Re: [PATCH V2] Add a new PIIX option to control PCI hot unplugging of devices on non-root buses

[Michael S. Tsirkin]

On Tue, Apr 28, 2020 at 09:39:16PM +0530, Ani Sinha wrote:
> 
> Ani
> On Apr 28, 2020, 21:35 +0530, Michael S. Tsirkin <address@hidden>, wrote:
> 
>     On Tue, Apr 28, 2020 at 10:16:52AM +0000, Ani Sinha wrote:
> 
>         A new option "use_acpi_unplug" is introduced for PIIX which will
>         selectively only disable hot unplugging of both hot plugged and
>         cold plugged PCI devices on non-root PCI buses. This will prevent
>         hot unplugging of devices from Windows based guests from system
>         tray but will not prevent devices from being hot plugged into the
>         guest.
> 
>         It has been tested on Windows guests.
> 
>         Signed-off-by: Ani Sinha <address@hidden>
> 
> 
>     It's still a non starter until we find something similar for PCIE and
>     SHPC. Do guests check command status? Can some unplug commands fail? 
> 
> 
> Ok I  give up! I thought we debated this on the other thread.

Sorry to hear that.
I'd rather you didn't, and worked on a solution that works for everyone.
Pushing back on merging code is unfortunately the only mechanism
maintainers have to make sure features are complete and
orthogonal to each other, so I'm not sure I can help otherwise.

> 
> 
> 
> 
>         ---
>         hw/acpi/piix4.c | 3 +++
>         hw/i386/acpi-build.c | 40 ++++++++++++++++++++++++++--------------
>         2 files changed, 29 insertions(+), 14 deletions(-)
> 
>         diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
>         index 964d6f5..59fa707 100644
>         --- a/hw/acpi/piix4.c
>         +++ b/hw/acpi/piix4.c
>         @@ -78,6 +78,7 @@ typedef struct PIIX4PMState {
> 
>         AcpiPciHpState acpi_pci_hotplug;
>         bool use_acpi_pci_hotplug;
>         + bool use_acpi_unplug;
> 
>         uint8_t disable_s3;
>         uint8_t disable_s4;
>         @@ -633,6 +634,8 @@ static Property piix4_pm_properties[] = {
>         DEFINE_PROP_UINT8(ACPI_PM_PROP_S4_VAL, PIIX4PMState, s4_val, 2),
>         DEFINE_PROP_BOOL("acpi-pci-hotplug-with-bridge-support", PIIX4PMState,
>         use_acpi_pci_hotplug, true),
>         + DEFINE_PROP_BOOL("acpi-pci-hotunplug-enable-bridge", PIIX4PMState,
>         + use_acpi_unplug, true),
>         DEFINE_PROP_BOOL("memory-hotplug-support", PIIX4PMState,
>         acpi_memory_hotplug.is_enabled, true),
>         DEFINE_PROP_END_OF_LIST(),
>         diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
>         index 23c77ee..71b3ac3 100644
>         --- a/hw/i386/acpi-build.c
>         +++ b/hw/i386/acpi-build.c
>         @@ -96,6 +96,7 @@ typedef struct AcpiPmInfo {
>         bool s3_disabled;
>         bool s4_disabled;
>         bool pcihp_bridge_en;
>         + bool pcihup_bridge_en;
>         uint8_t s4_val;
>         AcpiFadtData fadt;
>         uint16_t cpu_hp_io_base;
>         @@ -240,6 +241,9 @@ static void acpi_get_pm_info(MachineState 
> *machine,
>         AcpiPmInfo *pm)
>         pm->pcihp_bridge_en =
>         object_property_get_bool(obj, "acpi-pci-hotplug-with-bridge-support",
>         NULL);
>         + pm->pcihup_bridge_en =
>         + object_property_get_bool(obj, "acpi-pci-hotunplug-enable-bridge",
>         + NULL);
>         }
> 
>         static void acpi_get_misc_info(AcpiMiscInfo *info)
>         @@ -451,7 +455,8 @@ static void build_append_pcihp_notify_entry(Aml
>         *method, int slot)
>         }
> 
>         static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus
>         *bus,
>         - bool pcihp_bridge_en)
>         + bool pcihp_bridge_en,
>         + bool pcihup_bridge_en)
>         {
>         Aml *dev, *notify_method = NULL, *method;
>         QObject *bsel;
>         @@ -479,11 +484,14 @@ static void build_append_pci_bus_devices(Aml
>         *parent_scope, PCIBus *bus,
>         dev = aml_device("S%.02X", PCI_DEVFN(slot, 0));
>         aml_append(dev, aml_name_decl("_SUN", aml_int(slot)));
>         aml_append(dev, aml_name_decl("_ADR", aml_int(slot << 16)));
>         - method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
>         - aml_append(method,
>         - aml_call2("PCEJ", aml_name("BSEL"), aml_name("_SUN"))
>         - );
>         - aml_append(dev, method);
>         + if (pcihup_bridge_en || pci_bus_is_root(bus)) {
>         + method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
>         + aml_append(method,
>         + aml_call2("PCEJ", aml_name("BSEL"),
>         + aml_name("_SUN"))
>         + );
>         + aml_append(dev, method);
>         + }
>         aml_append(parent_scope, dev);
> 
>         build_append_pcihp_notify_entry(notify_method, slot);
>         @@ -537,12 +545,14 @@ static void build_append_pci_bus_devices(Aml
>         *parent_scope, PCIBus *bus,
>         /* add _SUN/_EJ0 to make slot hotpluggable */
>         aml_append(dev, aml_name_decl("_SUN", aml_int(slot)));
> 
>         - method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
>         - aml_append(method,
>         - aml_call2("PCEJ", aml_name("BSEL"), aml_name("_SUN"))
>         - );
>         - aml_append(dev, method);
>         -
>         + if (pcihup_bridge_en || pci_bus_is_root(bus)) {
>         + method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
>         + aml_append(method,
>         + aml_call2("PCEJ", aml_name("BSEL"),
>         + aml_name("_SUN"))
>         + );
>         + aml_append(dev, method);
>         + }
>         if (bsel) {
>         build_append_pcihp_notify_entry(notify_method, slot);
>         }
>         @@ -553,7 +563,8 @@ static void build_append_pci_bus_devices(Aml
>         *parent_scope, PCIBus *bus,
>         */
>         PCIBus *sec_bus = pci_bridge_get_sec_bus(PCI_BRIDGE(pdev));
> 
>         - build_append_pci_bus_devices(dev, sec_bus, pcihp_bridge_en);
>         + build_append_pci_bus_devices(dev, sec_bus, pcihp_bridge_en,
>         + pcihup_bridge_en);
>         }
>         /* slot descriptor has been composed, add it into parent context */
>         aml_append(parent_scope, dev);
>         @@ -2196,7 +2207,8 @@ build_dsdt(GArray *table_data, BIOSLinker
>         *linker,
>         if (bus) {
>         Aml *scope = aml_scope("PCI0");
>         /* Scan all PCI buses. Generate tables to support hotplug. */
>         - build_append_pci_bus_devices(scope, bus, pm->pcihp_bridge_en);
>         + build_append_pci_bus_devices(scope, bus, pm->pcihp_bridge_en,
>         + pm->pcihup_bridge_en);
> 
>         if (TPM_IS_TIS_ISA(tpm)) {
>         if (misc->tpm_version == TPM_VERSION_2_0) {
>         --
>         1.9.4
> 
> 
>