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

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Date:   Mon, 25 Jul 2022 09:47:22 +0100
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     "Tian, Kevin" <kevin.tian@...el.com>
Cc:     Baolu Lu <baolu.lu@...ux.intel.com>,
        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()

On Mon, Jul 25, 2022 at 08:02:05AM +0000, Tian, Kevin wrote:
> > 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].

Ah yes, I can use that. Something explicit would help avoid breaking the
driver next time the core changes

> 
> > 
> > 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?

Today the SMMU driver keeps track of bonds, but the goal of this series is
to move that to the core.

Thanks,
Jean