On Tue, Mar 08, 2022 at 09:57:04PM +0530, Ani Sinha wrote: > > > On Tue, Mar 8, 2022 at 21:21 Laine Stump <la...@redhat.com> wrote: > > Aha! the domain of qemu-devel@nongnu.org was incorrect in the original > send (it was "nognu.org"), so none of this thread was making it to that > list. I've corrected it in this message, but interested parties from > qemu-devel will need to look on the libvir-list archives for the actual > patch mails: > > https://listman.redhat.com/archives/libvir-list/2022-March/229089.html > > Anyone else who responds to any of the mail on this thread should fix > the qemu-devel address accordingly. > > > This patch set has been a true test of my diligence and perseverance 🙂
Right. But could you maybe repost to the proper qemu-devel? I'd like to be able to pull the whole email not just the summary listman deems safe to show me. > > > > On 3/8/22 10:33 AM, Laine Stump wrote: > > On 3/8/22 1:39 AM, Ani Sinha wrote: > >> Changelog: > >> v2 - rebased the patch series to latest master. > >> > >> I am re-introducing the patchset for <acpi-hotplug-bridge> which got > >> reverted here few months back: > >> > >> https://www.spinics.net/linux/fedora/libvir/msg224089.html > >> > >> The reason for the reversal was that there seemed to be some > >> instability/issues around the use of the qemu commandline which this > >> patchset tries to support. In particular, some guest operating systems > >> did not like the way QEMU was trying to disable native hotplug on pcie > >> root ports. > > > > My memory isn't completely clear, but I think there was also the issue > > that the option claims to enable ACPI hotplug when set to on, but > > instead what it actually does (in the Q35 case at least) is to enable > > native PCI hotplug when set to off (without actually disabling ACPI > > hotplug) and disable native PCI hotplug when set to on, or something > > like that. This ends up leaving it up to the guest OS to decide which > > type of hotplug to use, meaning its decision could override what's in > > the libvirt config, thus confusing everyone. Again, I probably have the > > details mixed up, but it was something like this. > > > > I asked mst about this this morning, and he suggested something that > > you've already done - Cc'ing the series to qemu-devel and the relevant > > maintainers so we can have a discussion with all involved parties about > > their opinions on whether we really should expose this existing option > > in libvirt, or if we should instead have two new options that are more > > orthogonal about enabling/disabling the two types of hotplug, so that > > libvirt config can more accurately represent what is being presented to > > the guest rather than a "best guess" of what we think the guest is going > > to do with what is presented. > > > > (Michael did also say that, with the current flurry of bug reports for > > the QEMU rc's, this discusion may not happen until closer to release > > when the bug reports die down. I know this doesn't mesh with your desire > > to "push now to allow for testing" (which in general would be a good > > thing if we were certain that we wanted the option like this and were > > just expecting some minor bugs that could be fixed), but my opinion is > > that 1) it's possible for anyone interested to test the functionality > > using <qemu:commandline>, and 2) we should avoid turning libvirt git > > into a revolving door of experiments. The only practical difference > > between using <qemu:commandline> and having a dedicated option is that > > the use of <qemu:commandline> causes the domain to be tainted, and the > > XML is a bit more complicated. But since the people we're talking about > > here will already have built their own libvirt binaries, the tainted > > status of any guests is irrelevant and the extra complexity of using > > <qemu:commandline> is probably trivial to them :-). > > > >> Subsequently, in QEMU 6.2, we have changed our mechanism > >> using which we disable native hotplug. As I understand, we do not have > >> any reported issues so far in 6.2 around this area. QEMU will enter a > >> soft feature freeze in the first week of march in prep for 7.0 release. > >> Libvirt is also entering a new release cycle phaze. Hence, I am > >> introducing this patchset early enough in the release cycles so that if > >> we do see any issues on the qemu side during the rc0, rc1 cycles and if > >> reversal of this patchset is again required, it can be done in