RE: [PATCH v3 08/10] iommu/arm-smmu-v3: Reserve any RMR regions associated with a dev

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>]

Hi Robin,

> -----Original Message-----
> From: Robin Murphy [mailto:robin.murphy@xxxxxxx]
> Sent: 07 May 2021 11:02
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx;
> iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
> Cc: Linuxarm <linuxarm@xxxxxxxxxx>; lorenzo.pieralisi@xxxxxxx;
> joro@xxxxxxxxxx; wanghuiqiang <wanghuiqiang@xxxxxxxxxx>; Guohanjun
> (Hanjun Guo) <guohanjun@xxxxxxxxxx>; steven.price@xxxxxxx;
> Sami.Mujawar@xxxxxxx; jon@xxxxxxxxxxxxx; eric.auger@xxxxxxxxxx
> Subject: Re: [PATCH v3 08/10] iommu/arm-smmu-v3: Reserve any RMR regions
> associated with a dev
> 
> On 2021-04-20 09:27, Shameer Kolothum wrote:
> > Get RMR regions associated with a dev reserved so that there is
> > a unity mapping for them in SMMU.
> >
> > Signed-off-by: Shameer Kolothum
> <shameerali.kolothum.thodi@xxxxxxxxxx>
> > ---
> >   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 29
> +++++++++++++++++++++
> >   1 file changed, 29 insertions(+)
> >
> > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > index 14e9c7034c04..8bacedf7bb34 100644
> > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > @@ -2531,6 +2531,34 @@ static int arm_smmu_of_xlate(struct device *dev,
> struct of_phandle_args *args)
> >   	return iommu_fwspec_add_ids(dev, args->args, 1);
> >   }
> >
> > +static bool arm_smmu_dev_has_rmr(struct arm_smmu_master *master,
> > +				 struct iommu_rmr *e)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < master->num_sids; i++) {
> > +		if (e->sid == master->sids[i])
> > +			return true;
> > +	}
> > +
> > +	return false;
> > +}
> > +
> > +static void arm_smmu_rmr_get_resv_regions(struct device *dev,
> > +					  struct list_head *head)
> > +{
> > +	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
> > +	struct arm_smmu_device *smmu = master->smmu;
> > +	struct iommu_rmr *rmr;
> > +
> > +	list_for_each_entry(rmr, &smmu->rmr_list, list) {
> > +		if (!arm_smmu_dev_has_rmr(master, rmr))
> > +			continue;
> > +
> > +		iommu_dma_get_rmr_resv_regions(dev, rmr, head);
> > +	}
> > +}
> > +
> 
> TBH I wouldn't have thought we need a driver-specific hook for this, or
> is it too painful to correlate fwspec->iommu_fwnode back to the relevant
> IORT node generically?

>From a quick look, I think I could get rid of the above with something like below,

------8<----
+static bool iommu_dma_dev_has_rmr(struct iommu_fwspec *fwspec,
+                                 struct iommu_rmr *e)
+{
+       int i;
+
+       for (i = 0; i < fwspec->num_ids; i++) {
+                if (e->sid == fwspec->ids[i])
+                        return true;
+        }
+
+        return false;
+}
+
+
+void iommu_dma_get_rmr_resv_regions(struct device *dev, struct list_head *list)
+{
+       struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
+       struct list_head rmr_list;
+       struct iommu_rmr *rmr;
+
+       INIT_LIST_HEAD(&rmr_list);
+       if (iommu_dma_get_rmrs(fwspec->iommu_fwnode, &rmr_list))
+               return;
        ...
+       list_for_each_entry(rmr, &rmr_list, list) {
+     
+       if (!iommu_dma_dev_has_rmr(fwspec, rmr)
+           continue;
+          ... 
+               region = iommu_alloc_resv_region(rmr->base_address,
+                                                rmr->length, prot,
+                                                type);
         ...
+       }
+}
 /**
  * iommu_dma_get_resv_regions - Reserved region driver helper
  * @dev: Device from iommu_get_resv_regions()
@@ -188,10 +242,11 @@ void iommu_dma_get_resv_regions(struct device *dev, struct list_head *list)
        if (!is_of_node(dev_iommu_fwspec_get(dev)->iommu_fwnode))
                iort_iommu_msi_get_resv_regions(dev, list);
 
+       iommu_dma_get_rmr_resv_regions(dev, list);
 }

----8<----

But looking at the SMMUv2 code, the fwspec->ids is MASK:SID, so I am not
sure the RMR sid can be compared directly to fwspec->ids above. Right? Or
is there a better way here?

Thanks,
Shameer


> 
> >   static void arm_smmu_get_resv_regions(struct device *dev,
> >   				      struct list_head *head)
> >   {
> > @@ -2545,6 +2573,7 @@ static void arm_smmu_get_resv_regions(struct
> device *dev,
> >   	list_add_tail(&region->list, head);
> >
> >   	iommu_dma_get_resv_regions(dev, head);
> > +	arm_smmu_rmr_get_resv_regions(dev, head);
> >   }
> >
> >   static bool arm_smmu_dev_has_feature(struct device *dev,
> >