Re: [RFC 2/9] iommu/vt-d: add bind_pasid_table function

[Jacob Pan]

On Thu, 22 Jun 2017 16:52:15 -0600
Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:

> On Wed, 14 Jun 2017 15:22:56 -0700
> Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx> wrote:
> 
> > Add Intel VT-d ops to the generic iommu_bind_pasid_table API
> > functions.
> > 
> > The primary use case is for direct assignment of SVM capable
> > device. Originated from emulated IOMMU in the guest, the request
> > goes through many layers (e.g. VFIO). Upon calling host IOMMU
> > driver, caller passes guest PASID table pointer (GPA) and size.
> > 
> > Device context table entry is modified by Intel IOMMU specific
> > bind_pasid_table function. This will turn on nesting mode and
> > matching translation type.
> > 
> > The unbind operation restores default context mapping.
> > 
> > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > Signed-off-by: Liu, Yi L <yi.l.liu@xxxxxxxxxxxxxxx>
> > Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
> > ---
> >  drivers/iommu/intel-iommu.c   | 109
> > ++++++++++++++++++++++++++++++++++++++++++
> > include/linux/dma_remapping.h |   1 + 2 files changed, 110
> > insertions(+)
> > 
> > diff --git a/drivers/iommu/intel-iommu.c
> > b/drivers/iommu/intel-iommu.c index fc2765c..1d5d9ab9 100644
> > --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -5430,6 +5430,111 @@ struct intel_iommu
> > *intel_svm_device_to_iommu(struct device *dev) 
> >  	return iommu;
> >  }
> > +
> > +static int intel_iommu_bind_pasid_table(struct iommu_domain
> > *domain,
> > +		struct device *dev, struct pasid_table_info
> > *pasidt_binfo) +{
> > +	struct intel_iommu *iommu;
> > +	struct context_entry *context;
> > +	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> > +	struct device_domain_info *info;
> > +	struct pci_dev *pdev;
> > +	u8 bus, devfn;
> > +	u16 did, *sid;
> > +	int ret = 0;
> > +	unsigned long flags;
> > +	u64 ctx_lo;
> > +
> > +	if (pasidt_binfo == NULL || pasidt_binfo->model !=
> > INTEL_IOMMU) {  
> 
> Clearly model cannot be used as a bit field so it would appear wrong
> to limit ourselves to 32 possible models by using it that way.
> 
agreed.
> > +		pr_warn("%s: Invalid bind request!\n", __func__);  
> 
> Let the callers deal with error reporting.
> 
ditto.
> > +		return -EINVAL;
> > +	}
> > +
> > +	iommu = device_to_iommu(dev, &bus, &devfn);
> > +	if (!iommu)
> > +		return -ENODEV;
> > +
> > +	sid = (u16 *)&pasidt_binfo->opaque;  
> 
> Failed to check length.
> 
ditto.
> 
> > +	/*
> > +	 * check SID, if it is not correct, return success to
> > allow looping
> > +	 * through all devices within a group
> > +	 */
> > +	if (PCI_DEVID(bus, devfn) != *sid)
> > +		return 0;
> > +
> > +	pdev = to_pci_dev(dev);  
> 
> Better test dev_is_pci() first!
> 
good point.
> > +	info = dev->archdata.iommu;
> > +	if (!info || !info->pasid_supported) {
> > +		pr_err("PCI %04x:%02x:%02x.%d: has no PASID
> > support\n",
> > +			       pci_domain_nr(pdev->bus), bus,
> > PCI_SLOT(devfn),
> > +			       PCI_FUNC(devfn));
> > +		ret = -EINVAL;
> > +		goto out;
> > +	}
> > +
> > +	if (pasidt_binfo->size > intel_iommu_get_pts(iommu)) {
> > +		pr_err("Invalid gPASID table size %llu, host size
> > %lu\n",
> > +			pasidt_binfo->size,
> > +			intel_iommu_get_pts(iommu));
