Re: [PATCH] arm/gic-v3: Fix driver probe fail on GICv4 hardware

[Julien Grall <julien.grall@arm.com>]

On 27/05/16 14:48, Shanker Donthineni wrote:
> Hi Julien,

Hello Shanker,

> On 05/27/2016 07:35 AM, Julien Grall wrote:
>> On 27/05/16 00:59, Shanker Donthineni wrote:
>>> The current driver probe fails on hardware which has GICv4 version,
>>> even though it is fully compatible to GICv3. This patch fixes the
>>> issue by registering the same probe function for GICv4 hardware.
>>>
>>> Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
>>> ---
>>>    xen/arch/arm/gic-v3.c     | 13 +++++++++++++
>>>    xen/include/asm-arm/gic.h |  1 +
>>>    2 files changed, 14 insertions(+)
>>>
>>> diff --git a/xen/arch/arm/gic-v3.c b/xen/arch/arm/gic-v3.c
>>> index a095064..594cf6e 100644
>>> --- a/xen/arch/arm/gic-v3.c
>>> +++ b/xen/arch/arm/gic-v3.c
>>> @@ -1604,10 +1604,23 @@ static int __init gicv3_acpi_preinit(const void *data)
>>>        return 0;
>>>    }
>>>
>>> +static int __init gicv4_acpi_preinit(const void *data)
>>> +{
>>> +    gicv3_info.hw_version = GIC_V4;
>>
>> It will crash Xen as soon as DOM0 is created (see the BUG() in arch_domain_create). Please test any patch before sending on the ML.
>>
>> Anyway, there is no support of GICv4 in Xen. Instead Xen will drive it using the GICv3 driver. So the hardware version should be GIC_V3 here.
>>
> Yes, I know I am going to fix in a separate to fix dom0 boot issue some thing like below.

This should have been in the same patch or before. There is no point to 
have a patch adding support for GICv4 with ACPI which will lead to an 
obscure crash (a BUG() rather than a panic with a nice message).

>   diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> index 1365b4a..56a47f5 100644
> --- a/xen/arch/arm/domain.c
> +++ b/xen/arch/arm/domain.c
> @@ -571,6 +571,11 @@ int arch_domain_create(struct domain *d, unsigned int domcr_flags,
>               d->arch.vgic.version = GIC_V3;
>               break;
>
> +        case GIC_V4:
> +            config->gic_version = XEN_DOMCTL_CONFIG_GIC_V3;
> +            d->arch.vgic.version = GIC_V3;
> +            break;

As mentioned in my previous mail, there is no support of GICv4 in Xen. 
Although the GICv3 driver is supporting this hardware.So we should not 
advertise GIC_V4 outside of the driver until Xen will get enough 
knowledge of GICv4 which will require sensible change in the generic code.

Regards,

-- 
Julien Grall

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