Re: [PATCH v2 3/4] iommu/vt-d: Report page request faults for guest SVA

[Lu Baolu]

Hi Jean,

On 7/7/20 7:23 PM, Jean-Philippe Brucker wrote:
> On Mon, Jul 06, 2020 at 08:25:34AM +0800, Lu Baolu wrote:
> > A pasid might be bound to a page table from a VM guest via the iommu
> > ops.sva_bind_gpasid. In this case, when a DMA page fault is detected
> > on the physical IOMMU, we need to inject the page fault request into
> > the guest. After the guest completes handling the page fault, a page
> > response need to be sent back via the iommu ops.page_response().
> >
> > This adds support to report a page request fault. Any external module
> > which is interested in handling this fault should regiester a notifier
> > callback.
> >
> > Co-developed-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > Co-developed-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
> > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> [...]
> > +static int
> > +intel_svm_prq_report(struct device *dev, struct page_req_dsc *desc)
> > +{
> > +	struct iommu_fault_event event;
> > +	u8 bus, devfn;
> > +
> > +	memset(&event, 0, sizeof(struct iommu_fault_event));
> > +	bus = PCI_BUS_NUM(desc->rid);
> > +	devfn = desc->rid & 0xff;
> > +
> > +	/* Fill in event data for device specific processing */
> > +	event.fault.type = IOMMU_FAULT_PAGE_REQ;
> > +	event.fault.prm.addr = desc->addr;
> > +	event.fault.prm.pasid = desc->pasid;
> > +	event.fault.prm.grpid = desc->prg_index;
> > +	event.fault.prm.perm = prq_to_iommu_prot(desc);
> > +
> > +	/*
> > +	 * Set last page in group bit if private data is present,
> > +	 * page response is required as it does for LPIG.
> > +	 */
> > +	if (desc->lpig)
> > +		event.fault.prm.flags |= IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE;
> > +	if (desc->pasid_present)
> > +		event.fault.prm.flags |= IOMMU_FAULT_PAGE_REQUEST_PASID_VALID;
>
> Do you also need to set IOMMU_FAULT_PAGE_RESPONSE_NEEDS_PASID?  I added
> the flag to deal with devices that do not want a PASID value in their PRI
> response (bit 15 in the PCIe Page Request Status Register):
> https://lore.kernel.org/linux-iommu/20200616144712.748818-1-jean-philippe@xxxxxxxxxx/
> (applied by Joerg for v5.9)
>
> Grepping for pci_prg_resp_pasid_required() in intel/iommu.c it seems to
> currently reject devices that do not want a PASID in a PRI response, so I
> think you can set this flag unconditionally for now.

Yes. You are right. I will set this flag in the next version.

Best regards,
baolu

> Thanks,
> Jean
>
> > +	if (desc->priv_data_present) {
> > +		event.fault.prm.flags |= IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE;
> > +		event.fault.prm.flags |= IOMMU_FAULT_PAGE_REQUEST_PRIV_DATA;
> > +		memcpy(event.fault.prm.private_data, desc->priv_data,
> > +		       sizeof(desc->priv_data));
> > +	}
> > +
> > +	return iommu_report_device_fault(dev, &event);
> > +}