On Thu, Dec 14, 2023 at 11:03:49AM +0200, Yishai Hadas wrote: > On 14/12/2023 8:38, Michael S. Tsirkin wrote: > > On Thu, Dec 07, 2023 at 12:28:20PM +0200, Yishai Hadas wrote: > > > Introduce a vfio driver over virtio devices to support the legacy > > > interface functionality for VFs. > > > > > > Background, from the virtio spec [1]. > > > -------------------------------------------------------------------- > > > In some systems, there is a need to support a virtio legacy driver with > > > a device that does not directly support the legacy interface. In such > > > scenarios, a group owner device can provide the legacy interface > > > functionality for the group member devices. The driver of the owner > > > device can then access the legacy interface of a member device on behalf > > > of the legacy member device driver. > > > > > > For example, with the SR-IOV group type, group members (VFs) can not > > > present the legacy interface in an I/O BAR in BAR0 as expected by the > > > legacy pci driver. If the legacy driver is running inside a virtual > > > machine, the hypervisor executing the virtual machine can present a > > > virtual device with an I/O BAR in BAR0. The hypervisor intercepts the > > > legacy driver accesses to this I/O BAR and forwards them to the group > > > owner device (PF) using group administration commands. > > > -------------------------------------------------------------------- > > > > > > Specifically, this driver adds support for a virtio-net VF to be exposed > > > as a transitional device to a guest driver and allows the legacy IO BAR > > > functionality on top. > > > > > > This allows a VM which uses a legacy virtio-net driver in the guest to > > > work transparently over a VF which its driver in the host is that new > > > driver. > > > > > > The driver can be extended easily to support some other types of virtio > > > devices (e.g virtio-blk), by adding in a few places the specific type > > > properties as was done for virtio-net. > > > > > > For now, only the virtio-net use case was tested and as such we introduce > > > the support only for such a device. > > > > > > Practically, > > > Upon probing a VF for a virtio-net device, in case its PF supports > > > legacy access over the virtio admin commands and the VF doesn't have BAR > > > 0, we set some specific 'vfio_device_ops' to be able to simulate in SW a > > > transitional device with I/O BAR in BAR 0. > > > > > > The existence of the simulated I/O bar is reported later on by > > > overwriting the VFIO_DEVICE_GET_REGION_INFO command and the device > > > exposes itself as a transitional device by overwriting some properties > > > upon reading its config space. > > > > > > Once we report the existence of I/O BAR as BAR 0 a legacy driver in the > > > guest may use it via read/write calls according to the virtio > > > specification. > > > > > > Any read/write towards the control parts of the BAR will be captured by > > > the new driver and will be translated into admin commands towards the > > > device. > > > > > > Any data path read/write access (i.e. virtio driver notifications) will > > > be forwarded to the physical BAR which its properties were supplied by > > > the admin command VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO upon the > > > probing/init flow. > > > > > > With that code in place a legacy driver in the guest has the look and > > > feel as if having a transitional device with legacy support for both its > > > control and data path flows. > > > > > > [1] > > > https://github.com/oasis-tcs/virtio-spec/commit/03c2d32e5093ca9f2a17797242fbef88efe94b8c > > > > > > Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > > > Signed-off-by: Yishai Hadas <yishaih@xxxxxxxxxx> > > > --- > > > MAINTAINERS | 7 + > > > drivers/vfio/pci/Kconfig | 2 + > > > drivers/vfio/pci/Makefile | 2 + > > > drivers/vfio/pci/virtio/Kconfig | 16 + > > > drivers/vfio/pci/virtio/Makefile | 4 + > > > drivers/vfio/pci/virtio/main.c | 567 +++++++++++++++++++++++++++++++ > > > 6 files changed, 598 insertions(+) > > > create mode 100644 drivers/vfio/pci/virtio/Kconfig > > > create mode 100644 drivers/vfio/pci/virtio/Makefile > > > create mode 100644 drivers/vfio/pci/virtio/main.c > > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > > index 012df8ccf34e..b246b769092d 100644 > > > --- a/MAINTAINERS > > > +++ b/MAINTAINERS > > > @@ -22872,6 +22872,13 @@ L: kvm@xxxxxxxxxxxxxxx > > > S: Maintained > > > F: drivers/vfio/pci/mlx5/ > > > +VFIO VIRTIO PCI DRIVER > > > +M: Yishai Hadas <yishaih@xxxxxxxxxx> > > > +L: kvm@xxxxxxxxxxxxxxx > > > +L: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx > > > +S: Maintained > > > +F: drivers/vfio/pci/virtio > > > + > > > VFIO PCI DEVICE SPECIFIC DRIVERS > > > R: Jason Gunthorpe <jgg@xxxxxxxxxx> > > > R: Yishai Hadas <yishaih@xxxxxxxxxx> > > > diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig > > > index 8125e5f37832..18c397df566d 100644 > > > --- a/drivers/vfio/pci/Kconfig > > > +++ b/drivers/vfio/pci/Kconfig > > > @@ -65,4 +65,6 @@ source "drivers/vfio/pci/hisilicon/Kconfig" > > > source "drivers/vfio/pci/pds/Kconfig" > > > +source "drivers/vfio/pci/virtio/Kconfig" > > > + > > > endmenu > > > diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile > > > index 45167be462d8..046139a4eca5 100644 > > > --- a/drivers/vfio/pci/Makefile > > > +++ b/drivers/vfio/pci/Makefile > > > @@ -13,3 +13,5 @@ obj-$(CONFIG_MLX5_VFIO_PCI) += mlx5/ > > > obj-$(CONFIG_HISI_ACC_VFIO_PCI) += hisilicon/ > > > obj-$(CONFIG_PDS_VFIO_PCI) += pds/ > > > + > > > +obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio/ > > > diff --git a/drivers/vfio/pci/virtio/Kconfig b/drivers/vfio/pci/virtio/Kconfig > > > new file mode 100644 > > > index 000000000000..3a6707639220 > > > --- /dev/null > > > +++ b/drivers/vfio/pci/virtio/Kconfig > > > @@ -0,0 +1,16 @@ > > > +# SPDX-License-Identifier: GPL-2.0-only > > > +config VIRTIO_VFIO_PCI > > > + tristate "VFIO support for VIRTIO NET PCI devices" > > > + depends on VIRTIO_PCI > > > + select VFIO_PCI_CORE > > > + help > > > + This provides support for exposing VIRTIO NET VF devices which support > > > + legacy IO access, using the VFIO framework that can work with a legacy > > > + virtio driver in the guest. > > > + Based on PCIe spec, VFs do not support I/O Space; thus, VF BARs shall > > > + not indicate I/O Space. > > > + As of that this driver emulated I/O BAR in software to let a VF be > > > + seen as a transitional device in the guest and let it work with > > > + a legacy driver. > > > + > > > + If you don't know what to do here, say N. > > > > BTW shouldn't this driver be limited to X86? Things like lack of memory > > barriers will make legacy virtio racy on e.g. ARM will they not? > > And endian-ness will be broken on PPC ... > > > > OK, if so, we can come with the below extra code. > Makes sense ? > > I'll squash it as part of V8 to the relevant patch. > > diff --git a/drivers/virtio/virtio_pci_modern.c > b/drivers/virtio/virtio_pci_modern.c > index 37a0035f8381..b652e91b9df4 100644 > --- a/drivers/virtio/virtio_pci_modern.c > +++ b/drivers/virtio/virtio_pci_modern.c > @@ -794,6 +794,9 @@ bool virtio_pci_admin_has_legacy_io(struct pci_dev > *pdev) > struct virtio_device *virtio_dev = virtio_pci_vf_get_pf_dev(pdev); > struct virtio_pci_device *vp_dev; > > +#ifndef CONFIG_X86 > + return false; > +#endif > if (!virtio_dev) > return false; > > Yishai Isn't there going to be a bunch more dead code that compiler won't be able to elide? -- MST
