Re: [Xen-devel] [RFC PATCH 01/24] ARM: GICv3 ITS: parse and store ITS subnodes from hardware DT

[Andre Przywara <andre.przywara@xxxxxxx>]

Hi,

On 01/11/16 15:13, Julien Grall wrote:
> Hi Andre,
> 
> On 28/09/2016 19:24, Andre Przywara wrote:
>> Parse the DT GIC subnodes to find every ITS MSI controller the hardware
>> offers. Store that information in a list to both propagate all of them
>> later to Dom0, but also to be able to iterate over all ITSes.
>> This introduces an ITS Kconfig option.
>>
>> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
>> ---
>>  xen/arch/arm/Kconfig          |  5 ++++
>>  xen/arch/arm/Makefile         |  1 +
>>  xen/arch/arm/gic-its.c        | 67
>> +++++++++++++++++++++++++++++++++++++++++++
>>  xen/arch/arm/gic-v3.c         |  6 ++++
>>  xen/include/asm-arm/gic-its.h | 57 ++++++++++++++++++++++++++++++++++++
>>  5 files changed, 136 insertions(+)
>>  create mode 100644 xen/arch/arm/gic-its.c
>>  create mode 100644 xen/include/asm-arm/gic-its.h
>>
>> diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
>> index 797c91f..9fe3b8e 100644
>> --- a/xen/arch/arm/Kconfig
>> +++ b/xen/arch/arm/Kconfig
>> @@ -45,6 +45,11 @@ config ACPI
>>  config HAS_GICV3
>>      bool
>>
>> +config HAS_ITS
>> +        bool "GICv3 ITS MSI controller support"
>> +        depends on ARM_64
> 
> HAS_GICV3 will only be selected for 64-bit. It would need some rework to
> be supported on 32-bit. So I would drop this dependency.

OK, makes sense.

>> +        depends on HAS_GICV3
>> +
> 
> I am not convinced that we should (currently) let the user selecting the
> ITS support. It increases the test coverage (we have to test with and
> without). Do we expect people using GICv3 without ITS?

My concern was more that if it breaks something, people can just disable
it. But I have to go through the patches again to see if disabling it
really brings us something (because thinking about it I don't think so).

So given the test coverage argument I think we should at least enable it
by default for ARM64. Is there some "expert options" group somewhere
where we could insert the option to turn it off?


Cheers,
Andre.

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