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

[Jason Gunthorpe]

> @@ -4821,21 +4821,36 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu)
>  	arm_smmu_cmdq_issue_cmd_with_sync(
>  		smmu, arm_smmu_make_cmd_op(CMDQ_OP_TLBI_NSNH_ALL));
>  
> -	/* Event queue */
> -	writeq_relaxed(smmu->evtq.q.q_base, smmu->base + ARM_SMMU_EVTQ_BASE);
> -	writel_relaxed(smmu->evtq.q.llq.prod, smmu->page1 + ARM_SMMU_EVTQ_PROD);
> -	writel_relaxed(smmu->evtq.q.llq.cons, smmu->page1 + ARM_SMMU_EVTQ_CONS);
> +	/*
> +	 * Event queue
> +	 *
> +	 * Do not enable in a kdump case, as the crashed kernel's CDs and page
> +	 * tables may be corrupted, triggering event spamming. A disabled queue
> +	 * simply discards new events, without raising any global error.
> +	 */
> +	if (!is_kdump_kernel()) {

same remark about a FEAT_EVTQ

> -	/* 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?

The logic still looks OK to me

-- 
Jason