Messages in this thread | | | Date | Wed, 13 Jul 2022 15:44:58 +0800 | From | Chao Peng <> | Subject | Re: [PATCH v7 04/14] mm/shmem: Support memfile_notifier |
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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, > > };
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