[PATCH v5 06/27] iommu/arm-smmu-v3: Consolidate clearing a CD table entry

[Mostafa Saleh]

On Mon, Mar 25, 2024 at 11:14:33AM -0300, Jason Gunthorpe wrote:
> On Fri, Mar 22, 2024 at 06:36:17PM +0000, Mostafa Saleh wrote:
> > > +void arm_smmu_clear_cd(struct arm_smmu_master *master, ioasid_t ssid)
> > > +{
> > > +	struct arm_smmu_cd target = {};
> > > +	struct arm_smmu_cd *cdptr;
> > > +
> > > +	if (!master->cd_table.cdtab)
> > > +		return;
> > > +	cdptr = arm_smmu_get_cd_ptr(master, ssid);
> > > +	if (WARN_ON(!cdptr))
> > > +		return;
> > 
> > I don’t understand the SVA code enough, but AFAICT, arm_smmu_sva_set_dev_pasid
> > can allocate the L2 CD table through arm_smmu_write_ctx_desc. 
> 
> Yes
> 
> > And if it failed
> > before allocating the CD table, then remove_dev_pasid would be
> > called, 
> 
> If it fails the core code should not call remove_dev_pasid() on a
> domain that was never attached. There is an obscure error unwinding
> issue in the core code Yi is looking to fix regarding multi-device
> PASID groups, but it is not a driver issue..
> 

I see, thanks for clarifying.

> > which warns here, the previous code would tolerate that, but that
> > might regress on systems with panic_on_warn, so I am not sure if
> > that is necessary.
> 
> Right, if it does hit it signals there is some error unwinding bug in
> the core code that should be resolved.
> 
> > Otherwise, Reviewed-by: Mostafa Saleh <smostafa at google.com>
> 
> Thanks,
> Jason

Thanks,
Mostafa