Re: [RFC PATCH v3 3/7] hw/pci/pcie: Do not initialize slot capability if acpihp is used

[Ani Sinha <ani@anisinha.ca>]

On Thu, 24 Sep 2020, Julia Suvorova wrote:

> On Thu, Sep 24, 2020 at 9:36 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>>
>> On Thu, Sep 24, 2020 at 09:00:09AM +0200, Julia Suvorova wrote:
>>> Instead of changing the hot-plug type in _OSC register, do not
>>> initialize the slot capability or set the 'Slot Implemented' flag.
>>> This way guest will choose ACPI hot-plug if it is preferred and leave
>>> the option to use SHPC with pcie-pci-bridge.
>>>
>>> Signed-off-by: Julia Suvorova <jusual@redhat.com>
>>> ---
>>>  hw/i386/acpi-build.h |  2 ++
>>>  hw/i386/acpi-build.c |  2 +-
>>>  hw/pci/pcie.c        | 16 ++++++++++++++++
>>>  3 files changed, 19 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/i386/acpi-build.h b/hw/i386/acpi-build.h
>>> index 487ec7710f..4c5bfb3d0b 100644
>>> --- a/hw/i386/acpi-build.h
>>> +++ b/hw/i386/acpi-build.h
>>> @@ -11,4 +11,6 @@ extern const struct AcpiGenericAddress x86_nvdimm_acpi_dsmio;
>>>
>>>  void acpi_setup(void);
>>>
>>> +Object *object_resolve_type_unambiguous(const char *typename);
>>> +
>>>  #endif
>>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
>>> index cf503b16af..b7811a8912 100644
>>> --- a/hw/i386/acpi-build.c
>>> +++ b/hw/i386/acpi-build.c
>>> @@ -174,7 +174,7 @@ static void init_common_fadt_data(MachineState *ms, Object *o,
>>>      *data = fadt;
>>>  }
>>>
>>> -static Object *object_resolve_type_unambiguous(const char *typename)
>>> +Object *object_resolve_type_unambiguous(const char *typename)
>>>  {
>>>      bool ambig;
>>>      Object *o = object_resolve_path_type("", typename, &ambig);
>>> diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
>>> index 5b48bae0f6..c1a082e8b9 100644
>>> --- a/hw/pci/pcie.c
>>> +++ b/hw/pci/pcie.c
>>> @@ -27,6 +27,8 @@
>>>  #include "hw/pci/pci_bus.h"
>>>  #include "hw/pci/pcie_regs.h"
>>>  #include "hw/pci/pcie_port.h"
>>> +#include "hw/i386/ich9.h"
>>> +#include "hw/i386/acpi-build.h"
>>>  #include "qemu/range.h"
>>>
>>>  //#define DEBUG_PCIE
>>
>>
>> Not really happy with pcie.c getting an i386 dependency.
>>
>>
>>
>>> @@ -515,12 +517,26 @@ void pcie_cap_slot_unplug_request_cb(HotplugHandler *hotplug_dev,
>>>      pcie_cap_slot_push_attention_button(hotplug_pdev);
>>>  }
>>>
>>> +static bool acpi_pcihp_enabled(void)
>>> +{
>>> +    Object *lpc = object_resolve_type_unambiguous(TYPE_ICH9_LPC_DEVICE);
>>> +
>>> +    return lpc &&
>>> +           object_property_get_bool(lpc, "acpi-pci-hotplug-with-bridge-support",
>>> +                                    NULL);
>>> +
>>> +}
>>> +
>>
>> Why not just check the property unconditionally?
>
> Ok.

I do not see how that would work if lpc is NULL.
object_resolve_type_unambiguous() can return NULL, at least in theory.

>
>>>  /* pci express slot for pci express root/downstream port
>>>     PCI express capability slot registers */
>>>  void pcie_cap_slot_init(PCIDevice *dev, PCIESlot *s)
>>>  {
>>>      uint32_t pos = dev->exp.exp_cap;
>>>
>>> +    if (acpi_pcihp_enabled()) {
>>> +        return;
>>> +    }
>>> +
>>
>> I think I would rather not teach pcie about acpi. How about we
>> change the polarity, name the property
>> "pci-native-hotplug" or whatever makes sense.
>
> I'd prefer not to change the property name since the common code in
> hw/i386/acpi-build.c depends on it, but I can add a new one if it
> makes any sense.
>
>>>      pci_word_test_and_set_mask(dev->config + pos + PCI_EXP_FLAGS,
>>>                                 PCI_EXP_FLAGS_SLOT);
>>>
>>> --
>>> 2.25.4
>>
>
>