time > >> before the next libvirt release end of March. > >> > >> All the patches in this series had been previously reviewed. Some > >> subsequent fixes were made after my initial patches were pushed. I have > >> squashed all those fixes and consolidated them into four patches. I > have > >> also updated the documentation to reflect the new changes from the QEMU > >> side and rebased my changes fixing the tests in the process. > >> > >> What changed in QEMU post version 6.1 ? > >> ========================================= > >> > >> We have made basically two major changes in QEMU. First is this change: > >> > >> (1) commit 211afe5c69b597acf85fdd577eb497f5be1ffbd8 > >> Author: Julia Suvorova <jus...@redhat.com> > >> Date:  Fri Nov 12 06:08:56 2021 -0500 > >> > >>     hw/i386/acpi-build: Deny control on PCIe Native Hot-plug in _OSC > >>     There are two ways to enable ACPI PCI Hot-plug: > >>             * Disable the Hot-plug Capable bit on PCIe slots. > >>     This was the first approach which led to regression [1-2], as > >>     I/O space for a port is allocated only when it is hot-pluggable, > >>     which is determined by HPC bit. > >>             * Leave the HPC bit on and disable PCIe Native Hot-plug > >> in _OSC > >>               method. > >>     This removes the (future) ability of hot-plugging switches with > PCIe > >>     Native hotplug since ACPI PCI Hot-plug only works with > cold-plugged > >>     bridges. If the user wants to explicitely use this feature, they > can > >>     disable ACPI PCI Hot-plug with: > >>             --global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off > >>     Change the bit in _OSC method so that the OS selects ACPI PCI > >> Hot-plug > >>     instead of PCIe Native. > >>     [1] https://gitlab.com/qemu-project/qemu/-/issues/641 > >>     [2] https://bugzilla.redhat.com/show_bug.cgi?id=2006409 > >>     Signed-off-by: Julia Suvorova <jus...@redhat.com> > >>     Signed-off-by: Igor Mammedov <imamm...@redhat.com> > >>     Message-Id: <20211112110857.3116853-5-imamm...@redhat.com> > >>     Reviewed-by: Ani Sinha <a...@anisinha.ca> > >>     Reviewed-by: Michael S. Tsirkin <m...@redhat.com> > >>     Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > >> > >> > >> The patch description says it all. Instead of masking out the HPC bit > in > >> pcie slots, we keep them turned on. Instead, we do not advertize native > >> hotplug capability for PCIE using _OSC control method. See section > >> 6.2.11 in ACPI spec 6.2. At the same time, we turn on ACPI hotplug for > >> these slots so now the guest OS can select ACPI hotplug instead. > >> > >> The second change is introduction of a property with which we keep the > >> existing behavior for pc-q35-6.1 machines. This means HPC bit is masked > >> and ACPI hotplug is enabled by default for pcie root ports. > >> The QEMU commit is: > >> > >> (2) commit c318bef76206c2ecb6016e8e68c4ac6ff9a4c8cb > >> Author: Julia Suvorova <jus...@redhat.com> > >> Date:  Fri Nov 12 06:08:54 2021 -0500 > >> > >>     hw/acpi/ich9: Add compat prop to keep HPC bit set for 6.1 machine > >> type > >>     To solve issues [1-2] the Hot Plug Capable bit in PCIe Slots will > be > >>     turned on, while the switch to ACPI Hot-plug will be done in the > >>     DSDT table. > >>     Introducing 'x-keep-native-hpc' property disables the HPC bit only > >>     in 6.1 and as a result keeps the forced 'reserve-io' on > >>     pcie-root-ports in 6.1 too. > >>     [1] https://gitlab.com/qemu-project/qemu/-/issues/641 > >>     [2] https://bugzilla.redhat.com/show_bug.cgi?id=2006409 > >>     Signed-off-by: Julia Suvorova <jus...@redhat.com> > >>     Signed-off-by: Igor Mammedov <imamm...@redhat.com> > >>     Message-Id: <20211112110857.3116853-3-imamm...@redhat.com> > >>     Reviewed-by: Michael S. Tsirkin <m...@redhat.com> > >>     Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > >> > >> Lastly, as a related side note, because from QEMU 6.2 onwards, we do > not > >> mask out HPC bit in PCIE, the work done by this patch is no longer > >> needed: > >> > >> (3) commit e2a6290aab578b2170c1f5909fa556385dc0d820 > >> Author: Marcel Apfelbaum <marcel.apfelb...