On Thu, Feb 24, 2022 at 12:44:07PM -0500, Igor Mammedov wrote: > Currently ACPI PCI hotplug is enabled by default for Q35 machine > type and overrides native PCIe hotplug. It works as expected when > a PCIe device is hotplugged into slot, however the device becomes > in-operational after migration. Which is caused by BARs being > disabled on target due to powered off status of the slot. > > Proposed fix disables power control on PCIe slot when ACPI pcihp > takes over hotplug control and makes PCIe slot check if power > control is enabled before trying to change slot's power. Which > leaves slot always powered on and that makes PCI core keep BARs > enabled.
I thought some more about this. One of the reasons we did not remove the hotplug capability is really so it's easier to layer acpi on top of pcihp if we want to do it down the road. And it would be quite annoying if we had to add more hack to go back to having capability. How about instead of patch 3 we call pci_set_power(dev, true) for all devices where ACPI is managing hotplug immediately on plug? This will fix the bug avoiding headache with migration. Patch 2 does seem like a good idea. > PS: > it's still hacky approach as all ACPI PCI hotplug is, but it's > the least intrusive one. Alternative, I've considered, could be > chaining hotplug callbacks and making pcihp ones call overriden > native callbacks while inhibiting hotplug event in native callbacks > somehow. But that were a bit more intrusive and spills over to SHPC > if implemented systematically, so I ditched that for now. It could > be resurrected later on if current approach turns out to be > insufficient. > > RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=2053584 > CC: m...@redhat.com > CC: kra...@redhat.com > > Igor Mammedov (4): > pci: expose TYPE_XIO3130_DOWNSTREAM name > pcie: update slot power status only is power control is enabled > acpi: pcihp: disable power control on PCIe slot > q35: compat: keep hotplugged PCIe device broken after migration for > 6.2-older machine types > > include/hw/acpi/pcihp.h | 4 +++- > include/hw/pci-bridge/xio3130_downstream.h | 15 +++++++++++++++ > hw/acpi/acpi-pci-hotplug-stub.c | 3 ++- > hw/acpi/ich9.c | 21 ++++++++++++++++++++- > hw/acpi/pcihp.c | 16 +++++++++++++++- > hw/acpi/piix4.c | 3 ++- > hw/core/machine.c | 4 +++- > hw/pci-bridge/xio3130_downstream.c | 3 ++- > hw/pci/pcie.c | 5 ++--- > 9 files changed, 64 insertions(+), 10 deletions(-) > create mode 100644 include/hw/pci-bridge/xio3130_downstream.h > > -- > 2.31.1
