Re: [PATCH] xen/arm: vtimer: Don't read/use the secure physical timer interrupt for ACPI

[Julien Grall <julien@xxxxxxx>]

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()".
Cheers,

--
Julien Grall