linux-kernel - Re: [PATCH RFC 1/3] xen/privcmd: replace kcalloc() by kvcalloc() when allocating empty pages

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Date:   Thu, 23 Sep 2021 14:30:43 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Jan Beulich <jbeulich@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     Stefano Stabellini <sstabellini@...nel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC 1/3] xen/privcmd: replace kcalloc() by kvcalloc() when
 allocating empty pages

On 22.09.21 12:16, Jan Beulich wrote:
> Osstest has been suffering test failures for a little while from order-4
> allocation failures, resulting from alloc_empty_pages() calling
> kcalloc(). As there's no need for physically contiguous space here,
> switch to kvcalloc().
> 
> Signed-off-by: Jan Beulich <jbeulich@...e.com>

Reviewed-by: Juergen Gross <jgross@...e.com>

> ---
> RFC: I cannot really test this, as alloc_empty_pages() only gets used in
>       the auto-translated case (i.e. on Arm or PVH Dom0, the latter of
>       which I'm not trusting enough yet to actually start playing with
>       guests).
> 
> There are quite a few more kcalloc() where it's not immediately clear
> how large the element counts could possibly grow nor whether it would be
> fine to replace them (i.e. physically contiguous space not required).

I don't think those are an issue. Per default the sizes seem to be well
below a single page.

> I wasn't sure whether to Cc stable@ here; the issue certainly has been
> present for quite some time. But it didn't look to cause issues until
> recently.

I'd rather add it to stable. Its not as if the patch had a high
complexity.


Juergen

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