Re: [PATCH v10 4/4] vpci/msix: Free MSIX resources when init_msix() fails

[Jan Beulich <jbeulich@xxxxxxxx>]

On 06.08.2025 05:35, Chen, Jiqian wrote:
> On 2025/8/5 16:43, Jan Beulich wrote:
>> On 05.08.2025 05:49, Jiqian Chen wrote:
>>> --- a/xen/drivers/vpci/msix.c
>>> +++ b/xen/drivers/vpci/msix.c
>>> @@ -655,6 +655,48 @@ int vpci_make_msix_hole(const struct pci_dev *pdev)
>>>      return 0;
>>>  }
>>>  
>>> +static int cf_check cleanup_msix(const struct pci_dev *pdev)
>>> +{
>>> +    int rc;
>>> +    struct vpci *vpci = pdev->vpci;
>>> +    const unsigned int msix_pos = pdev->msix_pos;
>>> +
>>> +    if ( !msix_pos )
>>> +        return 0;
>>> +
>>> +    rc = vpci_remove_registers(vpci, msix_control_reg(msix_pos), 2);
>>> +    if ( rc )
>>> +    {
>>> +        printk(XENLOG_ERR "%pd %pp: fail to remove MSIX handlers rc=%d\n",
>>> +               pdev->domain, &pdev->sbdf, rc);
>>> +        ASSERT_UNREACHABLE();
>>> +        return rc;
>>> +    }
>>> +
>>> +    if ( vpci->msix )
>>> +    {
>>> +        list_del(&vpci->msix->next);
>>> +        for ( unsigned int i = 0; i < ARRAY_SIZE(vpci->msix->table); i++ )
>>> +            if ( vpci->msix->table[i] )
>>> +                iounmap(vpci->msix->table[i]);
>>> +
>>> +        XFREE(vpci->msix);
>>> +    }
>>> +
>>> +    /*
>>> +     * The driver may not traverse the capability list and think device
>>> +     * supports MSIX by default. So here let the control register of MSIX
>>> +     * be Read-Only is to ensure MSIX disabled.
>>> +     */
>>> +    rc = vpci_add_register(vpci, vpci_hw_read16, NULL,
>>> +                           msix_control_reg(msix_pos), 2, NULL);
>>> +    if ( rc )
>>> +        printk(XENLOG_ERR "%pd %pp: fail to add MSIX ctrl handler rc=%d\n",
>>> +               pdev->domain, &pdev->sbdf, rc);
>>
>> Here as well as for MSI: Wouldn't this better be limited to the init-failure
>> case? No point in adding a register hook (and possibly emitting a misleading
>> log message) when we're tearing down anyway. IOW I think the ->cleanup()
>> hook needs a boolean parameter, unless the distinction of the two cases can
>> be (reliably) inferred from some other property.
> To make these changes, can I add a new patch as the last patch of this series?
> And the new patch will do:
> 1. add a boolean parameter for cleanup hook to separate whose calls 
> cleanup(during initialization or during deassign device).
> 2. call all cleanup hooks in vpci_deassign_device().
> 3. remove the MSI/MSIX specific free actions in vpci_deassign_device().

The outline looks okay, but imo it shouldn't be last in the series. Instead I
think it wants to come ahead of the last three patches; whether it's patch 1
or patch 2 doesn't really matter. Then (3) would be taken care of incrementally,
as ->cleanup hooks are added.

Jan