| Message ID | 20240715-sriov-v5-0-3f5539093ffc@daynix.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | virtio-net: add support for SR-IOV emulation | expand |
On Mon, Jul 15, 2024 at 02:19:06PM +0900, Akihiko Odaki wrote: > Based-on: <20240714-rombar-v2-0-af1504ef55de@daynix.com> > ("[PATCH v2 0/4] hw/pci: Convert rom_bar into OnOffAuto") OK I will revert this for now. We'll try again after the release, there will be time to address s390.
On 2024/07/30 20:37, Michael S. Tsirkin wrote: > On Mon, Jul 15, 2024 at 02:19:06PM +0900, Akihiko Odaki wrote: >> Based-on: <20240714-rombar-v2-0-af1504ef55de@daynix.com> >> ("[PATCH v2 0/4] hw/pci: Convert rom_bar into OnOffAuto") > > OK I will revert this for now. We'll try again after the release, > there will be time to address s390. > I'd like to know if anybody wants to use igb on a s390x machine configured with libvirt. Such a configuration is already kind of broken, and it is likely to require significant effort on both side of libvirt and QEMU to fix it. As an alternative, I'm also introducing SR-IOV support to virtio-net-pci. It does not suffer the same problem with igb thanks to its flexible configuration mechanism. Regards, Akihiko Odaki
On Tue, Jul 30, 2024 at 09:26:20PM +0900, Akihiko Odaki wrote: > On 2024/07/30 20:37, Michael S. Tsirkin wrote: > > On Mon, Jul 15, 2024 at 02:19:06PM +0900, Akihiko Odaki wrote: > > > Based-on: <20240714-rombar-v2-0-af1504ef55de@daynix.com> > > > ("[PATCH v2 0/4] hw/pci: Convert rom_bar into OnOffAuto") > > > > OK I will revert this for now. We'll try again after the release, > > there will be time to address s390. > > > > I'd like to know if anybody wants to use igb on a s390x machine configured > with libvirt. Such a configuration is already kind of broken, and it is > likely to require significant effort on both side of libvirt and QEMU to fix > it. I assume Cédric wouldn't report it if was unused. > As an alternative, I'm also introducing SR-IOV support to virtio-net-pci. It > does not suffer the same problem with igb thanks to its flexible > configuration mechanism. > > Regards, > Akihiko Odaki Sounds like this needs more review time, anyway.
On 7/30/24 19:56, Michael S. Tsirkin wrote: > On Tue, Jul 30, 2024 at 09:26:20PM +0900, Akihiko Odaki wrote: >> On 2024/07/30 20:37, Michael S. Tsirkin wrote: >>> On Mon, Jul 15, 2024 at 02:19:06PM +0900, Akihiko Odaki wrote: >>>> Based-on: <20240714-rombar-v2-0-af1504ef55de@daynix.com> >>>> ("[PATCH v2 0/4] hw/pci: Convert rom_bar into OnOffAuto") >>> >>> OK I will revert this for now. We'll try again after the release, >>> there will be time to address s390. >>> >> >> I'd like to know if anybody wants to use igb on a s390x machine configured >> with libvirt. Such a configuration is already kind of broken, and it is >> likely to require significant effort on both side of libvirt and QEMU to fix >> it. > > > I assume Cédric wouldn't report it if was unused. > > >> As an alternative, I'm also introducing SR-IOV support to virtio-net-pci. It >> does not suffer the same problem with igb thanks to its flexible >> configuration mechanism. >> >> Regards, >> Akihiko Odaki > > Sounds like this needs more review time, anyway. > > Using an emulated IGB device in a s390x VM is not a common scenario. The IGB device is not supported downstream (RHEL on Z). However, the change broke the s390x machines I use for upstream QEMU development, I removed the IGB device as a fix for now. The Z PCI device model has 'uid' and 'fid' properties which are set by the VMM, and in this case, they are auto-generated, hence the conflicting ids with libvirt. This is Z specific but, possibly there are subtle use cases on other platforms which could have similar consequences. Something to be aware of. Also, and this is why I thought it was important to report. Creating PCI devices at machine init time (with -nodefaults) in the back of the management layer is a no-no. libvirt requests to have full control on the machine topology and this change seems like a violation of this rule, even if VFs are kind of special. Daniel, did I understand correctly the above constraint on the machine definition ? I can't say if we should revert for 9.1. Again, this Z is specific. The changes were introduced to catch errors early when the PF device is realized. There is no doubt they are useful. Some rework is needed to avoid the conflicting id issue though. Thanks, C.
