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From: "Tian, Kevin" <kevin.tian@intel.com>
To: Ethan Zhao <haifeng.zhao@linux.intel.com>, "bhelgaas@google.com"
	<bhelgaas@google.com>, "baolu.lu@linux.intel.com" <baolu.lu@linux.intel.com>,
	"dwmw2@infradead.org" <dwmw2@infradead.org>, "will@kernel.org"
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	"lukas@wunner.de" <lukas@wunner.de>
CC: "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [RFC PATCH v9 1/5] iommu/vt-d: add flush_target_dev member to
 struct intel_iommu and pass device info to all ATS Invalidation functions
Thread-Topic: [RFC PATCH v9 1/5] iommu/vt-d: add flush_target_dev member to
 struct intel_iommu and pass device info to all ATS Invalidation functions
Thread-Index: AQHaOSM8aFc/Sn24n0WhEo68HXH5iLC+VZYA
Date: Thu, 28 Dec 2023 08:10:58 +0000
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References: <20231228001646.587653-1-haifeng.zhao@linux.intel.com>
 <20231228001646.587653-2-haifeng.zhao@linux.intel.com>
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> From: Ethan Zhao <haifeng.zhao@linux.intel.com>
> Sent: Thursday, December 28, 2023 8:17 AM
>
> @@ -181,6 +181,7 @@ static void __flush_svm_range_dev(struct intel_svm
> *svm,
>=20
>  	qi_flush_piotlb(sdev->iommu, sdev->did, svm->pasid, address, pages,
> ih);
>  	if (info->ats_enabled) {
> +		info->iommu->flush_target_dev =3D info->dev;
>  		qi_flush_dev_iotlb_pasid(sdev->iommu, sdev->sid, info-
> >pfsid,
>  					 svm->pasid, sdev->qdep, address,
>  					 order_base_2(pages));

this is wrong both in concept and function.

an iommu instance can be shared by many devices which may all have
ongoing ATS invalidation requests to handle. Using a per-iommu field
to store the flush target is limiting (and there is no lock protection at a=
ll).

if there is a real need of passing dev pointer to qi helpers, just change
the helper to accept an explicit parameter.