linux-kernel - RE: [PATCH 1/1] iommu/vt-d: Make intel_iommu_drain_pasid

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Message-ID: <BN9PR11MB5276B3F78599A00476AA2CDC8CE72@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Mon, 20 Jan 2025 09:26:30 +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>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH 1/1] iommu/vt-d: Make intel_iommu_drain_pasid_prq() cover
 faults for RID

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Monday, January 20, 2025 4:02 PM
> 
> This driver supports page faults on PCI RID since commit <9f831c16c69e>
> ("iommu/vt-d: Remove the pasid present check in prq_event_thread") by
> allowing the reporting of page faults with the pasid_present field cleared
> to the upper layer for further handling. The fundamental assumption here
> is that the detach or replace operations act as a fence for page faults.
> This implies that all pending page faults associated with a specific RID
> or PASID are flushed when a domain is detached or replaced from a device
> RID or PASID.
> 
> However, the intel_iommu_drain_pasid_prq() helper does not correctly
> handle faults for RID. This leads to faults potentially remaining pending
> in the iommu hardware queue even after the domain is detached, thereby
> violating the aforementioned assumption.
> 
> Fix this issue by extending intel_iommu_drain_pasid_prq() to cover faults
> for RID.
> 
> Fixes: 9f831c16c69e ("iommu/vt-d: Remove the pasid present check in
> prq_event_thread")
> Cc: stable@...r.kernel.org
> Suggested-by: Kevin Tian <kevin.tian@...el.com>
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  drivers/iommu/intel/prq.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/intel/prq.c b/drivers/iommu/intel/prq.c
> index c2d792db52c3..043f02d7b460 100644
> --- a/drivers/iommu/intel/prq.c
> +++ b/drivers/iommu/intel/prq.c
> @@ -87,7 +87,8 @@ void intel_iommu_drain_pasid_prq(struct device *dev,
> u32 pasid)
>  		struct page_req_dsc *req;
> 
>  		req = &iommu->prq[head / sizeof(*req)];
> -		if (!req->pasid_present || req->pasid != pasid) {
> +		if (req->rid != sid ||
> +		    (req->pasid_present && req->pasid != pasid)) {
>  			head = (head + sizeof(*req)) & PRQ_RING_MASK;
>  			continue;
>  		}

Ah you'd also want to skip (!req->pasid_present &&
pasid != IOMMU_NO_PASID)