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Subject: Re: [PATCH RFC 1/3] xen/privcmd: replace kcalloc() by kvcalloc() when
 allocating empty pages
To:     Jan Beulich <jbeulich@suse.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc:     Stefano Stabellini <sstabellini@kernel.org>,
        "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
        lkml <linux-kernel@vger.kernel.org>
References: <0f0db6fa-2604-9a0d-1138-0063b5a39a87@suse.com>
 <6d698901-98a4-05be-c421-bcd0713f5335@suse.com>
From:   Juergen Gross <jgross@suse.com>
Message-ID: <6e90efe0-4c0d-55d9-bff8-6da9b9614cd1@suse.com>
Date:   Thu, 23 Sep 2021 14:30:43 +0200
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From: Juergen Gross <jgross@suse.com>
To: Jan Beulich <jbeulich@suse.com>,
 Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
 "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
 lkml <linux-kernel@vger.kernel.org>
Message-ID: <6e90efe0-4c0d-55d9-bff8-6da9b9614cd1@suse.com>
Subject: Re: [PATCH RFC 1/3] xen/privcmd: replace kcalloc() by kvcalloc() when
 allocating empty pages
References: <0f0db6fa-2604-9a0d-1138-0063b5a39a87@suse.com>
 <6d698901-98a4-05be-c421-bcd0713f5335@suse.com>
In-Reply-To: <6d698901-98a4-05be-c421-bcd0713f5335@suse.com>

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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().
>=20
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

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

> ---
> RFC: I cannot really test this, as alloc_empty_pages() only gets used i=
n
>       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).
>=20
> 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 b=
e
> 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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