Re: [PATCH v9 02/12] iommu/arm-smmu-v3: Skip EVTQ/PRIQ setup in kdump kernel

[Nicolin Chen <nicolinc@nvidia.com>]

On Fri, Aug 21, 2026 at 08:15:25PM -0300, Jason Gunthorpe wrote:
> > @@ -4821,21 +4821,36 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu)
> > -	/* PRI queue */
> > -	if (smmu->features & ARM_SMMU_FEAT_PRI) {
> > +	/*
> > +	 * PRI queue
> > +	 *
> > +	 * Do not enable in a kdump case, as we cannot serve page requests.
> > +	 */
> > +	if (!is_kdump_kernel() && (smmu->features & ARM_SMMU_FEAT_PRI)) {
> >  		writeq_relaxed(smmu->priq.q.q_base,
> 
> I'm reading this again and wondering why not drop FEAT_PRI much earlier so we
> don't need this is_kdump_kernel() here?

Yes. I added this:

@@ -5371,6 +5351,15 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
 	if (arm_smmu_sva_supported(smmu))
 		smmu->features |= ARM_SMMU_FEAT_SVA;
 
+       /*
+	* A kdump kernel wants neither queue: the crashed kernel's CDs and page
+	* tables might be corrupted, spamming events, and page requests cannot
+	* be served. A disabled queue discards new records without raising any
+	* global error.
+	*/
+       if (is_kdump_kernel())
+	       smmu->features &= ~(ARM_SMMU_FEAT_EVTQ | ARM_SMMU_FEAT_PRI);
+
 	dev_info(smmu->dev, "oas %lu-bit (features 0x%08x)\n",
 		 smmu->oas, smmu->features);

Thanks
Nicolin