On Thu, Jun 17, 2021 at 10:08 PM Julia Suvorova <jus...@redhat.com> wrote:
> Q35 has three different types of PCI devices hot-plug: PCIe Native, > SHPC Native and ACPI hot-plug. This patch changes the default choice > for cold-plugged bridges from PCIe Native to ACPI Hot-plug with > ability to use SHPC and PCIe Native for hot-plugged bridges. > > I personally think the best of all worlds is to have as default: - Native PCIe hotplug for pcie-root-ports - ACPI hotplug for devices behind PCI bridges (pcie-pci bridge or pci-pci bridge). Having ACPI hotplug *as default* for pcie-root-ports seems weird even if it solves existing bugs (we should solve them...). I am not against having a property to force ACPI hotplug even for pcie root-ports, just not being the default. It doesn't have to be part of this series, it can be a patch on top. I would leave APCI hotplug as an option and not as the default, giving us time to test it, come up with a fix for the pcie-hotplug race and a patch for allowing ACPI hotplug only for the bridges. Thanks, Marcel > This is a list of the PCIe Native hot-plug issues that led to this > change: > * no racy behavior during boot (see 110c477c2ed) > * no delay during deleting - after the actual power off software > must wait at least 1 second before indicating about it. This case > is quite important for users, it even has its own bug: > https://bugzilla.redhat.com/show_bug.cgi?id=1594168 > * no timer-based behavior - in addition to the previous example, > the attention button has a 5-second waiting period, during which > the operation can be canceled with a second press. While this > looks fine for manual button control, automation will result in > the need to queue or drop events, and the software receiving > events in all sort of unspecified combinations of attention/power > indicator states, which is racy and uppredictable. > * fixes: > * https://bugzilla.redhat.com/show_bug.cgi?id=1752465 > * https://bugzilla.redhat.com/show_bug.cgi?id=1690256 > > To return to PCIe Native hot-plug: > -global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off > > Signed-off-by: Julia Suvorova <jus...@redhat.com> > Reviewed-by: Igor Mammedov <imamm...@redhat.com> > --- > hw/acpi/ich9.c | 2 +- > hw/i386/pc.c | 1 + > 2 files changed, 2 insertions(+), 1 deletion(-) > > diff --git a/hw/acpi/ich9.c b/hw/acpi/ich9.c > index bcbd567cb0..daa3cd44b1 100644 > --- a/hw/acpi/ich9.c > +++ b/hw/acpi/ich9.c > @@ -424,7 +424,7 @@ void ich9_pm_add_properties(Object *obj, ICH9LPCPMRegs > *pm) > pm->disable_s3 = 0; > pm->disable_s4 = 0; > pm->s4_val = 2; > - pm->use_acpi_hotplug_bridge = false; > + pm->use_acpi_hotplug_bridge = true; > > object_property_add_uint32_ptr(obj, ACPI_PM_PROP_PM_IO_BASE, > &pm->pm_io_base, OBJ_PROP_FLAG_READ); > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index c6d8d0d84d..cc10589552 100644 > --- a/hw/i386/pc.c > +++ b/hw/i386/pc.c > @@ -98,6 +98,7 @@ GlobalProperty pc_compat_6_0[] = { > { "qemu64" "-" TYPE_X86_CPU, "family", "6" }, > { "qemu64" "-" TYPE_X86_CPU, "model", "6" }, > { "qemu64" "-" TYPE_X86_CPU, "stepping", "3" }, > + { "ICH9-LPC", "acpi-pci-hotplug-with-bridge-support", "off" }, > }; > const size_t pc_compat_6_0_len = G_N_ELEMENTS(pc_compat_6_0); > > -- > 2.30.2 > >
