Messages in this thread | | | From | "Michael Kelley (LINUX)" <> | Subject | RE: [PATCHv3 0/3] x86/tdx: Fix one more load_unaligned_zeropad() issue | Date | Mon, 10 Jul 2023 14:17:28 +0000 |
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From: Tom Lendacky <thomas.lendacky@amd.com> Sent: Monday, July 10, 2023 6:59 AM > > 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@shutemov.name> 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@linux.intel.com> 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... >
Yes, I'm still pursuing the RFC patch. In addition to solving the SNP problems, I think there are some benefits with TDX. But I need to have further discussion with Kirill, which may be delayed a bit while he's out on vacation.
Michael
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