Re: [PATCH] PCI/MSI: Initialize the prepare descriptor by default

[Naman Jain <namjain@linux.microsoft.com>]

On 7/8/2025 9:38 PM, Bjorn Helgaas wrote:
> On Tue, Jul 08, 2025 at 03:45:05PM +0530, Naman Jain wrote:
>> On 7/8/2025 3:32 PM, Shradha Gupta wrote:
>>> On Tue, Jul 08, 2025 at 10:48:48AM +0530, Naman Jain wrote:
>>>> Plug the default MSI-X prepare descriptor for non-implemented ops by
>>>> default to workaround the inability of Hyper-V vPCI module to setup
>>>> the MSI-X descriptors properly; especially for dynamically allocated
>>>> MSI-X.
>>>>
>>>> Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
>>>> ---
>>>>    drivers/pci/msi/irqdomain.c | 2 ++
>>>>    1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
>>>> index 765312c92d9b..655e99b9c8cc 100644
>>>> --- a/drivers/pci/msi/irqdomain.c
>>>> +++ b/drivers/pci/msi/irqdomain.c
>>>> @@ -84,6 +84,8 @@ static void pci_msi_domain_update_dom_ops(struct msi_domain_info *info)
>>>>    	} else {
>>>>    		if (ops->set_desc == NULL)
>>>>    			ops->set_desc = pci_msi_domain_set_desc;
>>>> +		if (ops->prepare_desc == NULL)
>>>> +			ops->prepare_desc = pci_msix_prepare_desc;
>>>>    	}
>>>>    }
>>>>
>>>> base-commit: 26ffb3d6f02cd0935fb9fa3db897767beee1cb2a
>>>> -- 
>>>> 2.34.1
>>>>
>>>
>>> Hey Naman,
>>>
>>> can you please try your tests with this patch:
>>> https://lore.kernel.org/all/1749651015-9668-1-git-send-email-shradhagupta@linux.microsoft.com/
>>> I think this should help your use case
>>
>> Hey,
>> Thanks for sharing this, this works for me.
>>
>> Closing this thread.
> 
> I guess this means we should ignore this patch?  If it turns out that
> we do need this patch, I'd like to add some details in the commit log
> about what this problem looks like to users.
> 
> Bjorn

Yes, my patch is no longer required, since it was doing the same thing
that Shradha's patch (1-2) were doing, but in a different way. Shradha's
patch is better and would suffice for the use case. Please ignore this
patch.

Thanks.
Regards,
Naman