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Re: [for-4.18] [PATCH v2] ARM: GICv3 ITS: flush caches for newly allocated ITT
- To: Julien Grall <julien@xxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Mon, 25 Sep 2023 22:19:47 +0000
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- Cc: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stewart Hildebrand <stewart.hildebrand@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
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- Thread-topic: [for-4.18] [PATCH v2] ARM: GICv3 ITS: flush caches for newly allocated ITT
Hi Julien,
> On Sep 26, 2023, at 02:33, Julien Grall <julien@xxxxxxx> wrote:
>
> Hi,
>
> (Adding [for-4.18] in the title for Henry to spot the request)
Thanks!
>
> On 22/09/2023 23:27, Volodymyr Babchuk wrote:
>> ITS manages Device Tables and Interrupt Translation Tables on its own,
>> so generally we are not interested in maintaining any coherence with
>> CPU's view of those memory regions, except one case: ITS requires that
>> Interrupt Translation Tables should be initialized with
>> zeroes. Existing code already does this, but it does not cleans
>> caches afterwards. This means that ITS may see un-initialized ITT and
>> CPU can overwrite portions of ITT later, when it finally decides to
>> flush caches. Visible effect of this issue that there are not
>> interrupts delivered from a device.
>> Fix this by calling clean_and_invalidate_dcache_va_range() for newly
>> allocated ITT.
>
> I would consider to add:
>
> Fixes: 69082e1c210d ("ARM: GICv3 ITS: introduce device mapping")
>
>> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
>
> Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
>
> @Henry, this patch should be low-risk. We are cleaning & invalidating the
> cache, so there should be no change for platform not requiring cache
> maintenance. This should hopefully had support for more platform. Note that
> the GICv3 ITS feature is still experimental.
>
> Based on what I wrote above, would you be OK to have this patch in 4.18?
Yes, I was about to ask the same question but somehow forgot it. This is a quite
low risk patch and I think it is fine to have this in 4.18, so if the "Fixes”
tag
can be added on commit, please also add:
Release-acked-by: Henry Wang <Henry.Wang@xxxxxxx>
Kind regards,
Henry
>
> Cheers,
>
> --
> Julien Grall
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