Re: [PATCH v4 5/7] iommu/vt-d: Make device pasid attachment explicit

[Baolu Lu]

On 4/19/23 5:32 AM, Jacob Pan wrote:
> On Mon, 10 Apr 2023 10:46:02 +0800, Baolu Lu<baolu.lu@xxxxxxxxxxxxxxx>
> wrote:
>
> > On 4/8/23 2:05 AM, Jacob Pan wrote:
> > > @@ -2429,10 +2475,11 @@ static int __init si_domain_init(int hw)
> > >    	return 0;
> > >    }
> > >    
> > > -static int dmar_domain_attach_device(struct dmar_domain *domain,
> > > -				     struct device *dev)
> > > +static int dmar_domain_attach_device_pasid(struct dmar_domain *domain,
> > > +				     struct device *dev, ioasid_t
> > > pasid) {
> > >    	struct device_domain_info *info = dev_iommu_priv_get(dev);
> > > +	struct device_pasid_info *dev_pasid;
> > >    	struct intel_iommu *iommu;
> > >    	unsigned long flags;
> > >    	u8 bus, devfn;
> > > @@ -2442,43 +2489,57 @@ static int dmar_domain_attach_device(struct
> > > dmar_domain *domain, if (!iommu)
> > >    		return -ENODEV;
> > >    
> > > +	dev_pasid = kzalloc(sizeof(*dev_pasid), GFP_KERNEL);
> > > +	if (!dev_pasid)
> > > +		return -ENOMEM;
> > > +
> > >    	ret = domain_attach_iommu(domain, iommu);
> > >    	if (ret)
> > > -		return ret;
> > > +		goto exit_free;
> > > +
> > >    	info->domain = domain;
> > > +	dev_pasid->pasid = pasid;
> > > +	dev_pasid->dev = dev;
> > >    	spin_lock_irqsave(&domain->lock, flags);
> > > -	list_add(&info->link, &domain->devices);
> > > +	if (!info->dev_attached)
> > > +		list_add(&info->link, &domain->devices);
> > > +
> > > +	list_add(&dev_pasid->link_domain, &domain->dev_pasids);
> > >    	spin_unlock_irqrestore(&domain->lock, flags);
> > >    
> > >    	/* PASID table is mandatory for a PCI device in scalable
> > > mode. */ if (sm_supported(iommu) && !dev_is_real_dma_subdevice(dev)) {
> > >    		/* Setup the PASID entry for requests without PASID:
> > > */ if (hw_pass_through && domain_type_is_si(domain))
> > > -			ret = intel_pasid_setup_pass_through(iommu,
> > > domain,
> > > -					dev, PASID_RID2PASID);
> > > +			ret = intel_pasid_setup_pass_through(iommu,
> > > domain, dev, pasid); else if (domain->use_first_level)
> > > -			ret = domain_setup_first_level(iommu, domain,
> > > dev,
> > > -					PASID_RID2PASID);
> > > +			ret = domain_setup_first_level(iommu, domain,
> > > dev, pasid); else
> > > -			ret = intel_pasid_setup_second_level(iommu,
> > > domain,
> > > -					dev, PASID_RID2PASID);
> > > +			ret = intel_pasid_setup_second_level(iommu,
> > > domain, dev, pasid); if (ret) {
> > > -			dev_err(dev, "Setup RID2PASID failed\n");
> > > +			dev_err(dev, "Setup PASID %d failed\n", pasid);
> > >    			device_block_translation(dev);
> > > -			return ret;
> > > +			goto exit_free;
> > >    		}
> > >    	}
> > > +	/* device context already activated,  we are done */
> > > +	if (info->dev_attached)
> > > +		goto exit;
> > >    
> > >    	ret = domain_context_mapping(domain, dev);
> > >    	if (ret) {
> > >    		dev_err(dev, "Domain context map failed\n");
> > >    		device_block_translation(dev);
> > > -		return ret;
> > > +		goto exit_free;
> > >    	}
> > >    
> > >    	iommu_enable_pci_caps(info);
> > > -
> > > +	info->dev_attached = 1;
> > > +exit:
> > >    	return 0;
> > > +exit_free:
> > > +	kfree(dev_pasid);
> > > +	return ret;
> > >    }
> > >    
> > >    static bool device_has_rmrr(struct device *dev)
> > > @@ -4029,8 +4090,7 @@ static void device_block_translation(struct
> > > device *dev) iommu_disable_pci_caps(info);
> > >    	if (!dev_is_real_dma_subdevice(dev)) {
> > >    		if (sm_supported(iommu))
> > > -			intel_pasid_tear_down_entry(iommu, dev,
> > > -						    PASID_RID2PASID,
> > > false);
> > > +
> > > intel_iommu_detach_device_pasid(&info->domain->domain, dev,
> > > PASID_RID2PASID); else domain_context_clear(info);
> > >    	}
> > > @@ -4040,6 +4100,7 @@ static void device_block_translation(struct
> > > device *dev)
> > >    	spin_lock_irqsave(&info->domain->lock, flags);
> > >    	list_del(&info->link);
> > > +	info->dev_attached = 0;
> > >    	spin_unlock_irqrestore(&info->domain->lock, flags);
> > >    
> > >    	domain_detach_iommu(info->domain, iommu);
> > > @@ -4186,7 +4247,7 @@ static int intel_iommu_attach_device(struct
> > > iommu_domain *domain, if (ret)
> > >    		return ret;
> > >    
> > > -	return dmar_domain_attach_device(to_dmar_domain(domain), dev);
> > > +	return dmar_domain_attach_device_pasid(to_dmar_domain(domain),
> > > dev, PASID_RID2PASID); }
> > For VT-d driver, attach_dev and attach_dev_pasid have different
> > meanings. Merging them into one helper may lead to confusion. What do
> > you think of the following code? The dmar_domain_attach_device_pasid()
> > helper could be reused for attach_dev_pasid path.
> Per our previous discussion
> https://lore.kernel.org/lkml/ZAY4zd4OlgSz+puZ@xxxxxxxxxx/
> We wanted to remove the ordering dependency between attaching device and
> device_pasid. i.e. making the two equal at IOMMU API level.

Yes. That still holds.

> So from that perspective, attach_dev_pasid will include attach_dev if the
> device has not been attached. i.e.

I don't follow here. attach_dev and attach_dev_pasid are independent of
each other. So in any case, attach_dev_pasid shouldn't include
attach_dev.

> attach_dev includes set up device context and RID_PASID
> attach_dev_pasid also include set up device context and another PASID.

I guess that you are worrying about the case where the context entry and
pasid table are not setup yet in attach_dev_pasid path? In theory yes,
but not exist in reality. The best case is that we setup context entry
in probe_device path, but at present, perhaps we can simply check and
return failure in this case.

Any way, I'd suggest not mix two ops in a single function.

> No ordering requirement.

Best regards,
baolu