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Re: [PATCH] xen/arm: vtimer: Don't read/use the secure physical timer interrupt for ACPI
- To: Julien Grall <julien@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Michal Orzel <michal.orzel@xxxxxxx>
- Date: Fri, 6 Oct 2023 11:59:37 +0200
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- Cc: <Henry.Wang@xxxxxxx>, <dan.driscoll@xxxxxxxxxxx>, <arvind.raghuraman@xxxxxxxxxxx>, Julien Grall <jgrall@xxxxxxxxxx>, "Stefano Stabellini" <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Fri, 06 Oct 2023 09:59:57 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hi Julien,
On 06/10/2023 11:43, Julien Grall wrote:
>
>
> On 05/10/2023 21:15, Michal Orzel wrote:
>> Hi Julien,
>
> Hi Michal,
>
>> On 05/10/2023 18:54, Julien Grall wrote:
>>>
>>>
>>> From: Julien Grall <jgrall@xxxxxxxxxx>
>>>
>>> Per ACPI 6.5 section 5.2.25 ("Generic Timer Description Table (GTDT)"),
>>> the fields "Secure EL1 Timer GSIV/Flags" are optional and an OS running
>>> in non-secure world is meant to ignore the values.
>>>
>>> However, Xen is trying to reserve the value. When booting on Graviton
>>> 2 metal instances, this would result to crash a boot because the
>>> value is 0 which is already reserved (I haven't checked for which device).
>> Per my understanding it is not reserved by any device.
>> 0 means SGI and for SGIs we pre-reserve the bits in allocated_irqs at the
>> very start.
>
> Ah yes good point. Somehow, I had in mind that PPI was starting at 0
> '^^. How about replacing the paragraph with:
>
> "However, Xen is trying to reserve the value. The ACPI tables for
> Graviton 2 metal instances will provide the value 0 which is not a
> correct PPI (PPIs start at 16) and would have in fact been already
> reserved by Xen as this is an SGI. Xen will hit the BUG() and panic()".
Yes, this sounds better. With that:
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
~Michal
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