Re: [PATCH v3 15/16] iommu: introduce page response function

Jacob Pan
2017-12-08T20:39:07Z

On Fri, 8 Dec 2017 13:52:00 +0000
Jean-Philippe Brucker <jean-philippe.brucker@arm.com> wrote:

> On 07/12/17 21:51, Alex Williamson wrote:
> >> Agree, IOMMU driver cannot enforce it. I think VFIO layer can make
> >> sure page response come from the assigned device and its
> >> guest/container.
> >
> > Can we enforce it via the IOMMU/VFIO interface? If the response is
> > for a struct device, and not an rid/did embedded in a structure,
> > then vfio can pass it through w/o worrying about it, ie. response
> > comes in via ioctl with association to vfio device fd -> struct
> > vfio_device -> struct device, iommu driver fills in rid/did.
> > Thanks,
>
> Yes that's probably the best way, reporting faults and receiving
> responses on the device fd.
>
Just to put these ideas in to code. The IOMMU API used by VFIO has
struct device* (derived from fd), no did/rid (to be derived from
struct device by IOMMU driver.)

int intel_iommu_page_response(struct iommu_domain *domain, struct device *dev,
struct page_response_msg *msg)

IOMMU driver can further sanitize by checking whether this is a pending
page request for the device, and refcount outstanding PRQs.

Does it sound right?

/**
* Generic page response information based on PCI ATS and PASID spec.
* @addr: servicing page address
* @pasid: contains process address space ID, used in shared virtual
memory(SVM)
* @resp_code: response code
* @page_req_group_id: page request group index
* @type: group or stream/single page response
* @private_data: uniquely identify device-specific private data for an
* individual page response

*/
struct page_response_msg {
u64 addr;
u32 pasid;
u32 resp_code:4;
#define IOMMU_PAGE_RESP_SUCCESS 0
#define IOMMU_PAGE_RESP_INVALID 1
#define IOMMU_PAGE_RESP_FAILURE 0xF

u32 pasid_present:1;
u32 page_req_group_id : 9;
enum page_response_type type;
u32 private_data;
};