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From: Doug Anderson <dianders@chromium.org>
Date: Thu, 15 Feb 2024 09:38:47 -0800
Message-ID: <CAD=FV=WSi=9V-Oe5eq0J-Uew45cX9JfgB8me-Nw-iFRfXm59Xg@mail.gmail.com>
Subject: Re: [PATCH v2] arm64/sve: Lower the maximum allocation for the SVE
 ptrace regset
To: Will Deacon <will@kernel.org>
Cc: Mark Brown <broonie@kernel.org>, Catalin Marinas <catalin.marinas@arm.com>, kernel-team@android.com, 
	Oleg Nesterov <oleg@redhat.com>, linux-kernel@vger.kernel.org, 
	Dave Martin <Dave.Martin@arm.com>, Al Viro <viro@zeniv.linux.org.uk>, 
	linux-arm-kernel@lists.infradead.org
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Hi,

On Thu, Feb 15, 2024 at 4:44=E2=80=AFAM Will Deacon <will@kernel.org> wrote=
:
>
> On Tue, 13 Feb 2024 18:24:38 +0000, Mark Brown wrote:
> > Doug Anderson observed that ChromeOS crashes are being reported which
> > include failing allocations of order 7 during core dumps due to ptrace
> > allocating storage for regsets:
> >
> >   chrome: page allocation failure: order:7,
> >           mode:0x40dc0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO),
> >           nodemask=3D(null),cpuset=3Durgent,mems_allowed=3D0
> >    ...
> >   regset_get_alloc+0x1c/0x28
> >   elf_core_dump+0x3d8/0xd8c
> >   do_coredump+0xeb8/0x1378
> >
> > [...]
>
> Applied to arm64 (for-next/fixes), thanks!
>
> [1/1] arm64/sve: Lower the maximum allocation for the SVE ptrace regset
>       https://git.kernel.org/arm64/c/2813926261e4

Thanks!

A side note to anyone trying to backport this is that there's a hidden
dependency of commit f171f9e4097d ("arm64/fp: Make SVE and SME length
register definition match architecture"). Without that dependency then
backporting ${SUBJECT} patch is just a no-op. ...backporting the
hidden dependency ends up giving merge conflicts, so for the purposes
of picking this to our 5.15 or earlier branches I went back to just
making the #define be 16 again like it was in v1.

-Doug