linux-kernel - Re: [PATCH v3 6/7] iommu/vt-d: Implement set_dev

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Date:   Mon, 3 Apr 2023 14:48:27 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Joerg Roedel <joro@...tes.org>, dmaengine@...r.kernel.org,
        vkoul@...nel.org, Will Deacon <will@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        "Zanussi, Tom" <tom.zanussi@...el.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v3 6/7] iommu/vt-d: Implement set_dev_pasid domain op

Hi Baolu,

On Sat, 1 Apr 2023 21:48:36 +0800, Baolu Lu <baolu.lu@...ux.intel.com>
wrote:

> On 2023/4/1 7:11, Jacob Pan wrote:
> > Devices that use ENQCMDS to submit work on buffers mapped by DMA API
> > must attach a PASID to the default domain of the device. In preparation
> > for this use case, this patch implements set_dev_pasid() for the
> > default_domain_ops.
> > 
> > If the device context has not been set up prior to this call, this will
> > set up the device context in addition to PASID attachment.
> > 
> > Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > ---
> >   drivers/iommu/intel/iommu.c | 21 +++++++++++++++++++++
> >   1 file changed, 21 insertions(+)
> > 
> > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > index 52b9d0d3a02c..1ad9c5a4bd8f 100644
> > --- a/drivers/iommu/intel/iommu.c
> > +++ b/drivers/iommu/intel/iommu.c
> > @@ -4784,6 +4784,26 @@ static void intel_iommu_remove_dev_pasid(struct
> > device *dev, ioasid_t pasid) domain_detach_iommu(dmar_domain,
> > info->iommu); }
> >   
> > +static int intel_iommu_attach_device_pasid(struct iommu_domain *domain,
> > +					   struct device *dev,
> > ioasid_t pasid) +{
> > +	struct device_domain_info *info = dev_iommu_priv_get(dev);
> > +	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> > +	struct intel_iommu *iommu = info->iommu;
> > +	int ret;
> > +
> > +	if (!pasid_supported(iommu))
> > +		return -ENODEV;  
> 
> As the domain ID will be set to the pasid entry, need to get a refcount
> of the domain ID. Call domain_attach_iommu() here, and release it after
> the pasid entry is torn down.
dmar_domain_attach_device_pasid() below will call domain_attach_iommu() and
release in intel_iommu_remove_dev_pasid(). The previous patch has
consolidated the code path with device attachment.
would it be sufficient?

> > +	ret = prepare_domain_attach_device(domain, dev);
> > +	if (ret)
> > +		return ret;
> > +
> > +	return dmar_domain_attach_device_pasid(dmar_domain, dev,
> > pasid); +}
> > +
> > +
> > +
> >   const struct iommu_ops intel_iommu_ops = {
> >   	.capable		= intel_iommu_capable,
> >   	.domain_alloc		= intel_iommu_domain_alloc,
> > @@ -4803,6 +4823,7 @@ const struct iommu_ops intel_iommu_ops = {
> >   #endif
> >   	.default_domain_ops = &(const struct iommu_domain_ops) {
> >   		.attach_dev		=
> > intel_iommu_attach_device,
> > +		.set_dev_pasid          =
> > intel_iommu_attach_device_pasid, .map_pages		=
> > intel_iommu_map_pages, .unmap_pages		=
> > intel_iommu_unmap_pages, .iotlb_sync_map		=
> > intel_iommu_iotlb_sync_map,  
> 
> Best regards,
> baolu


Thanks,

Jacob