Changes from previous version [1], all of them result of feedback from Alex Williamson and Abdulla Bubshait: - use <address type='none'/> instead of creating a new subsys attribute; - expand the change to all PCI hostdevs. Former patch 01 was discarded because we don't need the PCI Multifunction helpers for now; - series changed name to reflect what it's being done - new patch 04: add documentation to formatdomain.html.in To avoid a huge wall of text please refer to [1] for context about the road up to here. Commit msgs of the first 3 patches tells the story as well. [1] https://www.redhat.com/archives/libvir-list/2019-October/msg00298.html What I want to discuss here instead is a caveat that I've found while testing this work, since its first version. This test was done in a Power 8 system with a Broadcom BCM5719 PCIe Multifunction card, with 4 virtual functions. This series enables Libvirt to declare PCI hostdevs that will not be visible to the guest using address type='none'. During the tests I faced a scenario that I expected to fail, but it didn't. This is the relevant XML except: <hostdev mode='subsystem' type='pci' managed='yes'> <driver name='vfio'/> <source> <address domain='0x0001' bus='0x09' slot='0x00' function='0x0'/> </source> <address type='none'/> </hostdev> <hostdev mode='subsystem' type='pci' managed='yes'> <driver name='vfio'/> <source> <address domain='0x0001' bus='0x09' slot='0x00' function='0x1'/> </source> <address type='none'/> </hostdev> <hostdev mode='subsystem' type='pci' managed='yes'> <driver name='vfio'/> <source> <address domain='0x0001' bus='0x09' slot='0x00' function='0x2'/> </source> <address type='pci' domain='0x0000' bus='0x01' slot='0x01' function='0x2'/> </hostdev> <hostdev mode='subsystem' type='pci' managed='yes'> <driver name='vfio'/> <source> <address domain='0x0001' bus='0x09' slot='0x00' function='0x3'/> </source> <address type='none'/> </hostdev> I'm declaring all the BCM5719 functions in the XML, but I am making functions 0, 1 and 3 unassignable by the guest using address type='none'. This test was meant to fail, but it didn't. To my surprise the guest booted and the device is functional: $ lspci 0000:00:01.0 Unclassified device [00ff]: Red Hat, Inc Virtio memory balloon 0000:00:03.0 USB controller: Red Hat, Inc. QEMU XHCI Host Controller (rev 01) 0000:00:04.0 SCSI storage controller: Red Hat, Inc Virtio block device 0001:00:01.2 Ethernet controller: Broadcom Limited NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01) $ I've talked with Michael Roth (QEMU PPC64 developer that worked with the PCI multifunction hotplug/unplug support in the PPC64 machine) about this. He mentioned that this is intended. I'll quote here what he had to say about it: "The current logic is that we only emit the hotplug event when function 0 is attached, but if some other function is attached at boot-time the guest will still see it on the bus, and whether that works or not I think is up to the device/driver" This explains why this test didn't fail as I expected. At least for the PPC64 machine, depending on the device support, this setup is allowed. PPC64 machine uses function 0 hotplug as a signal of 'plug all the queue functions and function 0', but function 0 isn't required at boot time. I would like to hear other opinions in this because I can't say whether this is allowed in x86. I am mentioning all this now because this had a direct impact on the design of this work since the previous version, and I failed to bring it up back then. I am *not* checking for the assignment of function 0 at guest boot time in Libvirt, leaving the user free to decide what to do. I am aware that this will be inconsistent to the logic of the PCI multifunction hotplug/unplug support, where function 0 is required. This also puts a lot of faith in the user, relying that the user is fully aware of the capabilities of the hardware. My question is: should Libvirt force function 0 to be present in boot time as well, regardless of whether the PPC64 guest or some cards are able to boot without it? Thanks, DHB Daniel Henrique Barboza (4): domain_conf: allow address type='none' to unassign PCI hostdevs qemu: handle unassigned PCI hostdevs in command line and alias virhostdev.c: check all IOMMU devs in virHostdevPreparePCIDevices formatdomain.html.in: document <address type='none'/> docs/formatdomain.html.in | 15 +++++ docs/schemas/domaincommon.rng | 5 ++ src/conf/domain_conf.c | 56 ++++++++++++++-- src/conf/domain_conf.h | 3 + src/qemu/qemu_alias.c | 6 ++ src/qemu/qemu_command.c | 4 ++ src/qemu/qemu_domain_address.c | 6 ++ src/util/virhostdev.c | 64 +++++++++++++++++-- .../hostdev-pci-address-none.args | 31 +++++++++ .../hostdev-pci-address-none.xml | 42 ++++++++++++ ...ostdev-pci-multifunction-partial-fail.args | 31 +++++++++ ...hostdev-pci-multifunction-partial-fail.xml | 35 ++++++++++ tests/qemuxml2argvtest.c | 8 +++ .../hostdev-pci-address-none.xml | 58 +++++++++++++++++ tests/qemuxml2xmltest.c | 1 + 15 files changed, 352 insertions(+), 13 deletions(-) create mode 100644 tests/qemuxml2argvdata/hostdev-pci-address-none.args create mode 100644 tests/qemuxml2argvdata/hostdev-pci-address-none.xml create mode 100644 tests/qemuxml2argvdata/hostdev-pci-multifunction-partial-fail.args create mode 100644 tests/qemuxml2argvdata/hostdev-pci-multifunction-partial-fail.xml create mode 100644 tests/qemuxml2xmloutdata/hostdev-pci-address-none.xml -- 2.21.0 -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
