Am 09.10.24 um 03:53 schrieb Yuichiro NAITO:
> From: Stefan Fritsch <sf@openbsd.org>
> Subject: Re: PCI amd64: Enables MSI/MSI-X interrupts on QEMU i440fx chipset emulation
> Date: Mon, 7 Oct 2024 22:58:35 +0200 (CEST)
> 
>> On Mon, 7 Oct 2024, Jonathan Gray wrote:
>>
>>> On Mon, Oct 07, 2024 at 05:04:26PM +0900, YASUOKA Masahiko wrote:
>>>> On Mon, 07 Oct 2024 09:06:37 +0200
>>>> Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
>>>>>> Date: Mon, 07 Oct 2024 10:54:14 +0900 (JST)
>>>>>> From: Yuichiro NAITO <naito.yuichiro@gmail.com>
>>>>>>
>>>>>> Hi, this patch sets 'PCI_FLAGS_MSI_ENABLED' if the kernel runs on a QEMU
>>>>>> virtual machine with i440fx chipset emulation. The i440fx is the default
>>>>>> chipset on the QEMU so users will use it first.
>>>>>> And then ixv(4) and iavf(4) will fail because MSI-X interrupts are not
>>>>>> supported by the kernel.
>>>>>>
>>>>>> The i440fx is quite old and the ACPI table is revision 1. We cannot know
>>>>>> if it has MSI capability from the ACPI table. So I add the flag as a quirk.
>>>>>>
>>>>>> The same quirk is implemented in NetBSD.
>>>>>>
>>>>>> https://github.com/NetBSD/src/blob/affb7619d18b17a184eede63a4823f629a2893fc/sys/arch/x86/pci/pci_machdep.c#L273
>>>>>>
>>>>>> FreeBSD seems to have the quirk but is used as the exception for blacklist
>>>>>> devices. Probably they see the PCI device capability header of MSI/MSI-X.
>>>>>> Until we see the same capability, my patch will be useful for the VF driver
>>>>>> users.
>>>>>>
>>>>>> OK?
>>>>>
>>>>> I think this should be done using the subsystem vendir/id stuff like
>>>>> was suggested by someone else in the thread.
>>>>
>>
>>
>>> sf proposed checking the subsystem vendor id
>>> https://marc.info/?l=openbsd-tech&m=172812592731721&w=2
>>> your diff checks the wrong register, should be PCI_SUBSYS_ID_REG
>>
>> I am ok with your diff. But freebsd and netbsd have two intel device ids
>> with that quirk. The other is for vmware, which likely does not have the
>> qumranet subsystem vendor id. I would also be ok with a diff that does it
>> in the same way as the other bsds.
>>
>> I have checked that with your diff, I could remove the quirk in virtio_pci
>> on qemu and msix still works. However, we disable MSI if the host bridge
>> is not Intel/AMD/Nvidia. There are many other hypervisors than qemu and I
>> think this could be a problem if we removed the virtio_pci quirk. Maybe we
>> should simply trust the acpi tables on hypervisors, see diff below (in
>> addition to your diff)? Or trust them on all acpi >= 2 systems?
> 
> I'm afraid that the vmd doesn't offer an ACPI table to a guest OS so that
> a guest OpenBSD kernel doesn't detect msix capability if we remove
> the quirk in the virtio_pci. I think the quirk should be kept until
> the vmd supports ACPI.

Good point. On the other hand, vmd does not support msix yet, so at the 
moment it would not be a problem. But it does not hurt to keep the 
virtio_pci quirk for now.


> 
>> Cheers,
>> Stefan
>>
>> diff --git a/sys/arch/amd64/pci/acpipci.c b/sys/arch/amd64/pci/acpipci.c
>> index ecfb0921d46..d845b0e15bc 100644
>> --- a/sys/arch/amd64/pci/acpipci.c
>> +++ b/sys/arch/amd64/pci/acpipci.c
>> @@ -202,16 +202,18 @@ acpipci_attach_bus(struct device *parent, struct acpipci_softc *sc)
>>   		pba.pba_flags |= PCI_FLAGS_MSI_ENABLED;
>>   
>>   	/*
>>   	 * Don't enable MSI on chipsets from low-end manufacturers
>>   	 * like VIA and SiS.  We do this by looking at the host
>>   	 * bridge, which should be device 0 function 0.
