On Thu, Dec 05, 2019 at 02:33:19PM +0800, Jason Wang wrote: > Hi: > > On 2019/12/5 上午11:24, Yan Zhao wrote: > > For SRIOV devices, VFs are passthroughed into guest directly without host > > driver mediation. However, when VMs migrating with passthroughed VFs, > > dynamic host mediation is required to (1) get device states, (2) get > > dirty pages. Since device states as well as other critical information > > required for dirty page tracking for VFs are usually retrieved from PFs, > > it is handy to provide an extension in PF driver to centralizingly control > > VFs' migration. > > > > Therefore, in order to realize (1) passthrough VFs at normal time, (2) > > dynamically trap VFs' bars for dirty page tracking and > > > A silly question, what's the reason for doing this, is this a must for dirty > page tracking? > For performance consideration. VFs' bars should be passthoughed at normal time and only enter into trap state on need. > > > (3) centralizing > > VF critical states retrieving and VF controls into one driver, we propose > > to introduce mediate ops on top of current vfio-pci device driver. > > > > > > _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ > > __________ register mediate ops| ___________ ___________ | > > | |<-----------------------| VF | | | > > | vfio-pci | | | mediate | | PF driver | | > > |__________|----------------------->| driver | |___________| > > | open(pdev) | ----------- | | > > | | > > | |_ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _| > > \|/ \|/ > > ----------- ------------ > > | VF | | PF | > > ----------- ------------ > > > > > > VF mediate driver could be a standalone driver that does not bind to > > any devices (as in demo code in patches 5-6) or it could be a built-in > > extension of PF driver (as in patches 7-9) . > > > > Rather than directly bind to VF, VF mediate driver register a mediate > > ops into vfio-pci in driver init. vfio-pci maintains a list of such > > mediate ops. > > (Note that: VF mediate driver can register mediate ops into vfio-pci > > before vfio-pci binding to any devices. And VF mediate driver can > > support mediating multiple devices.) > > > > When opening a device (e.g. a VF), vfio-pci goes through the mediate ops > > list and calls each vfio_pci_mediate_ops->open() with pdev of the opening > > device as a parameter. > > VF mediate driver should return success or failure depending on it > > supports the pdev or not. > > E.g. VF mediate driver would compare its supported VF devfn with the > > devfn of the passed-in pdev. > > Once vfio-pci finds a successful vfio_pci_mediate_ops->open(), it will > > stop querying other mediate ops and bind the opening device with this > > mediate ops using the returned mediate handle. > > > > Further vfio-pci ops (VFIO_DEVICE_GET_REGION_INFO ioctl, rw, mmap) on the > > VF will be intercepted into VF mediate driver as > > vfio_pci_mediate_ops->get_region_info(), > > vfio_pci_mediate_ops->rw, > > vfio_pci_mediate_ops->mmap, and get customized. > > For vfio_pci_mediate_ops->rw and vfio_pci_mediate_ops->mmap, they will > > further return 'pt' to indicate whether vfio-pci should further > > passthrough data to hw. > > > > when vfio-pci closes the VF, it calls its vfio_pci_mediate_ops->release() > > with a mediate handle as parameter. > > > > The mediate handle returned from vfio_pci_mediate_ops->open() lets VF > > mediate driver be able to differentiate two opening VFs of the same device > > id and vendor id. > > > > When VF mediate driver exits, it unregisters its mediate ops from > > vfio-pci. > > > > > > In this patchset, we enable vfio-pci to provide 3 things: > > (1) calling mediate ops to allow vendor driver customizing default > > region info/rw/mmap of a region. > > (2) provide a migration region to support migration > > > What's the benefit of introducing a region? It looks to me we don't expect > the region to be accessed directly from guest. Could we simply extend device > fd ioctl for doing such things? > You may take a look on mdev live migration discussions in https://lists.gnu.org/archive/html/qemu-devel/2019-11/msg01763.html or previous discussion at https://lists.gnu.org/archive/html/qemu-devel/2019-02/msg04908.html, which has kernel side implemetation https://patchwork.freedesktop.org/series/56876/ generaly speaking, qemu part of live migration is consistent for vfio-pci + mediate ops way or mdev way. The region is only a channel for QEMU and kernel to communicate information without introducing IOCTLs. > > > (3) provide a dynamic trap bar info region to allow vendor driver > > control trap/untrap of device pci bars > > > > This vfio-pci + mediate ops way differs from mdev way in that > > (1) medv way needs to create a 1:1 mdev device on top of one VF, device > > specific mdev parent driver is bound to VF directly. > > (2) vfio-pci + mediate ops way does not