linux-kernel - Re: [PATCH v6 13/14] iommu/arm-smmu-v3: Report events that belong to devices attached to vIOMMU

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Message-ID: <20250218171821.GG4099685@nvidia.com>
Date: Tue, 18 Feb 2025 13:18:21 -0400
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: kevin.tian@...el.com, corbet@....net, will@...nel.org, joro@...tes.org,
	suravee.suthikulpanit@....com, robin.murphy@....com,
	dwmw2@...radead.org, baolu.lu@...ux.intel.com, shuah@...nel.org,
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org,
	eric.auger@...hat.com, jean-philippe@...aro.org, mdf@...nel.org,
	mshavit@...gle.com, shameerali.kolothum.thodi@...wei.com,
	smostafa@...gle.com, ddutile@...hat.com, yi.l.liu@...el.com,
	patches@...ts.linux.dev
Subject: Re: [PATCH v6 13/14] iommu/arm-smmu-v3: Report events that belong to
 devices attached to vIOMMU

On Fri, Jan 24, 2025 at 04:30:42PM -0800, Nicolin Chen wrote:

> @@ -1831,31 +1831,30 @@ static int arm_smmu_handle_event(struct arm_smmu_device *smmu,
>  		return -EOPNOTSUPP;
>  	}

There is still the filter at the top:

	switch (event->id) {
	case EVT_ID_TRANSLATION_FAULT:
	case EVT_ID_ADDR_SIZE_FAULT:
	case EVT_ID_ACCESS_FAULT:
	case EVT_ID_PERMISSION_FAULT:
		break;
	default:
		return -EOPNOTSUPP;
	}

Is that right here or should more event types be forwarded to the
guest?
  
>  	mutex_lock(&smmu->streams_mutex);
[..]
  
> -	ret = iommu_report_device_fault(master->dev, &fault_evt);
> +	if (event->stall) {
> +		ret = iommu_report_device_fault(master->dev, &fault_evt);
> +	} else {
> +		down_read(&master->vmaster_rwsem);

This already holds the streams_mutex across all of this, do you think
we should get rid of the vmaster_rwsem and hold the streams_mutex on
write instead?

Jason