Re: [PATCH V6] Introduce a new flag for i440fx to disable PCI hotplug on the root bus

[Ani Sinha]

On Fri, Aug 21, 2020 at 6:07 PM Igor Mammedov <imammedo@redhat.com> wrote:
>
> On Fri, 21 Aug 2020 16:43:37 +0530
> Ani Sinha <ani@anisinha.ca> wrote:
>
> > On Fri, Aug 21, 2020 at 2:46 PM Igor Mammedov <imammedo@redhat.com> wrote:
> > >
> > > On Thu, 20 Aug 2020 22:11:41 +0530
> > > Ani Sinha <ani@anisinha.ca> wrote:
> > >
> > > > > On Aug 20, 2020, at 9:11 PM, Ani Sinha <ani@anisinha.ca> wrote:
> > > > >
> > > > > On Thu, Aug 20, 2020 at 7:37 PM Igor Mammedov <imammedo@redhat.com> 
> > > > > wrote:
> > > > >>
> > > > >>> On Thu, 20 Aug 2020 14:51:56 +0530
> > > > >>> Ani Sinha <ani@anisinha.ca> wrote:
> > > > >>>
> > > > >>> We introduce a new global flag 'acpi-root-pci-hotplug' for i440fx 
> > > > >>> with which
> > > > >>> we can turn on or off PCI device hotplug on the root bus. This flag 
> > > > >>> can be
> > > > >>> used to prevent all PCI devices from getting hotplugged or 
> > > > >>> unplugged from the
> > > > >>> root PCI bus.
> > > > >>> This feature is targetted mostly towards Windows VMs. It is useful 
> > > > >>> in cases
> > > > >>> where some hypervisor admins want to deploy guest VMs in a way so 
> > > > >>> that the
> > > > >>> users of the guest OSes are not able to hot-eject certain PCI 
> > > > >>> devices from
> > > > >>> the Windows system tray. Laine has explained the use case here in 
> > > > >>> detail:
> > > > >>> https://www.redhat.com/archives/libvir-list/2020-February/msg00110.html
> > > > >>>
> > > > >>> Julia has resolved this issue for PCIE buses with the following 
> > > > >>> commit:
> > > > >>> 530a0963184e57e71a5b538 ("pcie_root_port: Add hotplug disabling 
> > > > >>> option")
> > > > >>>
> > > > >>> This commit attempts to introduce similar behavior for PCI root 
> > > > >>> buses used in
> > > > >>> i440fx machine types (although in this case, we do not have a 
> > > > >>> per-slot
> > > > >>> capability to turn hotplug on or off).
> > > > >>>
> > > > >>> Usage:
> > > > >>>   -global PIIX4_PM.acpi-root-pci-hotplug=off
> > > > >>>
> > > > >>> By default, this option is enabled which means that hotplug is 
> > > > >>> turned on for
> > > > >>> the PCI root bus.
> > > > >>>
> > > > >>> The previously existing flag 'acpi-pci-hotplug-with-bridge-support' 
> > > > >>> for PCI-PCI
> > > > >>> bridges remain as is and can be used along with this new flag to 
> > > > >>> control PCI
> > > > >>> hotplug on PCI bridges.
> > > > >>>
> > > > >>> This change has been tested using a Windows 2012R2 server guest 
> > > > >>> image and also
> > > > >>> with a Windows 2019 server guest image on a Ubuntu 18.04 host using 
> > > > >>> the latest
> > > > >>> master qemu from upstream (v5.1.0 tag).
> > > > >>>
> > > > >>> Signed-off-by: Ani Sinha <ani@anisinha.ca>
> > > > >>> ---
> > > > >>> hw/acpi/piix4.c      |  8 ++++++--
> > > > >>> hw/i386/acpi-build.c | 26 +++++++++++++++++++-------
> > > > >>> 2 files changed, 25 insertions(+), 9 deletions(-)
> > > > >>>
> > > > >>> Change Log:
> > > > >>> V5..V6: specified upstream master tag information off which this 
> > > > >>> patch is
> > > > >>> based off of.
> > > > >>>
> > > > >>> diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
> > > > >>> index 26bac4f16c..4f436e5bf3 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_hotplug_bridge;
> > > > >>> +    bool use_acpi_root_pci_hotplug;
> > > > >>>
> > > > >>>     uint8_t disable_s3;
> > > > >>>     uint8_t disable_s4;
> > > > >>
> > > > >>> @@ -595,8 +596,9 @@ static void 
> > > > >>> piix4_acpi_system_hot_add_init(MemoryRegion *parent,
> > > > >>>                           "acpi-gpe0", GPE_LEN);
> > > > >>>     memory_region_add_subregion(parent, GPE_BASE, &s->io_gpe);
> > > > >>>
> > > > >>> -    acpi_pcihp_init(OBJECT(s), &s->acpi_pci_hotplug, bus, parent,
> > > > >>> -                    s->use_acpi_hotplug_bridge);
> > > > >>> +    if (s->use_acpi_hotplug_bridge || s->use_acpi_root_pci_hotplug)
> > > > >>> +        acpi_pcihp_init(OBJECT(s), &s->acpi_pci_hotplug, bus, 
> > > > >>> parent,
> > > > >>> +                        s->use_acpi_hotplug_bridge);
> > > > >> If intent was to disable hardware part of ACPI hotplug,
> > > > >> then this hunk is not enough. I'd say it introduces bug since you 
> > > > >> are leaving
> > > > >> device_add/del route open and "_E01" AML code around trying to 
> > > > >> access no longer
> > > > >> described/present io ports.
