Re: [PATCH RFC v2 00/18] mm/virtio: skip redundant zeroing of host-zeroed reported pages

David Hildenbrand (Arm)
2026-04-21T10:04:59Z

On 4/21/26 04:38, Gregory Price wrote:
> On Mon, Apr 20, 2026 at 07:33:38PM -0400, Michael S. Tsirkin wrote:
>> On Mon, Apr 20, 2026 at 08:20:57PM +0200, David Hildenbrand (Arm) wrote:
>>
>>>
>>> Which would *already* be the case of you use folio_alloc(GFP_ZERO)
>>> instead of magical vma_alloc_folio() + folio_zero_user().
>>>
>>> I don't really see how vma_alloc_folio_hints() -- that also consumes the
>>> address -- is any better in that regard?
>>
>> By itself, it is not. But the issue is propagating the address from
>> there all over mm. If we miss even one place - we get a subtle cache
>> corruption on non x86.
>>
>
> Why does it need to propogate?
>
> Can we leave folio_zero_user() callers the same, but add a PG_zeroed
> check in folio_zero_user() that skips the zeroing (but not the cache
> flush) and clear the PG_zeroed bit?

folio_zero_user() is just an abomination, really.

--
Cheers,

David