When guest_memfd becomes a library, a callback will need to be made to the owner (KVM SEV) to transition pages back to hypervisor-owned/shared state. This is currently being done as part of .free_folio() address space op, but this callback shouldn't assume that the mapping still exists. guest_memfd library will need the mapping to still exist to look up its operations table. .release_folio() and .invalidate_folio() address space ops can serve the same purpose here. The key difference between release_folio() and free_folio() is whether the mapping is still valid at time of the callback. This approach was discussed in the link in the footer, but not taken because free_folio() was easier to implement. Link: https://lore.kernel.org/kvm/20231016115028.996656-1-michael.roth@xxxxxxx/ Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx> --- virt/kvm/guest_memfd.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 47a9f68f7b247f4cba0c958b4c7cd9458e7c46b4..13f83ad8a4c26ba82aca4f2684f22044abb4bc19 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -358,22 +358,35 @@ static int kvm_gmem_error_folio(struct address_space *mapping, struct folio *fol } #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE -static void kvm_gmem_free_folio(struct folio *folio) +static bool kvm_gmem_release_folio(struct folio *folio, gfp_t gfp) { struct page *page = folio_page(folio, 0); kvm_pfn_t pfn = page_to_pfn(page); int order = folio_order(folio); kvm_arch_gmem_invalidate(pfn, pfn + (1ul << order)); + + return true; +} + +static void kvm_gmem_invalidate_folio(struct folio *folio, size_t offset, + size_t len) +{ + WARN_ON_ONCE(offset != 0); + WARN_ON_ONCE(len != folio_size(folio)); + + if (offset == 0 && len == folio_size(folio)) + filemap_release_folio(folio, 0); } #endif static const struct address_space_operations kvm_gmem_aops = { .dirty_folio = noop_dirty_folio, - .migrate_folio = kvm_gmem_migrate_folio, + .migrate_folio = kvm_gmem_migrate_folio, .error_remove_folio = kvm_gmem_error_folio, #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE - .free_folio = kvm_gmem_free_folio, + .release_folio = kvm_gmem_release_folio, + .invalidate_folio = kvm_gmem_invalidate_folio, #endif }; -- 2.34.1
