Re: [Qemu-devel] vfio for platform devices - 9/5/2012 - minutes

[Yoder Stuart-B08248]

Adding Will...

> -----Original Message-----
> From: Sethi Varun-B16395
> Sent: Friday, September 06, 2013 11:56 AM
> To: Yoder Stuart-B08248; Wood Scott-B07421; Bhushan Bharat-R65777; 'Peter
> Maydell'; 'Santosh Shukla'; 'Alex Williamson'; 'Alexander Graf';
> 'Antonios Motakis'; 'Christoffer Dall'; 'address@hidden'
> Cc: address@hidden; address@hidden; qemu-
> address@hidden
> Subject: RE: vfio for platform devices - 9/5/2012 - minutes
> 
> I have a query about the ARM SMMU driver. In the ARM smmu driver I see,
> that bus notifiers are registered for both amba and platform bus. Amba is
> the I/O interconnect, right? Why is bus notifier required for the amba
> bus?
> 
> -Varun
> 
> > -----Original Message-----
> > From: Yoder Stuart-B08248
> > Sent: Thursday, September 05, 2013 11:21 PM
> > To: Wood Scott-B07421; Sethi Varun-B16395; Bhushan Bharat-R65777;
> 'Peter
> > Maydell'; 'Santosh Shukla'; 'Alex Williamson'; 'Alexander Graf';
> > 'Antonios Motakis'; 'Christoffer Dall'; 'address@hidden'
> > Cc: address@hidden; address@hidden; qemu-
> > address@hidden
> > Subject: vfio for platform devices - 9/5/2012 - minutes
> >
> > We had a call with those interested and/or working on vfio for platform
> > devices.
> >
> > Participants: Scott Wood, Varun Sethi, Bharat Bhushan, Peter Maydell,
> >               Santosh Shukla, Alex Williamson, Alexander Graf,
> >               Antonios Motakis, Christoffer Dall, Kim Phillips,
> >               Stuart Yoder
> >
> > Several aspects to vfio for platform devices:
> >
> > 1. IOMMU groups
> >
> >  -iommu driver needs to register a bus notifier for the platform bus
> >   and create groups for relevant platform devices  -Antonios is looking
> > at this for several ARM IOMMUs  -PAMU (Freescale) driver already does
> > this
> >
> > 2. unbinding device from host
> >
> >  PCI:
> >    echo 0000:06:0d.0 > /sys/bus/pci/devices/0000:06:0d.0/driver/unbind
> >  Platform:
> >    echo ffe101300.dma >
> > /sys/bus/platform/devices/ffe101300.dma/driver/unbind
> >
> >  -don't believe there are issues or work to do here
> >
> > 3. binding device to vfio-platform driver
> >
> >  PCI:
> >    echo 1102 0002 > /sys/bus/pci/drivers/vfio-pci/new_id
> >
> >  -this is probably the least understood issue-- platform drivers
> >   register themselves with the bus for a specific "name"
> >   string.  That is matched with device tree "compatible" strings
> >   later to bind a device to a driver
> >  -we want is to have the vfio-platform driver to dynamically bind
> >   to a variety of platform devices previously unknown to
> >   vfio-platform
> >  -ideally unbinding and binding could be an atomic operation  -Alex W
> > pointed out that x86 could leverage this work so
> >   keep that in mind in what we design
> >  -Kim Phillips (Linaro) will start working on this
> >
> > 4. vfio kernel interface
> >
> >  -exposes regions and interrupts to user space via FDs  -there are
> 'info'
> > ioctls that allow getting info about
> >   regions/interrupts such as size and type of interrupt  -there is a
> > proposed extension to the 'info' ioctls that
> >   provides device tree paths, allowing user space to coorelate
> >   resources with the device tree
> >   (https://lists.cs.columbia.edu/pipermail/kvmarm/2013-
> July/006237.html)
> >
> > 5. QEMU
> >  -some key tasks
> >    -interacts with vfio kernel interface
> >    -registers memslots
> >    -needs to dynamically get device hooked up to VM's
> >     platform bus, including IRQs
> >    -needs to generate device tree node
> >  -a key point: we don't believe that platform device passthru
> >   in QEMU can be solved in a completely generic way.  There will
> >   need to be device specific code for each device type being passed
> >   through...to do things like generate device tree nodes  -in general
> we
> > expect a relatively small number of device types
> >   to be passed through to VMs
> >  -Alex Graf is working on dynamic creation of platform devices
> >   for the PPC e500 paravirt machine
> >  -see: http://lists.nongnu.org/archive/html/qemu-devel/2013-
> > 07/msg03614.html
> >  -first step is dynamically generating a virtual UART  -that sets the
> > stage to create and create vfio devices backed
> >   by real hardware
> >
> > There is a session at Linux Plumbers in a couple of weeks and further
> > discussions will happen there.
> >
> > Regards,
> > Stuart