> > +		ret = -EINVAL;
> > +		goto out;
> > +	}  
> 
> Different errnos here would be more useful to code that handles the
> return than these pr_err()s.
> 
OK.
> > +	spin_lock_irqsave(&iommu->lock, flags);
> > +	context = iommu_context_addr(iommu, bus, devfn, 0);
> > +	if (!context || !context_present(context)) {
> > +		pr_warn("%s: ctx not present for bus devfn
> > %x:%x\n",
> > +			__func__, bus, devfn);
> > +		spin_unlock_irqrestore(&iommu->lock, flags);
> > +		goto out;  
> 
> Return success?!
> 
good catch, should fail.
> > +	}
> > +	/* Anticipate guest to use SVM and owns the first level */
> > +	ctx_lo = context[0].lo;
> > +	ctx_lo |= CONTEXT_NESTE;
> > +	ctx_lo |= CONTEXT_PRS;
> > +	ctx_lo |= CONTEXT_PASIDE;
> > +	ctx_lo &= ~CONTEXT_TT_MASK;
> > +	ctx_lo |= CONTEXT_TT_DEV_IOTLB << 2;
> > +	context[0].lo = ctx_lo;
> > +
> > +	/* Assign guest PASID table pointer and size */
> > +	ctx_lo = (pasidt_binfo->ptr & VTD_PAGE_MASK) |
> > pasidt_binfo->size;
> > +	context[1].lo = ctx_lo;
> > +	/* make sure context entry is updated before flushing */
> > +	wmb();
> > +	did = dmar_domain->iommu_did[iommu->seq_id];
> > +	iommu->flush.flush_context(iommu, did,
> > +				(((u16)bus) << 8) | devfn,
> > +				DMA_CCMD_MASK_NOBIT,
> > +				DMA_CCMD_DEVICE_INVL);
> > +	iommu->flush.flush_iotlb(iommu, did, 0, 0,
> > DMA_TLB_DSI_FLUSH);
> > +	spin_unlock_irqrestore(&iommu->lock, flags);
> > +
> > +
> > +out:
> > +	return ret;
> > +}
> > +
> > +static int intel_iommu_unbind_pasid_table(struct iommu_domain
> > *domain,
> > +					struct device *dev)
> > +{
> > +	struct intel_iommu *iommu;
> > +	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> > +	u8 bus, devfn;
> > +
> > +	iommu = device_to_iommu(dev, &bus, &devfn);
> > +	if (!iommu)
> > +		return -ENODEV;
> > +	/*
> > +	 * REVISIT: we might want to clear the PASID table pointer
> > +	 * as part of context clear operation. Currently, it leaves
> > +	 * stale data but should be ignored by hardware since
> > PASIDE
> > +	 * is clear.
> > +	 */
> > +	/* ATS will be reenabled when remapping is restored */
> > +	pci_disable_ats(to_pci_dev(dev));  
> 
> dev_is_pci()?
> 
good to check, even thought intel iommu supports PCI only.
> > +	domain_context_clear(iommu, dev);
> > +	return domain_context_mapping_one(dmar_domain, iommu, bus,
> > devfn); +}
> >  #endif /* CONFIG_INTEL_IOMMU_SVM */
> >  
> >  const struct iommu_ops intel_iommu_ops = {
> > @@ -5438,6 +5543,10 @@ const struct iommu_ops intel_iommu_ops = {
> >  	.domain_free		= intel_iommu_domain_free,
> >  	.attach_dev		= intel_iommu_attach_device,
> >  	.detach_dev		= intel_iommu_detach_device,
> > +#ifdef CONFIG_INTEL_IOMMU_SVM
> > +	.bind_pasid_table	= intel_iommu_bind_pasid_table,
> > +	.unbind_pasid_table	=
> > intel_iommu_unbind_pasid_table, +#endif
> >  	.map			= intel_iommu_map,
> >  	.unmap			= intel_iommu_unmap,
> >  	.map_sg			= default_iommu_map_sg,
> > diff --git a/include/linux/dma_remapping.h
> > b/include/linux/dma_remapping.h index 9088407..85367b7 100644
> > --- a/include/linux/dma_remapping.h
> > +++ b/include/linux/dma_remapping.h
> > @@ -27,6 +27,7 @@
> >  
> >  #define CONTEXT_DINVE		(1ULL << 8)
> >  #define CONTEXT_PRS		(1ULL << 9)
> > +#define CONTEXT_NESTE		(1ULL << 10)
> >  #define CONTEXT_PASIDE		(1ULL << 11)
> >  
> >  struct intel_iommu;