Re: [PATCH v2 0/5] x86/mm/pat: CPA fixes

[Atish Patra]

On 8/25/26 12:31 AM, Lorenzo Stoakes (ARM) wrote:
> On Tue, Aug 25, 2026 at 12:12:32AM -0700, Atish Patra wrote:
> > Reproduced and verified this series (patches 1-3) on 4vcpu guest running two different kernels
> > 1. mainline (commit: 77ae27fd98f3)
> > 2. Ubuntu Resolute 7.0.0-26 (production kernel hitting the issue in a VM)
> >
> > The Reproducer consisted of
> > 1. A debug patch a cmdline-gated stall between the two *pmd reads in vmalloc_to_page()
> > 2. One taskset-pinned insmod/rmmod worker per module over stock cfg80211/dummy/veth modules
> >
> > With the above reproducer, both BUG within seconds in unpatched kernel.
> > 1. Resolute in 0.71s at alternative.c:2564 (BUG_ON(!pages[0] ...), RAX=0)
> > 2. mainline at alternative.c:2473 (BUG_ON(memcmp(addr, src, len))).
> >
> > With patches 1-3: zero splats across 10 runs each (600s/11,378 module load/unload cycles on mainline and 1200s/55,980 module load/unload cycles on Resolute).
> Amazing, thanks!
>
> > Tested-by: Atish Patra<atishp@xxxxxxxx>
> I guess should be applied to patches 1-3 only strictly? Or perhaps 3/5?

Yes. 1-3 sounds good.


> > > --
> > > Sincerely yours,
> > > Mike.
> --
> Cheers, Lorenzo