Re: [PATCH v4 10/15] iommu/arm-smmu-v3: Support PRI Page Request in arm_smmu_handle_ppr()

On Fri, 11 Sep 2026 16:16:02 -0700
Nicolin Chen [off-list ref] wrote:

On Thu, Sep 10, 2026 at 05:14:05PM -0700, Jonathan Cameron wrote:

quoted

quoted

@@ -2380,9 +2381,47 @@ static void arm_smmu_handle_ppr(struct arm_smmu_device *smmu, u64 *evt)
 	last = FIELD_GET(PRIQ_0_PRG_LAST, evt[0]);
 	grpid = FIELD_GET(PRIQ_1_PRG_IDX, evt[1]);
 
-	dev_info(smmu->dev, "unexpected PRI request received:\n");
-	dev_info(smmu->dev,
-		 "\tsid 0x%08x.0x%05x: [%u%s] %sprivileged %s%s%s access at iova 0x%016llx\n",
+	/*
+	 * A PASID Stop Marker (LRW = 0b100) does not expect a response and
+	 * must be discarded before fault reporting: see the documentation
+	 * at iommu_report_device_fault().
+	 */
+	if (last && !(evt[0] & (PRIQ_0_PERM_READ | PRIQ_0_PERM_WRITE)))  

There is a bit of spec language about case where there is no PASID
LWR=0xb100 not being a stop marker, SSV == 0 and should be treated as
a PRI request. I'm not sure what that means in practice but maybe
a comment on why that case doesn't matter. Feels like breadcrumbs we
might need in future.  

That's a sharp one! I didn't find any the practical action was
suggested either.

I wonder if we should let it fall through instead of a return:

	/*
	 * A PASID Stop Marker (LRW = 0b100) does not expect a response and
	 * must be discarded before fault reporting: see the documentation
	 * at iommu_report_device_fault().
	 *
	 * Gate it on SSV, as without a PASID that same encoding is a PRI Page
	 * Request and it does expect a response. So let it fall through and be
	 * answered with a PRI_RESP_FAIL, since iommu_sva_handle_mm() rejects a
	 * PASID-less fault, or by the PRI_RESP_DENY issued below.
	 */
	if (last && ssv && !(evt[0] & (PRIQ_0_PERM_READ | PRIQ_0_PERM_WRITE)))
		return;

Thanks
Nicolin

Works for me.

J