[PATCH v12 10/10] iommu/arm-smmu-v3: Add stall support for platform devices

[Zhou Wang]

On 2021/2/1 19:14, Jean-Philippe Brucker wrote:
> Hi Zhou,
> 
> On Mon, Feb 01, 2021 at 09:18:42AM +0800, Zhou Wang wrote:
>>> @@ -1033,8 +1076,7 @@ int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain, int ssid,
>>>  			FIELD_PREP(CTXDESC_CD_0_ASID, cd->asid) |
>>>  			CTXDESC_CD_0_V;
>>>  
>>> -		/* STALL_MODEL==0b10 && CD.S==0 is ILLEGAL */
>>> -		if (smmu->features & ARM_SMMU_FEAT_STALL_FORCE)
>>> +		if (smmu_domain->stall_enabled)
>>
>> Could we add ssid checking here? like: if (smmu_domain->stall_enabled && ssid).
>> The reason is if not CD.S will also be set when ssid is 0, which is not needed.
> 
> Some drivers may want to get stall events on SSID 0:
> https://lore.kernel.org/kvm/20210125090402.1429-1-lushenming@huawei.com/#t

Hi Jean,

I did not notice this before. Yes, if we need to support IOPF in vfio, we
need enable stall events on SSID 0.

> 
> Are you seeing an issue with stall events on ssid 0?  Normally there
> shouldn't be any fault on this context, but if they happen and no handler

It happened that there is bug in the test code of HiSilicon HPRE crypto driver.
We used a wrong iova which triggered a SMMU event with stall bit :)

> is registered, the SMMU driver will just abort them and report them like a
> non-stall event.

It will report event 0x10 with stall bit.

Best,
Zhou

> 
> Thanks,
> Jean
> 
> .
>