Re: [PATCH 1/2] vfio: Make vfio-pci available on 64-bit host platforms only

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 26/2/25 18:57, BALATON Zoltan wrote:
> On Wed, 26 Feb 2025, Cédric Le Goater wrote:
>> On 2/26/25 15:12, BALATON Zoltan wrote:
>>> On Wed, 26 Feb 2025, Cédric Le Goater wrote:
>>>> VFIO PCI never worked on PPC32 nor ARM, S390x is 64-bit, it might have
>>>> worked on i386 long ago but we have no plans to further support VFIO
>>>> on any 32-bit host platforms. Restrict to 64-bit host platforms.
>>>>
>>>> Cc: Harsh Prateek Bora <harshpb@linux.ibm.com>
>>>> Cc: Tony Krowiak <akrowiak@linux.ibm.com>
>>>> Cc: Eric Farman <farman@linux.ibm.com>
>>>> Cc: Eric Auger <eric.auger@redhat.com>
>>>> Signed-off-by: Cédric Le Goater <clg@redhat.com>
>>>> ---
>>>> hw/vfio/Kconfig | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/hw/vfio/Kconfig b/hw/vfio/Kconfig
>>>> index 
>>>> 7cdba0560aa821c88d3420b36f86020575834202..6ed825429a9151fcdff33e95d1a310210689b258 100644
>>>> --- a/hw/vfio/Kconfig
>>>> +++ b/hw/vfio/Kconfig
>>>> @@ -7,7 +7,7 @@ config VFIO_PCI
>>>>     default y
>>>>     select VFIO
>>>>     select EDID
>>>> -    depends on LINUX && PCI
>>>> +    depends on LINUX && PCI && (AARCH64 || PPC64 || X86_64 || S390X)
>>>
>>> Are these defined for the host or target? 
>>
>> host.
> 
> Where are these defined? I thought compiling qemu-system-ppc on x64_64 
> or aarch64 would have PPC defined not X86_64 or AARCH64 but I could well 
> be missing something.
> 
>>> I see PPC is defined in target/ppc/Kconfig so I think these mark the 
>>> target not the host. Vfio-pci works with qemu-system-ppc 
>>
>> Ah ! I am surprised. Which host and QEMU machine please ?
> 
> I've seen people do this on x86_64 host

Since this patch does:

   LINUX && PCI && (...  X86_64 ...)

these users won't see any change.

> with pegasos2, amigaone and 
> mac99 running 32 bit guests (AmigaOS and MacOS). Some people running 
> older 32 bit Windows versions on pc machine might also use this.
> 
>>> and we are trying to use it for GPU pass through for 32 bit PPC 
>>> guests. Please keep that enabled.
>>
>> As per commit 6d701c9bac1d3571e9ad511e01b27df7237f0b13 "meson: Deprecate
>> 32-bit host support", support will be fully removed in 2 releases and
>> it doesn't need to be addressed by VFIO.
> 
> That's about removing support for compiling QEMU on 32 bit host OSes not 
> using 32 bit guests with qemu-system-ppc and qemu-system-i386 isn't it?
> 
> Regards,
> BALATON Zoltan