linux-kernel - RE: [PATCH v10 08/12] iommu/sva: Refactoring iommu_sva_bind/unbind

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Date:   Mon, 25 Jul 2022 08:02:05 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Baolu Lu <baolu.lu@...ux.intel.com>
CC:     Jason Gunthorpe <jgg@...dia.com>, Joerg Roedel <joro@...tes.org>,
        Christoph Hellwig <hch@...radead.org>,
        "Raj, Ashok" <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        Zhangfei Gao <zhangfei.gao@...aro.org>,
        "Zhu, Tony" <tony.zhu@...el.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v10 08/12] iommu/sva: Refactoring
 iommu_sva_bind/unbind_device()

> From: Jean-Philippe Brucker <jean-philippe@...aro.org>
> Sent: Monday, July 25, 2022 3:39 PM
> 
> On Sun, Jul 24, 2022 at 09:48:15PM +0800, Baolu Lu wrote:
> > /*
> >  * iommu_detach_device_pasid() - Detach the domain from pasid of device
> >  * @domain: the iommu domain.
> >  * @dev: the attached device.
> >  * @pasid: the pasid of the device.
> >  *
> >  * The @domain must have been attached to @pasid of the @dev with
> >  * iommu_detach_device_pasid().
> >  */
> > void iommu_detach_device_pasid(struct iommu_domain *domain, struct
> device
> > *dev,
> > 			       ioasid_t pasid)
> > {
> > 	struct iommu_group *group = iommu_group_get(dev);
> > 	struct group_pasid *param;
> >
> > 	mutex_lock(&group->mutex);
> > 	domain->ops->set_dev_pasid(group->blocking_domain, dev, pasid);
> 
> Please also pass the old domain to this detach() function, so that the
> IOMMU driver doesn't have to keep track of them internally.

The old domain is already tracked in group->pasid_xarray and can
be retrieved using [dev, pasid].

> 
> In addition to clearing contexts, detach() also needs to invalidate TLBs,
> and for that the SMMU driver needs to know the old ASID (!= PASID) that
> was used by the context descriptor.
> 

Presumably both ASID and context descriptor are SMMU internal
knowledge. What exact information is required from the core API
and how is it done today?