Re: [PATCH v7 4/5] xen/arm: add SGI handling for GICv3

[Julien Grall <julien.grall@linaro.org>]

On 07/11/2014 03:08 PM, Ian Campbell wrote:
> On Fri, 2014-07-11 at 14:43 +0100, Julien Grall wrote:
>>> diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
>>> index 3647497..e15d509 100644
>>> --- a/xen/arch/arm/vgic.c
>>> +++ b/xen/arch/arm/vgic.c
>>> @@ -343,6 +343,13 @@ out:
>>>          smp_send_event_check_mask(cpumask_of(v->processor));
>>>  }
>>>  
>>> +int vgic_emulate(struct cpu_user_regs *regs, union hsr hsr)
>>> +{
>>> +    struct vcpu *v = current;
>>> +
>>> +    return v->domain->arch.vgic.handler->emulate_sysreg(regs, hsr);
>>> +}
>>> +
>>
>> You didn't implement emulate_sysreg for vgic-v2. If the GICv3 is
>> misprogrammed, Xen will segfault...
> 
> Which isn't all that different to the BUG_ON(!->emulate_sysreg) which I
> would be in favour of, since misprogramming the GIC is a coding error...

I expect this function to be called often (everytime the guest is
sending an SGI), so adding BUG_ON(!->emulate_sysreg) will "slow down"
the emulation.

Implementing the callback emulate_sysreg for vgic-v2 and adding BUG
inside would be another solution.

Regards,

-- 
Julien Grall