Re: [PATCH v3 17/29] hw/arm/virt-acpi-build: Modify the DSDT ACPI table to enable ACPI PCI hotplug

[Eric Auger <eauger@redhat.com>]

Hi Igor,

On 6/25/25 5:23 PM, Eric Auger wrote:
> Hi Igor, Jonathan,
> 
> On 6/20/25 6:13 PM, Jonathan Cameron wrote:
>> On Fri, 20 Jun 2025 14:38:22 +0200
>> Igor Mammedov <imammedo@redhat.com> wrote:
>>
>>> On Fri, 20 Jun 2025 10:35:38 +0100
>>> Jonathan Cameron <Jonathan.Cameron@huawei.com> wrote:
>>>
>>>> On Mon, 16 Jun 2025 11:46:46 +0200
>>>> Eric Auger <eric.auger@redhat.com> wrote:
>>>>   
>>>>> Modify the DSDT ACPI table to enable ACPI PCI hotplug.
>>>>>
>>>>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>>>>
>>>>> ---
>>>>> v2 -> v3:
>>>>> - use ACPI_PCIHP_SIZE instead of 0x1000 (Igor)
>>>>> - use cihp_state->use_acpi_hotplug_bridge    
>>>> pcihp_state
>>>>
>>>> Takes a bit of searching to find the various bits of the
>>>> same support on x86 but this seems to match up.
>>>> Exactly when things are built does vary but not I think
>>>> in a way that matters.  e.g. I think on x86 the
>>>> EDSM stuff is built whether or not we have pcihp enabled
>>>> whereas here you've made it conditional on using acpi
>>>> hp.  Perhaps a tiny bit more description on that would be
>>>> useful if you do a v4?  
>>> edsm should be built regardless of pcihp
>>> (well intention was there, whether I messed it up or not I don't know)
>>>
>>> idea is that non hotplug ports can have a static acpi-index,
>>> so it doesn't depend on pcihp.
>> That makes sense - so here should that edsm feature be enabled whether
>> or not we have pcihp_state->use_acpi_hotplug_bridge == true
>>
>> i.e. is it really a separate thing from the rest of this series?
> 
> Further studying this comment,
> 
> EDSM is invoked by code generated in aml_pci_static_endpoint_dsm() whcih
> itself is invoked by build_append_pci_bus_devices()
> 
> So to me it means that if we generate edsm unconditionally we also need
> to call the following block unconditionnally
> 
> +    aml_append(pci0_scope, build_pci_bridge_edsm());
> +    build_append_pci_bus_devices(pci0_scope, vms->bus);
> +    if (object_property_find(OBJECT(vms->bus), ACPI_PCIHP_PROP_BSEL)) {
> +        build_append_pcihp_slots(pci0_scope, vms->bus);
> +    }
> 
> which seems to be done that way in hw/i386/acpi-build.c/build_dsdt()
> 
> Igor, if I recall correctly you said that addition changes related to
> "S%.02X" could change the guest ABI. And in that case this wouldn't be
> guarded by any new option/compat. So that's annoying.
> 
> By the way I tested static acpi-index on ARM with resulting code and it
> does not not seem to work - maybe I try with a wrong topology though
> (pcie root port + virtio-net acpi-index)-. I have not checked on x86 yet.
I tested on x86 and if you turn off acpi pci hotplug by setting
-global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off
and you statically instantiate a virtio-net-pci device on a pcie root
port with ,acpi-index=3, acpi-index does not work either.
guest exposes enp5s0.

if you remove the global prop setting (acpi pcihp enabled by default),
guest exposes eno3.

so static acpi-index also seems to be dependent on acpi-pcihp on x86.

So I intend to leave the code as is with edsm added within the
acpi_pcihp conditional block. It is also simpler in terms of ref blob
and most importantly with regards to compat handling.

