On 04/11/2022 12:30, Julien Grall wrote:
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> On Fri, 4 Nov 2022 at 12:09, Ayan Kumar Halder <ayank...@amd.com
> <mailto:ayank...@amd.com>> wrote:
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>
> On 04/11/2022 09:55, Michal Orzel wrote:
> > Hi Ayan,
> Hi Michal,
> >
> > On 31/10/2022 16:13, Ayan Kumar Halder wrote:
> >>
> >> Refer ARM DDI 0487G.b ID072021,
> >> D13.2.86 -
> >> ID_PFR1_EL1, AArch32 Processor Feature Register 1
> >>
> >> GIC, bits[31:28] == 0b0001 for GIC3.0 on Aarch32
> >>
> >> One can now enable GICv3 on AArch32 systems. However, ITS is not
> supported.
> >> The reason being currently we are trying to validate GICv3 on an
> AArch32_v8R
> >> system. Refer ARM DDI 0568A.c ID110520, B1.3.1,
> >> "A Generic Interrupt Controller (GIC) implemented with an Armv8-R PE
> must not
> >> implement LPI support."
> >>
> >> Updated SUPPORT.md.
> >>
> >> Signed-off-by: Ayan Kumar Halder <ayank...@amd.com
> <mailto:ayank...@amd.com>>
> >> ---
> >>
> >> Changed from :-
> >> v1 - 1. Remove "ARM_64 || ARM_32" as it is always true.
> >> 2. Updated SUPPORT.md.
> >>
> >> SUPPORT.md | 6 ++++++
> >> xen/arch/arm/Kconfig | 4 ++--
> >> xen/arch/arm/include/asm/cpufeature.h | 1 +
> >> 3 files changed, 9 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/SUPPORT.md b/SUPPORT.md
> >> index cf2ddfacaf..0137855c66 100644
> >> --- a/SUPPORT.md
> >> +++ b/SUPPORT.md
> >> @@ -82,6 +82,12 @@ Extension to the GICv3 interrupt controller to
> support MSI.
> >>
> >> Status: Experimental
> >>
> >> +### ARM/GICv3 + AArch32 ARM v8
> >> +
> >> +GICv3 is supported on AArch32 ARMv8 (besides AArch64)
> > Looking at the CONFIG_GICV3, it can be enabled on arm32, which at the
> moment
> > supports only ARMv7 (see __lookup_processor_type -> proc-v7.S).
> > What will prevent the user from enabling GICv3 for ARMv7 based CPU?
>
>
> Yes, this is my mistake.
>
> ARMv7 does not support GICv3.
>
>
> The same could be said for Xen on Aarch32 Armv8. This is not officially
> supported but works with some tweak in the lookup function.
>
>
>
> I should have introduced a new macro AArch32_v8R so that GICV3 is
> defined for it.
>
>
> I would rather not have such config. There are no issue to allow someone to
> build it for 32-bit because Xen is perfectly capable to detect which GIC
> version is in use.
>
> Instead we could simply disable GICv3 by default for arm32.
+1
~Michal