> > > > >>
> > > > >> Without this hunk patch is fine, as a means to hide hotplug from 
> > > > >> Windows.
> > > > >>
> > > > >> If you'd like to disable hw part, you will need to consider case 
> > > > >> where hotplug is
> > > > >> disabled completly and block all related AML and block 
> > > > >> device_add|del.
> > > > >> So it would be a bit more than above hunk.
> > > > >
> > > > > Ok maybe I will just remove it.
> > > > >
> > > > >>
> > > > >>
> > > > >>>     s->cpu_hotplug_legacy = true;
> > > > >>>     object_property_add_bool(OBJECT(s), "cpu-hotplug-legacy",
> > > > >>> @@ -635,6 +637,8 @@ 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_hotplug_bridge, true),
> > > > >>> +    DEFINE_PROP_BOOL("acpi-root-pci-hotplug", PIIX4PMState,
> > > > >>> +                     use_acpi_root_pci_hotplug, 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 b7bcbbbb2a..19a1702ad1 100644
> > > > >>> --- a/hw/i386/acpi-build.c
> > > > >>> +++ b/hw/i386/acpi-build.c
> > > > >>> @@ -95,6 +95,7 @@ typedef struct AcpiPmInfo {
> > > > >>>     bool s3_disabled;
> > > > >>>     bool s4_disabled;
> > > > >>>     bool pcihp_bridge_en;
> > > > >>> +    bool pcihp_root_en;
> > > > >>>     uint8_t s4_val;
> > > > >>>     AcpiFadtData fadt;
> > > > >>>     uint16_t cpu_hp_io_base;
> > > > >>> @@ -245,6 +246,9 @@ 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->pcihp_root_en =
> > > > >>> +        object_property_get_bool(obj, "acpi-root-pci-hotplug", 
> > > > >>> NULL);
> > > > >>> +
> > > > >>> }
> > > > >>>
> > > > >>> static void acpi_get_misc_info(AcpiMiscInfo *info)
> > > > >>> @@ -337,15 +341,18 @@ 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 pcihp_root_en)
> > > > >>> {
> > > > >>>     Aml *dev, *notify_method = NULL, *method;
> > > > >>>     QObject *bsel;
> > > > >>>     PCIBus *sec;
> > > > >>>     int i;
> > > > >>> +    bool root_bus = pci_bus_is_root(bus);
> > > > >>> +    bool root_pcihp_disabled = (root_bus && !pcihp_root_en);
> > > > >>>
> > > > >>>     bsel = object_property_get_qobject(OBJECT(bus), 
> > > > >>> ACPI_PCIHP_PROP_BSEL, NULL);
> > > > >>> -    if (bsel) {
> > > > >>> +    if (bsel && !root_pcihp_disabled) {
> > > > >>
> > > > >> have you considered to make bus not hotpluggable,
> > > > >> which should make it not to have bsel, and hence skip this branch 
> > > > >> without
> > > > >> root_pcihp_disabled?
> > > > >>
> > > > >> see: acpi_set_bsel()
> > > > >>
> > > > >>
> > > > >> maybe you can drop pcihp_root_en and use bsel instead of it then.
> > > > >>
> > > > >> it also should block device_add/del route.
> > > > >
> > > > > This is a good idea. Therefore, I tried this:
> > > > >
> > > > > --- a/hw/acpi/piix4.c
> > > > > +++ b/hw/acpi/piix4.c
> > > > > @@ -28,6 +28,7 @@
> > > > > #include "hw/pci/pci.h"
> > > > > #include "hw/qdev-properties.h"
> > > > > #include "hw/acpi/acpi.h"
> > > > > +#include "hw/pci/pci_bus.h"
> > > > > #include "sysemu/runstate.h"
> > > > > #include "sysemu/sysemu.h"
> > > > > #include "sysemu/xen.h"
> > > > > @@ -507,7 +508,9 @@ static void piix4_pm_realize(PCIDevice *dev, 
> > > > > Error **errp)
> > > > >
> > > > >     piix4_acpi_system_hot_add_init(pci_address_space_io(dev),
> > > > >                                    pci_get_bus(dev), s);
> > > > > -    qbus_set_hotplug_handler(BUS(pci_get_bus(dev)), OBJECT(s));
> > > > > +    if (s->use_acpi_root_pci_hotplug ||
> > > > > +        !pci_bus_is_root(pci_get_bus(dev)))
> > > > > +        qbus_set_hotplug_handler(BUS(pci_get_bus(dev)), OBJECT(s));
> > > > >
> > > > >     piix4_pm_add_propeties(s);
> > > > > }
> > > > >
> > > > >
> > > > > but this does not seem to be working. I am out of ideas as to why it
> > > > > wouldn't work :(
> > > >
> > > > By that I mean the devices attached to bridges also seems to be 
> > > > disabled from hotplug from within Windows. I do not understand why that 
> > > > would be the case when the pci_bus_is_root() should be false for the 
> > > > secondary buses.
