Re: [XEN PATCH v8 1/5] xen/vpci: Clear all vpci status of device

["Chen, Jiqian" <Jiqian.Chen@xxxxxxx>]

On 2024/5/17 18:31, Jan Beulich wrote:
> On 17.05.2024 12:00, Chen, Jiqian wrote:
>> On 2024/5/17 17:50, Jan Beulich wrote:
>>> On 17.05.2024 11:28, Chen, Jiqian wrote:
>>>> On 2024/5/17 16:20, Jan Beulich wrote:
>>>>> On 17.05.2024 10:08, Chen, Jiqian wrote:
>>>>>> On 2024/5/16 21:08, Jan Beulich wrote:
>>>>>>> On 16.05.2024 11:52, Jiqian Chen wrote:
>>>>>>>>  struct physdev_pci_device {
>>>>>>>>      /* IN */
>>>>>>>>      uint16_t seg;
>>>>>>>
>>>>>>> Is re-using this struct for this new sub-op sufficient? IOW are all
>>>>>>> possible resets equal, and hence it doesn't need specifying what kind of
>>>>>>> reset was done? For example, other than FLR most reset variants reset 
>>>>>>> all
>>>>>>> functions in one go aiui. Imo that would better require only a single
>>>>>>> hypercall, just to avoid possible confusion. It also reads as if FLR 
>>>>>>> would
>>>>>>> not reset as many registers as other reset variants would.
>>>>>> If I understood correctly that you mean in this hypercall it needs to 
>>>>>> support resetting both one function and all functions of a slot(dev)?
>>>>>> But it can be done for caller to use a cycle to call this reset 
>>>>>> hypercall for each slot function.
>>>>>
>>>>> It could, yes, but since (aiui) there needs to be an indication of the
>>>>> kind of reset anyway, we can as well avoid relying on the caller doing
>>>>> so (and at the same time simplify what the caller needs to do).
>>>> Since the corresponding kernel patch has been merged into linux_next branch
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20240515&id=b272722511d5e8ae580f01830687b8a6b2717f01,
>>>> if it's not very mandatory and necessary, just let the caller handle it 
>>>> temporarily.
>>>
>>> As also mentioned for the other patch having a corresponding kernel one:
>>> The kernel patch would imo better not be merged until the new sub-op is
>>> actually finalized.
>> OK, what should I do next step?
>> Upstream a patch to revert the merged patch on kernel side?
>>
>>>
>>>> Or it can add a new hypercall to reset all functions in one go in future 
>>>> potential requirement, like PHYSDEVOP_pci_device_state_reset_all_func.
>>>
>>> I disagree. We shouldn't introduce incomplete sub-ops. At the very least,
>>> if you want to stick to the present form, I'd expect you to supply reasons
>>> why distinguishing different reset forms is not necessary (now or later).
>> OK, if want to distinguish different reset, is it acceptable to add a 
>> parameter, like "u8 flag", and reset every function if corresponding bit is 
>> 1?
> 
> I'm afraid a boolean won't do, at least not long term. I think it wants to
> be an enumeration (i.e. a set of enumeration-like #define-s). And just to
> stress it again: The extra argument is _not_ primarily for the looping over
> all functions. It is to convey the kind of reset that was done. The single
> vs all function(s) aspect is just a useful side effect this will have.
Do you mean, like:
enum RESET_DEVICE_STATE {
        RESET_DEVICE_SINGLE_FUNC,
        RESET_DEVICE_ALL_FUNC,
        Others
};
If caller pass in RESET_DEVICE_SINGLE_FUNC, I call what I add in this patch, as 
for other types call other functions if added in future?

> 
> Jan

-- 
Best regards,
Jiqian Chen.