Hi Jean,
On 2018/8/31 21:34, Jean-Philippe Brucker wrote:
On 27/08/18 09:06, Xu Zaibo wrote:
+struct vfio_iommu_type1_bind_process {
+ __u32 flags;
+#define VFIO_IOMMU_BIND_PID (1 << 0)
+ __u32 pasid;
As I am doing some works on the SVA patch set. I just consider why the
user space need this pasid.
Maybe, is it much more reasonable to set the pasid into all devices
under the vfio container by
a call back function from 'vfio_devices' while
'VFIO_IOMMU_BIND_PROCESS' CMD is executed
in kernel land? I am not sure because there exists no suitable call back
in 'vfio_device' at present.
When using vfio-pci, the kernel doesn't know how to program the PASID
into the device because the only kernel driver for the device is the
generic vfio-pci module. The PCI specification doesn't describe a way of
setting up the PASID, it's vendor-specific. Only the userspace
application owning the device (and calling VFIO_IOMMU_BIND) knows how to
do it, so we return the allocated PASID.
Note that unlike vfio-mdev where applications share slices of a
function, with vfio-pci one application owns the whole function so it's
safe to let userspace set the PASID in hardware. With vfio-mdev it's the
kernel driver that should be in charge of setting the PASID as you
described, and we wouldn't have a reason to return the PASID in the
vfio_iommu_type1_bind_process structure.
Understood. But I still get the following confusion:
As one application takes a whole function while using VFIO-PCI, why do
the application and the
function need to enable PASID capability? (Since just one I/O page table
is enough for them.)
Maybe I misunderstood, hope you can help me clear it. Thank you very much.
Thanks,
Zaibo
.
