linux-kernel - Re: [PATCH v1 14/14] iommu/arm-smmu-v3: Add arm_smmu_cache_invalidate

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Message-ID: <ZBxDavy99vg8OA9a@nvidia.com>
Date:   Thu, 23 Mar 2023 09:17:46 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Nicolin Chen <nicolinc@...dia.com>
Cc:     Robin Murphy <robin.murphy@....com>, will@...nel.org,
        eric.auger@...hat.com, kevin.tian@...el.com,
        baolu.lu@...ux.intel.com, joro@...tes.org,
        shameerali.kolothum.thodi@...wei.com, jean-philippe@...aro.org,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 14/14] iommu/arm-smmu-v3: Add
 arm_smmu_cache_invalidate_user

On Wed, Mar 22, 2023 at 01:57:23PM -0700, Nicolin Chen wrote:
> On Mon, Mar 20, 2023 at 07:19:34PM -0300, Jason Gunthorpe wrote:
> 
> > > IIUIC, the ioctl for the link of vSID/dev_id should happen at
> > > the stage when boot boots, while the HWPT alloc ioctl happens
> > > at CFGI_STE.
> > 
> > Yes
> >  
> > > > > What could be a good prototype of the ioctl? Would it be a VFIO
> > > > > device one or IOMMUFD one?
> > > > 
> > > > If we load the vSID table it should be a iommufd one, linked to the
> > > > ARM SMMUv3 driver and probably take in a pointer to an array of
> > > > vSID/dev_id pairs. Maybe an add/remove type of operation.
> > > 
> > > Will try some solution.
> > 
> > It is only necessary if you want to do batching
> > 
> > For non-batching the SID invalidation should be done differently with
> > a device_id input instead. That is a bit tricky to organize as you
> > want iommufd to get back a 'struct device *' from the ID.
> 
> I am wondering whether we need to have dev_id, i.e. IOMMUFD,
> in play with the link of pSID<->vSID, as I am thinking of a
> simplified approach by passing the vSID via the hwpt alloc
> structure when we allocate an S2 domain.

No, that doesn't make sense. the vSID is per-STE, the S2 domain is
fully shared. You can't put SID information in the iommu_domains.

JAson