linux-kernel - Re: [PATCH] regset: use vmalloc() for regset_get

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Date: Fri, 2 Feb 2024 12:38:38 -0800
From: Doug Anderson <dianders@...omium.org>
To: Mark Brown <broonie@...nel.org>
Cc: Dave Martin <Dave.Martin@....com>, Al Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Eric Biederman <ebiederm@...ssion.com>, Jan Kara <jack@...e.cz>, 
	Kees Cook <keescook@...omium.org>, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	Oleg Nesterov <oleg@...hat.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] regset: use vmalloc() for regset_get_alloc()

Hi,

On Fri, Feb 2, 2024 at 11:43 AM Mark Brown <broonie@...nel.org> wrote:
>
> On Fri, Feb 02, 2024 at 06:07:54PM +0000, Dave Martin wrote:
>
> > So, if the only reason for trying to migrate to vmalloc() is to cope
> > with an insanely sized regset on arm64, I think somehow or other we can
> > avoid that.
>
> With SME we do routinely see the full glory of the 64K regset for ZA in
> emulated systems so I think we have to treat it as an issue.

Ah, got it. 64K is much less likely to be as big of a problem (only an
order 4 allocation), but you're right that it's still a size where
kvmalloc() would be an improvement. With that in mind I'll plan to
send out a v2 of my patch where I use kvmalloc() instead of vmalloc()
and update the commit description a bit, including a link to this
thread. Then I will assume that others on this thread will move
forward with actually making the allocations smaller.

Please yell if the above sounds wrong. :-)

-Doug