linux-kernel - RE: [PATCH v2 2/2] iommu/vt-d: Fix NULL domain on device release

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Message-ID: <BN9PR11MB52764189F754ABF69D24E2AE8C232@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Mon, 4 Mar 2024 07:36:45 +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>, "Jason
 Gunthorpe" <jgg@...pe.ca>, "Badger, Eric" <ebadger@...estorage.com>
CC: "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 2/2] iommu/vt-d: Fix NULL domain on device release

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Thursday, February 29, 2024 5:46 PM
> 
> +
> +/*
> + * Cache invalidation for changes to a scalable-mode context table
> + * entry.
> + *
> + * Section 6.5.3.3 of the VT-d spec:
> + * - Device-selective context-cache invalidation;
> + * - Domain-selective PASID-cache invalidation to affected domains
> + *   (can be skipped if all PASID entries were not-present);
> + * - Domain-selective IOTLB invalidation to affected domains;

the spec talks about domain-selective but the code actually does
global invalidation.

> + * - Global Device-TLB invalidation to affected functions.
> + *
> + * Note that RWBF (Required Write-Buffer Flushing) capability has
> + * been deprecated for scable mode. Section 11.4.2 of the VT-d spec:
> + *
> + * HRWBF: Hardware implementations reporting Scalable Mode Translation
> + * Support (SMTS) as Set also report this field as Clear.

RWBF info is a bit weird given existing code doesn't touch it

> + */
> +static void sm_context_flush_caches(struct device *dev)
> +{
> +	struct device_domain_info *info = dev_iommu_priv_get(dev);
> +	struct intel_iommu *iommu = info->iommu;
> +
> +	iommu->flush.flush_context(iommu, 0, PCI_DEVID(info->bus, info-
> >devfn),
> +				   DMA_CCMD_MASK_NOBIT,
> DMA_CCMD_DEVICE_INVL);
> +	qi_flush_pasid_cache(iommu, 0, QI_PC_GLOBAL, 0);
> +	iommu->flush.flush_iotlb(iommu, 0, 0, 0, DMA_TLB_GLOBAL_FLUSH);
> +	devtlb_invalidation_with_pasid(iommu, dev, IOMMU_NO_PASID);
> +}
> +
> +static void context_entry_teardown_pasid_table(struct intel_iommu
> *iommu,
> +					       struct context_entry *context)
> +{
> +	context_clear_entry(context);
> +	if (!ecap_coherent(iommu->ecap))
> +		clflush_cache_range(context, sizeof(*context));

this is __iommu_flush_cache(). You can use it throughout this and
the 2nd series.

> +
> +void intel_pasid_teardown_sm_context(struct device *dev)
> +{

it's clearer to call it just intel_teardown_sm_context. pasid_table
is one field in the context entry. Having pasid leading is slightly
confusing.