On 2024/07/31 17:58, Cédric Le Goater wrote: > On 7/30/24 19:56, Michael S. Tsirkin wrote: >> On Tue, Jul 30, 2024 at 09:26:20PM +0900, Akihiko Odaki wrote: >>> On 2024/07/30 20:37, Michael S. Tsirkin wrote: >>>> On Mon, Jul 15, 2024 at 02:19:06PM +0900, Akihiko Odaki wrote: >>>>> Based-on: <20240714-rombar-v2-0-af1504ef55de@daynix.com> >>>>> ("[PATCH v2 0/4] hw/pci: Convert rom_bar into OnOffAuto") >>>> >>>> OK I will revert this for now. We'll try again after the release, >>>> there will be time to address s390. >>>> >>> >>> I'd like to know if anybody wants to use igb on a s390x machine >>> configured >>> with libvirt. Such a configuration is already kind of broken, and it is >>> likely to require significant effort on both side of libvirt and QEMU >>> to fix >>> it. >> >> >> I assume Cédric wouldn't report it if was unused. >> >> >>> As an alternative, I'm also introducing SR-IOV support to >>> virtio-net-pci. It >>> does not suffer the same problem with igb thanks to its flexible >>> configuration mechanism. >>> >>> Regards, >>> Akihiko Odaki >> >> Sounds like this needs more review time, anyway. >> >> > > Using an emulated IGB device in a s390x VM is not a common scenario. > The IGB device is not supported downstream (RHEL on Z). However, the > change broke the s390x machines I use for upstream QEMU development, > I removed the IGB device as a fix for now. > > The Z PCI device model has 'uid' and 'fid' properties which are set > by the VMM, and in this case, they are auto-generated, hence the > conflicting ids with libvirt. This is Z specific but, possibly there > are subtle use cases on other platforms which could have similar > consequences. Something to be aware of. > > > Also, and this is why I thought it was important to report. Creating > PCI devices at machine init time (with -nodefaults) in the back of the > management layer is a no-no. libvirt requests to have full control > on the machine topology and this change seems like a violation of > this rule, even if VFs are kind of special. > > Daniel, did I understand correctly the above constraint on the machine > definition ? It is problematic even if it is not init time. QEMU shouldn't implicitly add a PCI device without letting the management layer know. For the virtio-net SR-IOV support which I have been preparing, I'm avoiding automatically adding PCI devices but instead letting the user create VFs. However, fixing existing SR-IOV devices (igb and nvme) will require more efforts and possible breaking changes of the command line. > > > I can't say if we should revert for 9.1. Again, this Z is specific. > The changes were introduced to catch errors early when the PF device > is realized. There is no doubt they are useful. Some rework is needed > to avoid the conflicting id issue though. I think it is a good idea to revert these patches for now, and add them back along with the virtio-net-pci SR-IOV support when the next merge window starts though I don't require to do so. If someone experiences this problem in the next merge window, we can advise to use virtio-net-pci, or to specify qemu:commandline to workaround it. We can start thinking of making a breaking change if neither of them satisfies the requirement. Regards, Akihiko Odaki
On Thu, Aug 01, 2024 at 04:13:14PM +0900, Akihiko Odaki wrote:
> I think it is a good idea to revert these patches for now
OK I reverted the 2 patchsets. there were some bugfixes there
but I had to revert them too due to the dependency.
If appropriate, feel free to resubmit just the fixes.
