Re: [PATCH v2 05/11] xen/arm: Mark device as PCI while creating one

[Jan Beulich <jbeulich@xxxxxxxx>]

On 28.09.2021 10:29, Oleksandr Andrushchenko wrote:
> 
> On 28.09.21 11:26, Jan Beulich wrote:
>> On 28.09.2021 10:09, Oleksandr Andrushchenko wrote:
>>> On 27.09.21 13:26, Jan Beulich wrote:
>>>> On 27.09.2021 12:04, Oleksandr Andrushchenko wrote:
>>>>> On 27.09.21 13:00, Jan Beulich wrote:
>>>>>> On 27.09.2021 11:35, Oleksandr Andrushchenko wrote:
>>>>>>> On 27.09.21 12:19, Jan Beulich wrote:
>>>>>>>> On 27.09.2021 10:45, Oleksandr Andrushchenko wrote:
>>>>>>>>> On 27.09.21 10:45, Jan Beulich wrote:
>>>>>>>>>> On 23.09.2021 14:54, Oleksandr Andrushchenko wrote:
>>>>>>>>>>> --- a/xen/drivers/passthrough/pci.c
>>>>>>>>>>> +++ b/xen/drivers/passthrough/pci.c
>>>>>>>>>>> @@ -328,6 +328,9 @@ static struct pci_dev *alloc_pdev(struct 
>>>>>>>>>>> pci_seg *pseg, u8 bus, u8 devfn)
>>>>>>>>>>>           *((u8*) &pdev->bus) = bus;
>>>>>>>>>>>           *((u8*) &pdev->devfn) = devfn;
>>>>>>>>>>>           pdev->domain = NULL;
>>>>>>>>>>> +#ifdef CONFIG_ARM
>>>>>>>>>>> +    pci_to_dev(pdev)->type = DEV_PCI;
>>>>>>>>>>> +#endif
>>>>>>>>>> I have to admit that I'm not happy about new CONFIG_<arch> 
>>>>>>>>>> conditionals
>>>>>>>>>> here. I'd prefer to see this done by a new arch helper, unless there 
>>>>>>>>>> are
>>>>>>>>>> obstacles I'm overlooking.
>>>>>>>>> Do you mean something like arch_pci_alloc_pdev(dev)?
>>>>>>>> I'd recommend against "alloc" in its name; "new" instead maybe?
>>>>>>> I am fine with arch_pci_new_pdev, but arch prefix points to the fact 
>>>>>>> that
>>>>>>> this is just an architecture specific part of the pdev allocation 
>>>>>>> rather than
>>>>>>> actual pdev allocation itself, so with this respect arch_pci_alloc_pdev 
>>>>>>> seems
>>>>>>> more natural to me.
>>>>>> The bulk of the function is about populating the just allocated struct.
>>>>>> There's no arch-specific part of the allocation (so far, leaving aside
>>>>>> MSI-X), you only want and arch-specific part of the initialization. I
>>>>>> would agree with "alloc" in the name if further allocation was to
>>>>>> happen there.
>>>>> Hm, then arch_pci_init_pdev sounds more reasonable
>>>> Fine with me.
>>> Do we want this to be void or returning an error code? If error code is 
>>> needed,
>>> then we would also need a roll-back function, e.g. arch_pci_free_pdev or
>>> arch_pci_release_pdev or arch_pci_fini_pdev or something, so it can be used 
>>> in
>>> case of error or in free_pdev function.
>> I'd start with void and make it return an error (and deal with necessary
>> cleanup) only once a need arises.
> 
> Sounds reasonable. For x86 I think we can deal with:
> 
> xen/include/xen/pci.h:
> 
> #ifdef CONFIG_ARM
> void arch_pci_init_pdev(struct pci_dev *pdev);
> #else
> static inline void arch_pci_init_pdev(struct pci_dev *pdev)
> {
>      return 0;
> }
> #endif

But that's still #ifdef-ary. We have asm/pci.h.

Jan