On 14/12/24 03:48, Fuad Tabba wrote:
Add support for mmap() and fault() for guest_memfd in the host. The ability to fault in a guest page is contingent on that page being shared with the host. The guest_memfd PRIVATE memory attribute is not used for two reasons. First because it reflects the userspace expectation for that memory location, and therefore can be toggled by userspace. The second is, although each guest_memfd file has a 1:1 binding with a KVM instance, the plan is to allow multiple files per inode, e.g. to allow intra-host migration to a new KVM instance, without destroying guest_memfd. The mapping is restricted to only memory explicitly shared with the host. KVM checks that the host doesn't have any mappings for private memory via the folio's refcount. To avoid races between paths that check mappability and paths that check whether the host has any mappings (via the refcount), the folio lock is held in while either check is being performed. This new feature is gated with a new configuration option, CONFIG_KVM_GMEM_MAPPABLE. Co-developed-by: Ackerley Tng <ackerleytng@xxxxxxxxxx> Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx> Co-developed-by: Elliot Berman <quic_eberman@xxxxxxxxxxx> Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx> Signed-off-by: Fuad Tabba <tabba@xxxxxxxxxx> --- The functions kvm_gmem_is_mapped(), kvm_gmem_set_mappable(), and int kvm_gmem_clear_mappable() are not used in this patch series. They are intended to be used in future patches [*], which check and toggle mapability when the guest shares/unshares pages with the host. [*] https://android-kvm.googlesource.com/linux/+/refs/heads/tabba/guestmem-6.13-v4-pkvm
This one requires access, can you please push it somewhere public? I am interested in in-place shared<->private memory conversion and I wonder if kvm_gmem_set_mappable() that guy. Thanks,
-- Alexey