create mdev devices and VF > > mediate driver does not bind to VFs. Instead, vfio-pci binds to VFs. > > > > The reason why we don't choose the way of writing mdev parent driver is > > that > > (1) VFs are almost all the time directly passthroughed. Directly binding > > to vfio-pci can make most of the code shared/reused. > > > Can we split out the common parts from vfio-pci? > That's very attractive. but one cannot implement a vfio-pci except export everything in it as common part :) > > > If we write a > > vendor specific mdev parent driver, most of the code (like passthrough > > style of rw/mmap) still needs to be copied from vfio-pci driver, which is > > actually a duplicated and tedious work. > > > The mediate ops looks quite similar to what vfio-mdev did. And it looks to > me we need to consider live migration for mdev as well. In that case, do we > still expect mediate ops through VFIO directly? > > > > (2) For features like dynamically trap/untrap pci bars, if they are in > > vfio-pci, they can be available to most people without repeated code > > copying and re-testing. > > (3) with a 1:1 mdev driver which passthrough VFs most of the time, people > > have to decide whether to bind VFs to vfio-pci or mdev parent driver before > > it runs into a real migration need. However, if vfio-pci is bound > > initially, they have no chance to do live migration when there's a need > > later. > > > We can teach management layer to do this. > No. not possible as vfio-pci by default has no migration region and dirty page tracking needs vendor's mediation at least for most passthrough devices now. Thanks Yn > Thanks > > > > > > In this patchset, > > - patches 1-4 enable vfio-pci to call mediate ops registered by vendor > > driver to mediate/customize region info/rw/mmap. > > > > - patches 5-6 provide a standalone sample driver to register a mediate ops > > for Intel Graphics Devices. It does not bind to IGDs directly but decides > > what devices it supports via its pciidlist. It also demonstrates how to > > dynamic trap a device's PCI bars. (by adding more pciids in its > > pciidlist, this sample driver actually is not necessarily limited to > > support IGDs) > > > > - patch 7-9 provide a sample on i40e driver that supports Intel(R) > > Ethernet Controller XL710 Family of devices. It supports VF precopy live > > migration on Intel's 710 SRIOV. (but we commented out the real > > implementation of dirty page tracking and device state retrieving part > > to focus on demonstrating framework part. Will send out them in future > > versions) > > patch 7 registers/unregisters VF mediate ops when PF driver > > probes/removes. It specifies its supporting VFs via > > vfio_pci_mediate_ops->open(pdev) > > > > patch 8 reports device cap of VFIO_PCI_DEVICE_CAP_MIGRATION and > > provides a sample implementation of migration region. > > The QEMU part of vfio migration is based on v8 > > https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg05542.html. > > We do not based on recent v9 because we think there are still opens in > > dirty page track part in that series. > > > > patch 9 reports device cap of VFIO_PCI_DEVICE_CAP_DYNAMIC_TRAP_BAR and > > provides an example on how to trap part of bar0 when migration starts > > and passthrough this part of bar0 again when migration fails. > > > > Yan Zhao (9): > > vfio/pci: introduce mediate ops to intercept vfio-pci ops > > vfio/pci: test existence before calling region->ops > > vfio/pci: register a default migration region > > vfio-pci: register default dynamic-trap-bar-info region > > samples/vfio-pci/igd_dt: sample driver to mediate a passthrough IGD > > sample/vfio-pci/igd_dt: dynamically trap/untrap subregion of IGD bar0 > > i40e/vf_migration: register mediate_ops to vfio-pci > > i40e/vf_migration: mediate migration region > > i40e/vf_migration: support dynamic trap of bar0 > > > > drivers/net/ethernet/intel/Kconfig | 2 +- > > drivers/net/ethernet/intel/i40e/Makefile | 3 +- > > drivers/net/ethernet/intel/i40e/i40e.h | 2 + > > drivers/net/ethernet/intel/i40e/i40e_main.c | 3 + > > .../ethernet/intel/i40e/i40e_vf_migration.c | 626 ++++++++++++++++++ > > .../ethernet/intel/i40e/i40e_vf_migration.h | 78 +++ > > drivers/vfio/pci/vfio_pci.c | 189 +++++- > > drivers/vfio/pci/vfio_pci_private.h | 2 + > > include/linux/vfio.h | 18 + > > include/uapi/linux/vfio.h | 160 +++++ > > samples/Kconfig | 6 + > > samples/Makefile | 1 + > > samples/vfio-pci/Makefile | 2 + > > samples/vfio-pci/igd_dt.c | 367 ++++++++++ > > 14 files changed, 1455 insertions(+), 4 deletions(-) > > create mode 100644 drivers/net/ethernet/intel/i40e/i40e_vf_migration.c > > create mode 100644 drivers/net/ethernet/intel/i40e/i40e_vf_migration.h > > create mode 100644 samples/vfio-pci/Makefile > > create mode 100644 samples/vfio-pci/igd_dt.c > > > -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
