Re: [PATCH, RFC 13/62] x86/mm: Add hooks to allocate and free encrypted pages

[Peter Zijlstra]

On Fri, Jun 14, 2019 at 11:34:09AM +0200, Peter Zijlstra wrote:
> On Wed, May 08, 2019 at 05:43:33PM +0300, Kirill A. Shutemov wrote:
> 
> > +		lookup_page_ext(page)->keyid = keyid;

> > +		lookup_page_ext(page)->keyid = 0;

Also, perhaps paranoid; but do we want something like:

static inline void page_set_keyid(struct page *page, int keyid)
{
	/* ensure nothing creeps after changing the keyid */
	barrier();
	WRITE_ONCE(lookup_page_ext(page)->keyid, keyid);
	barrier();
	/* ensure nothing creeps before changing the keyid */
}

And this is very much assuming there is no concurrency through the
allocator locks.