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

[Lorenzo Stoakes (ARM)]

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?

>
> > --
> > Sincerely yours,
> > Mike.
> >

--
Cheers, Lorenzo