> From: Cornelia Huck [mailto:cohuck@xxxxxxxxxx] > Sent: Wednesday, January 15, 2020 8:30 PM > To: Liu, Yi L <yi.l.liu@xxxxxxxxx> > Subject: Re: [PATCH v4 11/12] samples: add vfio-mdev-pci driver > > On Tue, 7 Jan 2020 20:01:48 +0800 > Liu Yi L <yi.l.liu@xxxxxxxxx> wrote: > > > This patch adds sample driver named vfio-mdev-pci. It is to wrap > > a PCI device as a mediated device. For a pci device, once bound > > to vfio-mdev-pci driver, user space access of this device will > > go through vfio mdev framework. The usage of the device follows > > mdev management method. e.g. user should create a mdev before > > exposing the device to user-space. > > > > Benefit of this new driver would be acting as a sample driver > > for recent changes from "vfio/mdev: IOMMU aware mediated device" > > patchset. Also it could be a good experiment driver for future > > device specific mdev migration support. This sample driver only > > supports singleton iommu groups, for non-singleton iommu groups, > > this sample driver doesn't work. It will fail when trying to assign > > the non-singleton iommu group to VMs. > > > > To use this driver: > > a) build and load vfio-mdev-pci.ko module > > execute "make menuconfig" and config CONFIG_SAMPLE_VFIO_MDEV_PCI > > then load it with following command: > > > sudo modprobe vfio > > > sudo modprobe vfio-pci > > > sudo insmod samples/vfio-mdev-pci/vfio-mdev-pci.ko > > > > b) unbind original device driver > > e.g. use following command to unbind its original driver > > > echo $dev_bdf > /sys/bus/pci/devices/$dev_bdf/driver/unbind > > > > c) bind vfio-mdev-pci driver to the physical device > > > echo $vend_id $dev_id > /sys/bus/pci/drivers/vfio-mdev-pci/new_id > > > > d) check the supported mdev instances > > > ls /sys/bus/pci/devices/$dev_bdf/mdev_supported_types/ > > vfio-mdev-pci-type_name > > > ls /sys/bus/pci/devices/$dev_bdf/mdev_supported_types/\ > > vfio-mdev-pci-type_name/ > > available_instances create device_api devices name > > > > e) create mdev on this physical device (only 1 instance) > > > echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1003" > \ > > /sys/bus/pci/devices/$dev_bdf/mdev_supported_types/\ > > vfio-mdev-pci-type_name/create > > > > f) passthru the mdev to guest > > add the following line in QEMU boot command > > -device vfio-pci,\ > > sysfsdev=/sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1003 > > > > g) destroy mdev > > > echo 1 > /sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1003/\ > > remove > > I think much/most of those instructions should go (additionally) into > the sample driver source. yes, it would be helpful to add it in a doc. > Otherwise, it's not clear to the reader why > they should wrap the device in mdev instead of simply using a normal > vfio-pci device. Actually, the reason of wrapping device in mdev instead of simply using a normal vfio-pci is to let vendor specific driver to intercept some device access which is not allowed in vfio-pci usage. We only have PCI config space access intercepted and some other special accesses intercepted in vfio-pci. While for some vendor specific handling, it would be nice to have a way to let vendor specific driver intercept in. mdev allows it. And back to the purpose of introducing this sample driver, it is supposed to test IOMMU-capable mdev. We don't have real hardware on market, there is no way to test the VFIO extensions for IOMMU-capable mdev. Wrapping a PCI device in mdev can test the VFIO extensions well as it has hardware enforce DMA isolation. Thus makes it possible to test the extensions in VFIO. > > > > > Cc: Kevin Tian <kevin.tian@xxxxxxxxx> > > Cc: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> > > Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> > > Suggested-by: Alex Williamson <alex.williamson@xxxxxxxxxx> > > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx> > > --- > > samples/Kconfig | 10 + > > samples/Makefile | 1 + > > samples/vfio-mdev-pci/Makefile | 4 + > > samples/vfio-mdev-pci/vfio_mdev_pci.c | 397 > ++++++++++++++++++++++++++++++++++ > > 4 files changed, 412 insertions(+) > > create mode 100644 samples/vfio-mdev-pci/Makefile > > create mode 100644 samples/vfio-mdev-pci/vfio_mdev_pci.c > > > > diff --git a/samples/Kconfig b/samples/Kconfig > > index 9d236c3..50d207c 100644 > > --- a/samples/Kconfig > > +++ b/samples/Kconfig > > @@ -190,5 +190,15 @@ config SAMPLE_INTEL_MEI > > help > > Build a sample program to work with mei device. > > > > +config SAMPLE_VFIO_MDEV_PCI > > + tristate "Sample driver for wrapping PCI device as a mdev" > > + select VFIO_PCI_COMMON > > + select VFIO_PCI > > Why does this still need to select VFIO_PCI? Shouldn't all needed > infrastructure rather be covered by VFIO_PCI_COMMON already? VFIO_PCI_COMMON is supposed to be the dependency of both VFIO_PCI and SAMPLE_VFIO_MDEV_PCI. However, the source code of VFIO_PCI_COMMON are under drivers/vfio/pci which is compiled per the configuration of VFIO_PCI. Besides of letting SAMPLE_VFIO_MDEV_PCI select VFIO_PCI, I can also add a line in drivers/vfio/Makefile to make the source code under drivers/vfio/pci to be compiled when either VFIO_PCI or VFIO_PCI_COMMON are configed. But I'm afraid it is a bit ugly. So I choose to let SAMPLE_VFIO_MDEV_PCI select VFIO_PCI. If you have other idea, I would be pleased to know it. :-) > > > + depends on VFIO_MDEV && VFIO_MDEV_DEVICE > > VFIO_MDEV_DEVICE already depends on VFIO_MDEV. But maybe also make this > depend on PCI? > > > + help > > + Sample driver for wrapping a PCI device as a mdev. Once bound to > > + this driver, device passthru should through mdev path. > > "A PCI device bound to this driver will be assigned through the > mediated device framework." > > ? Maybe I should have mentioned it as "A PCI device bound to this sample driver should follow the passthru steps for mdevs as showed in Documentation/driver-api/vfio-mediated-device.rst." Does it make more sense? Thanks, Yi Liu > > > + > > + If you don't know what to do here, say N. > > > > endif # SAMPLES
