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Re: [PATCH 2/3] xen/common: llc-coloring: Fix off-by-one in parse_color_config()


  • To: Luca Fancellu <Luca.Fancellu@xxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Thu, 9 Apr 2026 14:48:59 +0200
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  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>
  • Delivery-date: Thu, 09 Apr 2026 12:49:05 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 09.04.2026 14:22, Luca Fancellu wrote:
>> On 9 Apr 2026, at 12:39, Michal Orzel <michal.orzel@xxxxxxx> wrote:
>>
>> The check uses >= to compare the total number of colors against
>> max_num_colors (which is ARRAY_SIZE of the colors array).  This
>> incorrectly rejects input that would exactly fill the array.
>>
>> For example, with NR_LLC_COLORS=16, specifying 1 color for Xen and 15
>> for dom0 would fail.
>>
>> Change >= to > so that exactly filling the array is permitted.
>>
>> Fixes: 95ef5ddf8a ("xen/arm: add Dom0 cache coloring support")
>> Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
>> ---
> 
> Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>

Did you see Andrew's reply? If that earlier (recent) commit was wrong, I
think a 2nd Fixes: tag may be needed here. For now I can't help the
impression though that there might have been a re-basing mistake, where
that re-base may have wanted to result in this patch dissolving into
nothing. Yet of course I'm all ears to learn otherwise.

Jan



 


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