Based-on: <20240714-rombar-v2-0-af1504ef55de@daynix.com> ("[PATCH v2 0/4] hw/pci: Convert rom_bar into OnOffAuto") Introduction ------------ This series is based on the RFC series submitted by Yui Washizu[1]. See also [2] for the context. This series enables SR-IOV emulation for virtio-net. It is useful to test SR-IOV support on the guest, or to expose several vDPA devices in a VM. vDPA devices can also provide L2 switching feature for offloading though it is out of scope to allow the guest to configure such a feature. The PF side code resides in virtio-pci. The VF side code resides in the PCI common infrastructure, but it is restricted to work only for virtio-net-pci because of lack of validation. User Interface -------------- A user can configure a SR-IOV capable virtio-net device by adding virtio-net-pci functions to a bus. Below is a command line example: -netdev user,id=n -netdev user,id=o -netdev user,id=p -netdev user,id=q -device pcie-root-port,id=b -device virtio-net-pci,bus=b,addr=0x0.0x3,netdev=q,sriov-pf=f -device virtio-net-pci,bus=b,addr=0x0.0x2,netdev=p,sriov-pf=f -device virtio-net-pci,bus=b,addr=0x0.0x1,netdev=o,sriov-pf=f -device virtio-net-pci,bus=b,addr=0x0.0x0,netdev=n,id=f The VFs specify the paired PF with "sriov-pf" property. The PF must be added after all VFs. It is user's responsibility to ensure that VFs have function numbers larger than one of the PF, and the function numbers have a consistent stride. Keeping VF instances -------------------- A problem with SR-IOV emulation is that it needs to hotplug the VFs as the guest requests. Previously, this behavior was implemented by realizing and unrealizing VFs at runtime. However, this strategy does not work well for the proposed virtio-net emulation; in this proposal, device options passed in the command line must be maintained as VFs are hotplugged, but they are consumed when the machine starts and not available after that, which makes realizing VFs at runtime impossible. As an strategy alternative to runtime realization/unrealization, this series proposes to reuse the code to power down PCI Express devices. When a PCI Express device is powered down, it will be hidden from the guest but will be kept realized. This effectively implements the behavior we need for the SR-IOV emulation. Summary ------- Patch 1 disables ROM BAR, which virtio-net-pci enables by default, for VFs. Patch 2 makes zero stride valid for 1 VF configuration. Patch 3 and 4 adds validations. Patch 5 adds user-created SR-IOV VF infrastructure. Patch 6 makes virtio-pci work as SR-IOV PF for user-created VFs. Patch 7 allows user to create SR-IOV VFs with virtio-net-pci. [1] https://patchew.org/QEMU/1689731808-3009-1-git-send-email-yui.washidu@gmail.com/ [2] https://lore.kernel.org/all/5d46f455-f530-4e5e-9ae7-13a2297d4bc5@daynix.com/ Co-developed-by: Yui Washizu <yui.washidu@gmail.com> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com> --- Changes in v5: - Dropped the RFC tag. - Fixed device unrealization. - Rebased. - Link to v4: https://lore.kernel.org/r/20240428-sriov-v4-0-ac8ac6212982@daynix.com Changes in v4: - Added patch "hw/pci: Fix SR-IOV VF number calculation" to fix division by zero reported by Yui Washizu. - Rebased. - Link to v3: https://lore.kernel.org/r/20240305-sriov-v3-0-abdb75770372@daynix.com Changes in v3: - Rebased. - Link to v2: https://lore.kernel.org/r/20231210-sriov-v2-0-b959e8a6dfaf@daynix.com Changes in v2: - Changed to keep VF instances. - Link to v1: https://lore.kernel.org/r/20231202-sriov-v1-0-32b3570f7bd6@daynix.com --- Akihiko Odaki (8): hw/pci: Do not add ROM BAR for SR-IOV VF hw/pci: Fix SR-IOV VF number calculation pcie_sriov: Ensure PF and VF are mutually exclusive pcie_sriov: Check PCI Express for SR-IOV PF pcie_sriov: Allow user to create SR-IOV device virtio-pci: Implement SR-IOV PF virtio-net: Implement SR-IOV VF docs: Document composable SR-IOV device MAINTAINERS | 1 + docs/system/index.rst | 1 + docs/system/sriov.rst | 36 +++++ include/hw/pci/pci_device.h | 6 +- include/hw/pci/pcie_sriov.h | 18 +++ include/hw/virtio/virtio-pci.h | 1 + hw/pci/pci.c | 76 +++++++---- hw/pci/pcie_sriov.c | 298 +++++++++++++++++++++++++++++++++-------- hw/virtio/virtio-net-pci.c | 1 + hw/virtio/virtio-pci.c | 20 ++- 10 files changed, 369 insertions(+), 89 deletions(-) --- base-commit: e7b8390b9167be9272c2c959919d9b397842da7f change-id: 20231202-sriov-9402fb262be8 Best regards,