> > > >
> > > >  Any ideas?
> > > Looking at acpi_set_pci_info() and debugging it might help.
> >
> > All my efforts in this space have failed to work :( I am feeling a
> > little frustrated and out of ideas. I am inclined to resend V2 with
> > the suggestions you suggested for the final patch unless you have
> > better ideas.
>
> That's why I've suggest to fix up this patch first, and work on hw part 
> separately.
>
> As for ideas, unfortunatly other than debugging it to see where it breaks,
> I don't have any other suggestions.
> (though that would require a bit more code studying about how ACPI PCI
> hotplug works. If You have concrete questions about the code,
> I might be able to clarify it for you.)

Ok I have sent a patch V7. I tested against the same two windows
versions and it seems to work. Hope you are OK with the patch.

>
>
> > >
> > > >
> > > > >
> > > > >>
> > > > >>
> > > > >>>         uint64_t bsel_val = qnum_get_uint(qobject_to(QNum, bsel));
> > > > >>>
> > > > >>>         aml_append(parent_scope, aml_name_decl("BSEL", 
> > > > >>> aml_int(bsel_val)));
> > > > >>> @@ -361,6 +368,9 @@ static void build_append_pci_bus_devices(Aml 
> > > > >>> *parent_scope, PCIBus *bus,
> > > > >>>         bool bridge_in_acpi;
> > > > >>>
> > > > >>>         if (!pdev) {
> > > > >>> +            /* skip if pci hotplug for the root bus is disabled */
> > > > >>> +            if (root_pcihp_disabled)
> > > > >>> +                continue;
> > > > >>>             if (bsel) { /* add hotplug slots for non present 
> > > > >>> devices */
> > > > >>>                 dev = aml_device("S%.02X", PCI_DEVFN(slot, 0));
> > > > >>>                 aml_append(dev, aml_name_decl("_SUN", 
> > > > >>> aml_int(slot)));
> > > > >>> @@ -419,7 +429,7 @@ static void build_append_pci_bus_devices(Aml 
> > > > >>> *parent_scope, PCIBus *bus,
> > > > >>>             method = aml_method("_S3D", 0, AML_NOTSERIALIZED);
> > > > >>>             aml_append(method, aml_return(aml_int(s3d)));
> > > > >>>             aml_append(dev, method);
> > > > >>> -        } else if (hotplug_enabled_dev) {
> > > > >>> +        } else if (hotplug_enabled_dev && !root_pcihp_disabled) {
> > > > >>>             /* add _SUN/_EJ0 to make slot hotpluggable  */
> > > > >>>             aml_append(dev, aml_name_decl("_SUN", aml_int(slot)));
> > > > >>>
> > > > >>> @@ -439,13 +449,14 @@ 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,
> > > > >>> +                                         pcihp_root_en);
> > > > >>>         }
> > > > >>>         /* slot descriptor has been composed, add it into parent 
> > > > >>> context */
> > > > >>>         aml_append(parent_scope, dev);
> > > > >>>     }
> > > > >>>
> > > > >>> -    if (bsel) {
> > > > >>> +    if (bsel && !root_pcihp_disabled) {
> > > > >>>         aml_append(parent_scope, notify_method);
> > > > >>>     }
> > > > >>>
> > > > >>> @@ -455,7 +466,7 @@ static void build_append_pci_bus_devices(Aml 
> > > > >>> *parent_scope, PCIBus *bus,
> > > > >>>     method = aml_method("PCNT", 0, AML_NOTSERIALIZED);
> > > > >>>
> > > > >>>     /* If bus supports hotplug select it and notify about local 
> > > > >>> events */
> > > > >>> -    if (bsel) {
> > > > >>> +    if (bsel && !root_pcihp_disabled) {
> > > > >>>         uint64_t bsel_val = qnum_get_uint(qobject_to(QNum, bsel));
> > > > >>>
> > > > >>>         aml_append(method, aml_store(aml_int(bsel_val), 
> > > > >>> aml_name("BNUM")));
> > > > >>> @@ -1818,7 +1829,8 @@ 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->pcihp_root_en);
> > > > >>>
> > > > >>>             if (TPM_IS_TIS_ISA(tpm)) {
> > > > >>>                 if (misc->tpm_version == TPM_VERSION_2_0) {
> > > > >>
> > > >
> > >
> >
>