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

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Message-ID: <3d0680fc-afba-e642-f88f-aac4e276c5a5@linux.intel.com>
Date:   Wed, 8 Jul 2020 10:13:02 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc:     baolu.lu@...ux.intel.com, iommu@...ts.linux-foundation.org,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] iommu/vt-d: Report page request faults for guest
 SVA

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@...ux.intel.com>
>> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
>> Co-developed-by: Liu Yi L <yi.l.liu@...el.com>
>> Signed-off-by: Liu Yi L <yi.l.liu@...el.com>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> ---
> [...]
>> +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@linaro.org/
> (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);
>> +}