On Thu, 13 May 2021 08:26:41 +0200
Julia Suvorova <jusual@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.
>
> 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 or reduces the likelihood of the bug:
> * https://bugzilla.redhat.com/show_bug.cgi?id=1833187
> * https://bugzilla.redhat.com/show_bug.cgi?id=1657077
> * https://bugzilla.redhat.com/show_bug.cgi?id=1669931
> * https://bugzilla.redhat.com/show_bug.cgi?id=1678290
>
> To return to PCIe Native hot-plug:
> -global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off
>
> Signed-off-by: Julia Suvorova <jusual@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
> ---
> hw/acpi/ich9.c | 2 +-
> hw/i386/pc.c | 4 +++-
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/hw/acpi/ich9.c b/hw/acpi/ich9.c
> index f6819c4f2a..e7b2cd9719 100644
> --- a/hw/acpi/ich9.c
> +++ b/hw/acpi/ich9.c
> @@ -425,7 +425,7 @@ 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 8cfaf216e7..5c2d3d11a2 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -94,7 +94,9 @@
> #include "trace.h"
> #include CONFIG_DEVICES
>
> -GlobalProperty pc_compat_6_0[] = {};
> +GlobalProperty pc_compat_6_0[] = {
> + { "ICH9-LPC", "acpi-pci-hotplug-with-bridge-support", "off" },
> +};
> const size_t pc_compat_6_0_len = G_N_ELEMENTS(pc_compat_6_0);
>
> GlobalProperty pc_compat_5_2[] = {