Re: [PATCHv3 0/3] x86/tdx: Fix one more load_unaligned_zeropad() issue

[Tom Lendacky]

On 7/9/23 01:09, Kirill A. Shutemov wrote:
> On Sat, Jul 08, 2023 at 11:53:08PM +0000, Michael Kelley (LINUX) wrote:
> > From: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> Sent: Friday, July 7, 2023 7:07 AM
> > > On Thu, Jul 06, 2023 at 04:48:32PM +0000, Michael Kelley (LINUX) wrote:
> > > > From: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Sent: Tuesday, June 6, 2023 2:56 AM
> >
> > [snip]
> >
> > > It only addresses the problem that happens on transition, but
> > > load_unaligned_zeropad() is still a problem for the shared mappings in
> > > general, after transition is complete. Like if load_unaligned_zeropad()
> > > steps from private to shared mapping and shared mapping triggers #VE,
> > > kernel should be able to handle it.
> >
> > I'm showing my ignorance of TDX architectural details, but what's the
> > situation where shared mappings in general can trigger a #VE?  How
> > do such situations get handled for references that aren't from
> > load_unaligned_zeropad()?
>
> Shared mappings are under host/VMM control. It can just not map the page
> in shared-ept and trigger ept-violation #VE.
>
> > > Any comments?
> >
> > This looks good to me.  I applied the diff to a TDX VM running on
> > Hyper-V.  When a  load_unaligned_zeropad() occurs on a page that is
> > transitioning between private and shared, the zeropad fixup is now
> > done correctly via the #VE handler.  (This is *without* my RFC patch to
> > mark the pages invalid during a transition.)
>
> Great.
>
> I am at vacation for the next two weeks. I will prepare a proper patch
> when I am back. Feel free to make patch yourself if you feel it is urgent.

Michael,

Are you still pursuing the RFC patch, then? Just trying to decide whether 
a patch will be needed for SNP...

Thanks,
Tom