Re: [Devel] [RFCv2 2/2] iommu/arm-smmu-v3:Enable ACPI based HiSilicon erratum 161010801

[Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>]

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On Tue, Jun 06, 2017 at 03:01:36PM +0000, Shameerali Kolothum Thodi wrote:

[...]

> > > +	irq_dom = pci_msi_get_device_domain(to_pci_dev(dev));
> > > +	if (irq_dom) {
> > > +		int	ret;
> > > +		u32	rid;
> > > +
> > > +		rid = pci_msi_domain_get_msi_rid(irq_dom,
> > to_pci_dev(dev));
> > > +		ret = iort_dev_find_its_base(dev, rid, 0, &base);
> > 
> > Well, here we use ITS id 0 which is fine as long as code in IORT uses the same
> > policy for getting the irq_domain (ie we want to reserve the ITS address
> > space that is actually used by the device to send IRQs not a a different one) it
> > is just a heads-up because I find this confusing.
> 
> Ok. Just to make it clear, 0 is the index into the ITS identifier
> list.  I noted that iort_get_device_domain() uses index 0 while
> retrieving the ITS identifier.  May be use the same approach here as
> well? ie, remove the index from function call?
> 
> I am not sure, how we can get the index info  though theoretically It
> is possible for the ITS group node having multiple ITSs.

Actually I think it would make sense to reserve ALL ITS regions a device
may be mapped to instead of just index 0 (ie in your case it is
equivalent); this leaves us some leeway as to choose which ITS the
device will be actually mapped to and this code does not have to care.

Lorenzo

>  
> > > +		if (!ret) {
> > > +			dev_info(dev, "SMMUv3:HW MSI resv addr
> > 0x%pa\n", &base);
> > > +			region = iommu_alloc_resv_region(base, SZ_128K,
> > > +							 prot,
> > IOMMU_RESV_MSI);
> > > +			return region;
> > > +		}
> > > +	}
> > > +
> > > +	return NULL;
> > > +}
> > > +#else
> > > +static struct iommu_resv_region *arm_smmu_acpi_alloc_hw_msi(struct
> > > +device *dev) {
> > > +	return NULL;
> > > +}
> > > +#endif
> > > +
> > >  static int arm_smmu_add_device(struct device *dev)  {
> > >  	int i, ret;
> > > @@ -1903,11 +1936,20 @@ static int arm_smmu_of_xlate(struct device
> > > *dev, struct of_phandle_args *args)  static void
> > arm_smmu_get_resv_regions(struct device *dev,
> > >  				      struct list_head *head)
> > >  {
> > > -	struct iommu_resv_region *region;
> > > +	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
> > > +	struct iommu_resv_region *region = NULL;
> > >  	int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
> > > +	struct arm_smmu_device *smmu;
> > > +
> > > +	smmu = arm_smmu_get_by_fwnode(fwspec->iommu_fwnode);
> > >
> > > -	region = iommu_alloc_resv_region(MSI_IOVA_BASE,
> > MSI_IOVA_LENGTH,
> > > -					 prot, IOMMU_RESV_SW_MSI);
> > > +	if (smmu && (smmu->options & ARM_SMMU_OPT_RESV_HW_MSI)
> > &&
> > > +		      dev_is_pci(dev))
> > > +		region = arm_smmu_acpi_alloc_hw_msi(dev);
> > 
> > Is it safe to carry on if arm_smmu_acpi_alloc_hw_msi() returns NULL here ?
> 
> It is just that PCIe devices won't be functional on this platforms as the endpoint will 
> be configured with ITS IOVA address. May be I should add some dev_warn() here.
> 
> Thanks,
> Shameer