On Tue, Jul 12, 2022 at 08:02:34PM +0200, Gupta, Pankaj wrote:
On 7/6/2022 10:20 AM, Chao Peng wrote:
From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com
Implement shmem as a memfile_notifier backing store. Essentially it interacts with the memfile_notifier feature flags for userspace access/page migration/page reclaiming and implements the necessary memfile_backing_store callbacks.
Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Chao Peng chao.p.peng@linux.intel.com
include/linux/shmem_fs.h | 2 + mm/shmem.c | 109 ++++++++++++++++++++++++++++++++++++++- 2 files changed, 110 insertions(+), 1 deletion(-)
...
+#ifdef CONFIG_MIGRATION +static int shmem_migrate_page(struct address_space *mapping,
struct page *newpage, struct page *page,enum migrate_mode mode)+{
- struct inode *inode = mapping->host;
- struct shmem_inode_info *info = SHMEM_I(inode);
- if (info->memfile_node.flags & MEMFILE_F_UNMOVABLE)
return -EOPNOTSUPP;- return migrate_page(mapping, newpage, page, mode);
Wondering how well page migrate would work for private pages on shmem memfd based backend?
From high level: - KVM unset MEMFILE_F_UNMOVABLE bit to indicate it capable of migrating a page. - Introduce new 'migrate' callback(s) to memfile_notifier_ops for KVM to register. - The callback is hooked to migrate_page() here. - Once page migration requested, shmem calls into the 'migrate' callback(s) to perform additional steps for encrypted memory (For TDX we will call TDH.MEM.PAGE.RELOCATE).
Chao
+} +#endif
- const struct address_space_operations shmem_aops = { .writepage = shmem_writepage, .dirty_folio = noop_dirty_folio,
@@ -3814,7 +3872,7 @@ const struct address_space_operations shmem_aops = { .write_end = shmem_write_end, #endif #ifdef CONFIG_MIGRATION
- .migratepage = migrate_page,
- .migratepage = shmem_migrate_page, #endif .error_remove_page = shmem_error_remove_page, };
@@ -3931,6 +3989,51 @@ static struct file_system_type shmem_fs_type = { .fs_flags = FS_USERNS_MOUNT, };