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

[Jean-Philippe Brucker]

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

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

Thanks,
Jean