doesn't have any references to the folio.
This patch introduces a new type for guest_memfd folios, which
isn't activated in this series but is here as a placeholder and
to facilitate the code in the next patch. This will be used in
the future to register a callback that informs the guest_memfd
subsystem when the last reference is dropped, therefore knowing
that the host doesn't have any remaining references.
Signed-off-by: Fuad Tabba <tabba@xxxxxxxxxx>
---
[...]
static const char *page_type_name(unsigned int page_type)
diff --git a/mm/swap.c b/mm/swap.c
index 47bc1bb919cc..241880a46358 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -38,6 +38,10 @@
#include <linux/local_lock.h>
#include <linux/buffer_head.h>
+#ifdef CONFIG_KVM_GMEM_SHARED_MEM
+#include <linux/kvm_host.h>
+#endif
+
#include "internal.h"
#define CREATE_TRACE_POINTS
@@ -101,6 +105,11 @@ static void free_typed_folio(struct folio *folio)
case PGTY_hugetlb:
free_huge_folio(folio);
return;
+#endif
+#ifdef CONFIG_KVM_GMEM_SHARED_MEM
+ case PGTY_guestmem:
+ kvm_gmem_handle_folio_put(folio);
+ return;
Hm, if KVM is built as a module, will that work? Or would we need the
core-mm guest_memfd shim that would always be compiled into the core and
decouple KVM from guest_memfd ("library")?
--
Cheers,
David / dhildenb