Thanks

Eric



> 
> So I wonder if it makes sense to do that refinement now. Maybe we can
> check try to improve that afterwards?
> 
> What do you think?
> 
> Eric
> 
> 
> 
>>
>> Thanks,
>>
>> J
>>>> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
>>>>
>>>>   
>>>>> ---
>>>>>  include/hw/acpi/pcihp.h  |  2 ++
>>>>>  include/hw/arm/virt.h    |  1 +
>>>>>  hw/arm/virt-acpi-build.c | 22 ++++++++++++++++++++++
>>>>>  hw/arm/virt.c            |  2 ++
>>>>>  hw/arm/Kconfig           |  2 ++
>>>>>  5 files changed, 29 insertions(+)
>>>>>
>>>>> diff --git a/include/hw/acpi/pcihp.h b/include/hw/acpi/pcihp.h
>>>>> index 5506a58862..9ff548650b 100644
>>>>> --- a/include/hw/acpi/pcihp.h
>>>>> +++ b/include/hw/acpi/pcihp.h
>>>>> @@ -38,6 +38,8 @@
>>>>>  #define ACPI_PCIHP_SEJ_BASE 0x8
>>>>>  #define ACPI_PCIHP_BNMR_BASE 0x10
>>>>>  
>>>>> +#define ACPI_PCIHP_SIZE 0x0018
>>>>> +
>>>>>  typedef struct AcpiPciHpPciStatus {
>>>>>      uint32_t up;
>>>>>      uint32_t down;
>>>>> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
>>>>> index 9a1b0f53d2..0ed2e6b732 100644
>>>>> --- a/include/hw/arm/virt.h
>>>>> +++ b/include/hw/arm/virt.h
>>>>> @@ -79,6 +79,7 @@ enum {
>>>>>      VIRT_ACPI_GED,
>>>>>      VIRT_NVDIMM_ACPI,
>>>>>      VIRT_PVTIME,
>>>>> +    VIRT_ACPI_PCIHP,
>>>>>      VIRT_LOWMEMMAP_LAST,
>>>>>  };
>>>>>  
>>>>> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
>>>>> index d7547c8d3b..a2e58288f8 100644
>>>>> --- a/hw/arm/virt-acpi-build.c
>>>>> +++ b/hw/arm/virt-acpi-build.c
>>>>> @@ -34,6 +34,7 @@
>>>>>  #include "hw/core/cpu.h"
>>>>>  #include "hw/acpi/acpi-defs.h"
>>>>>  #include "hw/acpi/acpi.h"
>>>>> +#include "hw/acpi/pcihp.h"
>>>>>  #include "hw/nvram/fw_cfg_acpi.h"
>>>>>  #include "hw/acpi/bios-linker-loader.h"
>>>>>  #include "hw/acpi/aml-build.h"
>>>>> @@ -809,6 +810,8 @@ static void
>>>>>  build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
>>>>>  {
>>>>>      VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
>>>>> +    AcpiGedState *acpi_ged_state = ACPI_GED(vms->acpi_dev);
>>>>> +    AcpiPciHpState *pcihp_state = &acpi_ged_state->pcihp_state;
>>>>>      Aml *scope, *dsdt;
>>>>>      MachineState *ms = MACHINE(vms);
>>>>>      const MemMapEntry *memmap = vms->memmap;
>>>>> @@ -868,6 +871,25 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
>>>>>  
>>>>>      aml_append(dsdt, scope);
>>>>>  
>>>>> +    if (pcihp_state->use_acpi_hotplug_bridge) {
>>>>> +        Aml *pci0_scope = aml_scope("\\_SB.PCI0");
>>>>> +
>>>>> +        aml_append(pci0_scope, aml_pci_edsm());
>>>>> +        build_acpi_pci_hotplug(dsdt, AML_SYSTEM_MEMORY,
>>>>> +                               memmap[VIRT_ACPI_PCIHP].base);
>>>>> +        build_append_pcihp_resources(pci0_scope,
>>>>> +                                     memmap[VIRT_ACPI_PCIHP].base,
>>>>> +                                     memmap[VIRT_ACPI_PCIHP].size);
>>>>> +
>>>>> +        /* Scan all PCI buses. Generate tables to support hotplug. */
>>>>> +        build_append_pci_bus_devices(pci0_scope, vms->bus);
>>>>> +        if (object_property_find(OBJECT(vms->bus), ACPI_PCIHP_PROP_BSEL)) {
>>>>> +            build_append_pcihp_slots(pci0_scope, vms->bus);
>>>>> +        }
>>>>> +        build_append_notification_callback(pci0_scope, vms->bus);
>>>>> +        aml_append(dsdt, pci0_scope);
>>>>> +    }
>>>>> +
>>>>>      /* copy AML table into ACPI tables blob */
>>>>>      g_array_append_vals(table_data, dsdt->buf->data, dsdt->buf->len);
>>>>>      
>>>>   
>>>
>