On Tue, 2016-01-26 at 15:41 +0800, Jike Song wrote:
> On 01/26/2016 05:30 AM, Alex Williamson wrote:
> > [cc +Neo @Nvidia]
> >
> > Hi Jike,
> >
> > On Mon, 2016-01-25 at 19:34 +0800, Jike Song wrote:
> > > On 01/20/2016 05:05 PM, Tian, Kevin wrote:
> > > > I would expect we can spell out next level tasks toward above
> > > > direction, upon which Alex can easily judge whether there are
> > > > some common VFIO framework changes that he can help :-)
> > >
> > > Hi Alex,
> > >
> > > Here is a draft task list after a short discussion w/ Kevin,
> > > would you please have a look?
> > >
> > > Bus Driver
> > >
> > > { in i915/vgt/xxx.c }
> > >
> > > - define a subset of vfio_pci interfaces
> > > - selective pass-through (say aperture)
> > > - trap MMIO: interface w/ QEMU
> >
> > What's included in the subset? Certainly the bus reset ioctls really
> > don't apply, but you'll need to support the full device interface,
> > right? That includes the region info ioctl and access through the vfio
> > device file descriptor as well as the interrupt info and setup ioctls.
> >
>
> [All interfaces I thought are via ioctl:) For other stuff like file
> descriptor we'll definitely keep it.]
>
> The list of ioctl commands provided by vfio_pci:
>
> - VFIO_DEVICE_GET_PCI_HOT_RESET_INFO
> - VFIO_DEVICE_PCI_HOT_RESET
>
> As you said, above 2 don't apply. But for this:
>
> - VFIO_DEVICE_RESET
>
> In my opinion it should be kept, no matter what will be provided in
> the bus driver.
Yes, the DEVICE_INFO ioctl describes whether it's present, I would
encourage implementing it.
> - VFIO_PCI_ROM_REGION_INDEX
> - VFIO_PCI_VGA_REGION_INDEX
>
> I suppose above 2 don't apply neither? For a vgpu we don't provide a
> ROM BAR or VGA region.
Right, these aren't ioctls, just indexes into the REGION_INFO ioctl,
they're optional.
> - VFIO_DEVICE_GET_INFO
> - VFIO_DEVICE_GET_REGION_INFO
> - VFIO_DEVICE_GET_IRQ_INFO
> - VFIO_DEVICE_SET_IRQS
>
> Above 4 are needed of course.
>
> We will need to extend:
>
> - VFIO_DEVICE_GET_REGION_INFO
>
>
> a) adding a flag: DONT_MAP. For example, the MMIO of vgpu
> should be trapped instead of being mmap-ed.
There's already an MMAP flag, mmap is only allowed when this is set, so
there's no need for the anti-flag. I'm also working on support for
sparse mmap capabilities so that within a region some portions can
support mmap.
> b) adding other information. For example, for the OpRegion, QEMU need
> to do more than mmap a region, it has to:
>
> - allocate a region
> - copy contents from somewhere in host to that region
> - mmap it to guest
>
>
> I remember you already have a prototype for this?
Yes, I'm working on this currently, it will by a device specific region
and QEMU can either copy the contents to a new buffer in guest memory
or provided trapped access to the host opregion. I thought vgpus
weren't going to need opregions though, I figured it was more for GVT-d
support. Thanks,
Alex
