Re: [PATCH v7 04/14] mm/shmem: Support memfile_notifier

[Gupta, Pankaj]

> > > > > +#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).
> >
> > Yes, that would require additional (protocol specific) handling for private
> > pages. Was trying to find where "MEMFILE_F_UNMOVABLE" flag is set currently?
>
> It's set with memfile_register_notifier() in patch 13.

o.k.

Thanks,

Pankaj