linux-kernel - RE: [PATCH 1/1] iommu/vt-d: Draining PRQ in sva unbind path when FPD bit set

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Message-ID: <BL1PR11MB52712961A13B55ED1DDCCFE28C042@BL1PR11MB5271.namprd11.prod.outlook.com>
Date: Tue, 17 Dec 2024 07:39:49 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Lu Baolu <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>, "Will
 Deacon" <will@...nel.org>, Robin Murphy <robin.murphy@....com>, "Liu, Yi L"
	<yi.l.liu@...el.com>
CC: "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/1] iommu/vt-d: Draining PRQ in sva unbind path when FPD
 bit set

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Tuesday, December 17, 2024 10:43 AM
> 
> When a device uses a PASID for SVA (Shared Virtual Address), it's possible
> that the PASID entry is marked as non-present and FPD bit set before the
> device flushes all ongoing DMA requests and removes the SVA domain. This
> can occur when an exception happens and the process terminates before the
> device driver stops DMA and calls the iommu driver to unbind the PASID.
> 
> There's no need to drain the PRQ in the mm release path. Instead, the PRQ
> will be drained in the SVA unbind path. But in such case,
> intel_pasid_tear_down_entry() only checks the presence of the pasid entry
> and returns directly.
> 
> Add the code to clear the FPD bit and drain the PRQ.
> 
> Suggested-by: Kevin Tian <kevin.tian@...el.com>
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>

Need a fix tag given the old code doesn't work correctly?

Reviewed-by: Kevin Tian <kevin.tian@...el.com>