>> +	 * Except on hypervisors, there we trust the acpi info.
>>   	 */
>>   	id = pci_conf_read(pba.pba_pc, tag, PCI_ID_REG);
>>   	class = pci_conf_read(pba.pba_pc, tag, PCI_CLASS_REG);
>> -	if (PCI_CLASS(class) == PCI_CLASS_BRIDGE &&
>> +	if ((cpu_ecxfeature & CPUIDECX_HV) == 0 &&
>> +	    PCI_CLASS(class) == PCI_CLASS_BRIDGE &&
>>   	    PCI_SUBCLASS(class) != PCI_SUBCLASS_BRIDGE_HOST &&
>>   	    PCI_VENDOR(id) != PCI_VENDOR_AMD &&
>>   	    PCI_VENDOR(id) != PCI_VENDOR_NVIDIA &&
>>   	    PCI_VENDOR(id) != PCI_VENDOR_INTEL)
>>   		pba.pba_flags &= ~PCI_FLAGS_MSI_ENABLED;
>>   
>>
>>
>>>
>>> Index: sys/arch/amd64/pci/acpipci.c
>>> ===================================================================
>>> RCS file: /cvs/src/sys/arch/amd64/pci/acpipci.c,v
>>> diff -u -p -r1.8 acpipci.c
>>> --- sys/arch/amd64/pci/acpipci.c	13 May 2024 01:15:50 -0000	1.8
>>> +++ sys/arch/amd64/pci/acpipci.c	7 Oct 2024 09:27:42 -0000
>>> @@ -194,12 +194,18 @@ acpipci_attach_bus(struct device *parent
>>>   	    (sc->sc_acpi->sc_fadt->iapc_boot_arch & FADT_NO_MSI) == 0)
>>>   		pba.pba_flags |= PCI_FLAGS_MSI_ENABLED;
>>>   
>>> +	/* Enable MSI for QEMU claiming ACPI 1.0 */
>>> +	tag = pci_make_tag(pba.pba_pc, sc->sc_bus, 0, 0);
>>> +	id = pci_conf_read(pba.pba_pc, tag, PCI_SUBSYS_ID_REG);
>>> +	if (sc->sc_acpi->sc_fadt->hdr.revision == 1 &&
>>> +	    PCI_VENDOR(id) == PCI_VENDOR_QUMRANET)
>>> +		pba.pba_flags |= PCI_FLAGS_MSI_ENABLED;
>>> +
>>>   	/*
>>>   	 * Don't enable MSI on chipsets from low-end manufacturers
>>>   	 * like VIA and SiS.  We do this by looking at the host
>>>   	 * bridge, which should be device 0 function 0.
>>>   	 */
>>> -	tag = pci_make_tag(pba.pba_pc, sc->sc_bus, 0, 0);
>>>   	id = pci_conf_read(pba.pba_pc, tag, PCI_ID_REG);
>>>   	class = pci_conf_read(pba.pba_pc, tag, PCI_CLASS_REG);
>>>   	if (PCI_CLASS(class) == PCI_CLASS_BRIDGE &&
>>> Index: sys/arch/i386/pci/pci_machdep.c
>>> ===================================================================
>>> RCS file: /cvs/src/sys/arch/i386/pci/pci_machdep.c,v
>>> diff -u -p -r1.87 pci_machdep.c
>>> --- sys/arch/i386/pci/pci_machdep.c	11 Mar 2021 11:16:57 -0000	1.87
>>> +++ sys/arch/i386/pci/pci_machdep.c	7 Oct 2024 09:26:40 -0000
>>> @@ -324,6 +324,11 @@ pci_attach_hook(struct device *parent, s
>>>   		break;
>>>   	}
>>>   
>>> +	/* Enable MSI for QEMU */
>>> +	id = pci_conf_read(pc, tag, PCI_SUBSYS_ID_REG);
>>> +	if (PCI_VENDOR(id) == PCI_VENDOR_QUMRANET)
>>> +		pba->pba_flags |= PCI_FLAGS_MSI_ENABLED;
>>> +
>>>   	/*
>>>   	 * Don't enable MSI on a HyperTransport bus.  In order to
>>>   	 * determine that bus 0 is a HyperTransport bus, we look at
>>>
>>
>