@gmail.com> > >> Date:  Mon Aug 2 12:00:57 2021 +0300 > >> > >>     hw/pcie-root-port: Fix hotplug for PCI devices requiring IO > >>     Q35 has now ACPI hotplug enabled by default for PCI(e) devices. > >>     As opposed to native PCIe hotplug, guests like Fedora 34 > >>     will not assign IO range to pcie-root-ports not supporting > >>     native hotplug, resulting into a regression. > >>     Reproduce by: > >>         qemu-bin -M q35 -device pcie-root-port,id=p1 -monitor stdio > >>         device_add e1000,bus=p1 > >>     In the Guest OS the respective pcie-root-port will have the IO > range > >>     disabled. > >>     Fix it by setting the "reserve-io" hint capability of the > >>     pcie-root-ports so the firmware will allocate the IO range > instead. > >>     Acked-by: Igor Mammedov <imamm...@redhat.com> > >>     Signed-off-by: Marcel Apfelbaum <mar...@redhat.com> > >>     Message-Id: <20210802090057.1709775-1-mar...@redhat.com> > >>     Reviewed-by: Michael S. Tsirkin <m...@redhat.com> > >>     Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > >> > >> This is what commit (2) alludes to. In pc-q35-6.1 machines we do need > >> patch (3) since we mask out HPC bit from pcie ports. > >> > >> > >> I know this is convoluted mess. In fairness I am trying all I can in my > >> spare time to help from the QEMU side. I am determined to see this > >> patchset through into libvirt. > >> > >> Thanks > >> > >> > >> Ani Sinha (4): > >>   qemu: capablities: detect acpi-pci-hotplug-with-bridge-support > >>   conf: introduce support for acpi-bridge-hotplug feature > >>   qemu: command: add support for acpi-bridge-hotplug feature > >>   NEWS: document new acpi pci hotplug config option > >> > >>  NEWS.rst                                     | 8 ++ > >>  docs/formatdomain.rst                        | 32 +++++++ > >>  docs/schemas/domaincommon.rng                | 15 ++++ > >>  src/conf/domain_conf.c                       | 89 > ++++++++++++++++++- > >>  src/conf/domain_conf.h                       | 9 ++ > >>  src/qemu/qemu_capabilities.c                 | 4 + > >>  src/qemu/qemu_capabilities.h                 | 3 + > >>  src/qemu/qemu_command.c                      | 19 ++++ > >>  src/qemu/qemu_validate.c                     | 42 +++++++++ > >>  .../caps_6.1.0.x86_64.xml                    | 1 + > >>  .../caps_6.2.0.x86_64.xml                    | 1 + > >>  .../caps_7.0.0.x86_64.xml                    | 1 + > >>  ...-hotplug-bridge-disable.aarch64-latest.err | 1 + > >>  .../aarch64-acpi-hotplug-bridge-disable.xml  | 13 +++ > >>  ...-hotplug-bridge-disable.x86_64-latest.args | 35 ++++++++ > >>  .../pc-i440fx-acpi-hotplug-bridge-disable.xml | 36 ++++++++ > >>  .../pc-i440fx-acpi-hotplug-bridge-enable.xml | 36 ++++++++ > >>  ...pi-hotplug-bridge-disable.x86_64-6.0.0.err | 1 + > >>  ...-hotplug-bridge-disable.x86_64-latest.args | 38 ++++++++ > >>  .../q35-acpi-hotplug-bridge-disable.xml      | 53 +++++++++++ > >>  .../q35-acpi-hotplug-bridge-enable.xml       | 53 +++++++++++ > >>  tests/qemuxml2argvtest.c                     | 7 ++ > >>  ...i-hotplug-bridge-disable.x86_64-latest.xml | 1 + > >>  ...pi-hotplug-bridge-enable.x86_64-latest.xml | 1 + > >>  ...i-hotplug-bridge-disable.x86_64-latest.xml | 1 + > >>  ...pi-hotplug-bridge-enable.x86_64-latest.xml | 1 + > >>  tests/qemuxml2xmltest.c                      | 4 + > >>  27 files changed, 504 insertions(+), 1 deletion(-) > >>  create mode 100644 > >> tests/qemuxml2argvdata/ > aarch64-acpi-hotplug-bridge-disable.aarch64-latest.err > >> > >>  create mode 100644 > >> tests/qemuxml2argvdata/aarch64-acpi-hotplug-bridge-disable.xml > >>  create mode 100644 > >> tests/qemuxml2argvdata/ > pc-i440fx-acpi-hotplug-bridge-disable.x86_64-latest.args > >> > >>  create mode 100644 > >> tests/qemuxml2argvdata/pc-i440fx-acpi-hotplug-bridge-disable.xml > >>  create mode 100644 > >> tests/qemuxml2argvdata/pc-i440fx-acpi-hotplug-bridge-enable.xml > >>  create mode 100644 > >> tests/qemuxml2argvdata/q35-acpi-hotplug-bridge-disable.x86_64-6.0.0.err > >>  create mode 100644 > >> tests/qemuxml2argvdata/ > q35-acpi-hotplug-bridge-disable.x86_64-latest.args > >>  create mode 100644 > >> tests/qemuxml2argvdata/q35-acpi-hotplug-bridge-disable.xml > >>  create mode 100644 > >> tests/qemuxml2argvdata/q35-acpi-hotplug-bridge-enable.xml > >>  create mode 120000 > >> tests/qemuxml2xmloutdata/ > pc-i440fx-acpi-hotplug-bridge-disable.x86_64-latest.xml > >> > >>  create mode 120000 > >> tests/qemuxml2xmloutdata/ > pc-i440fx-acpi-hotplug-bridge-enable.x86_64-latest.xml > >> > >>  create mode 120000 > >> tests/qemuxml2xmloutdata/ > q35-acpi-hotplug-bridge-disable.x86_64-latest.xml > >> > >>  create mode 120000 > >> tests/qemuxml2xmloutdata/ > q35-acpi-hotplug-bridge-enable.x86_64-latest.xml > >> > > > >
