Re: [PATCH 1/5] vfio: use helper to simplfy the failure path in vfio_msi_enable

[Longpeng (Mike, Cloud Infrastructure Service Product Dept.)]

在 2021/9/4 5:55, Alex Williamson 写道:
> On Wed, 25 Aug 2021 15:56:16 +0800
> "Longpeng(Mike)" <longpeng2@huawei.com> wrote:
> 
>> The main difference of the failure path in vfio_msi_enable and
>> vfio_msi_disable_common is enable INTX or not.
>>
>> Extend the vfio_msi_disable_common to provide a arg to decide
> 
> "an arg"
> 

Thanks a lot, I'll fix all of the grammatical errors and typos in this version
together.

>> whether need to fallback, and then we can use this helper to
>> instead the redundant code in vfio_msi_enable.
> 
> Do you mean s/instead/replace/?
> 
>>
>> Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
>> ---
>>  hw/vfio/pci.c | 34 ++++++++++++----------------------
>>  1 file changed, 12 insertions(+), 22 deletions(-)
>>
>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
>> index e1ea1d8..7cc43fe 100644
>> --- a/hw/vfio/pci.c
>> +++ b/hw/vfio/pci.c
>> @@ -47,6 +47,7 @@
>>  
>>  static void vfio_disable_interrupts(VFIOPCIDevice *vdev);
>>  static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool enabled);
>> +static void vfio_msi_disable_common(VFIOPCIDevice *vdev, bool enable_intx);
>>  
>>  /*
>>   * Disabling BAR mmaping can be slow, but toggling it around INTx can
>> @@ -650,29 +651,17 @@ retry:
>>      if (ret) {
>>          if (ret < 0) {
>>              error_report("vfio: Error: Failed to setup MSI fds: %m");
>> -        } else if (ret != vdev->nr_vectors) {
> 
> This part of the change is subtle and not mentioned in the commit log.
> It does seem unnecessary to test against this specific return value
> since any positive return is an error indicating the number of vectors
> we should retry with, but this change should be described in a separate
> patch.
> 
Ok, thanks, I'll split in the next version.

>> +        } else {
>>              error_report("vfio: Error: Failed to enable %d "
>>                           "MSI vectors, retry with %d", vdev->nr_vectors, 
>> ret);
>>          }
>>  
>> -        for (i = 0; i < vdev->nr_vectors; i++) {
>> -            VFIOMSIVector *vector = &vdev->msi_vectors[i];
>> -            if (vector->virq >= 0) {
>> -                vfio_remove_kvm_msi_virq(vector);
>> -            }
>> -            qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
>> -                                NULL, NULL, NULL);
>> -            event_notifier_cleanup(&vector->interrupt);
>> -        }
>> -
>> -        g_free(vdev->msi_vectors);
>> -        vdev->msi_vectors = NULL;
>> +        vfio_msi_disable_common(vdev, false);
>>  
>> -        if (ret > 0 && ret != vdev->nr_vectors) {
>> +        if (ret > 0) {
>>              vdev->nr_vectors = ret;
>>              goto retry;
>>          }
>> -        vdev->nr_vectors = 0;
>>  
>>          /*
>>           * Failing to setup MSI doesn't really fall within any 
>> specification.
>> @@ -680,7 +669,6 @@ retry:
>>           * out to fall back to INTx for this device.
>>           */
>>          error_report("vfio: Error: Failed to enable MSI");
>> -        vdev->interrupt = VFIO_INT_NONE;
>>  
>>          return;
>>      }
>> @@ -688,7 +676,7 @@ retry:
>>      trace_vfio_msi_enable(vdev->vbasedev.name, vdev->nr_vectors);
>>  }
>>  
>> -static void vfio_msi_disable_common(VFIOPCIDevice *vdev)
>> +static void vfio_msi_disable_common(VFIOPCIDevice *vdev, bool enable_intx)
> 
> I'd rather avoid these sort of modal options to functions where we can.
> Maybe this suggests instead that re-enabling INTx should be removed
> from the common helper and callers needing to do so should do it
> outside of the common helper.  Thanks,
> 
Ok, thanks.

> Alex
> 
> 
>>  {
>>      Error *err = NULL;
>>      int i;
>> @@ -710,9 +698,11 @@ static void vfio_msi_disable_common(VFIOPCIDevice *vdev)
>>      vdev->nr_vectors = 0;
>>      vdev->interrupt = VFIO_INT_NONE;
>>  
>> -    vfio_intx_enable(vdev, &err);
>> -    if (err) {
>> -        error_reportf_err(err, VFIO_MSG_PREFIX, vdev->vbasedev.name);
>> +    if (enable_intx) {
>> +        vfio_intx_enable(vdev, &err);
>> +        if (err) {
>> +            error_reportf_err(err, VFIO_MSG_PREFIX, vdev->vbasedev.name);
>> +        }
>>      }
>>  }
>>  
>> @@ -737,7 +727,7 @@ static void vfio_msix_disable(VFIOPCIDevice *vdev)
>>          vfio_disable_irqindex(&vdev->vbasedev, VFIO_PCI_MSIX_IRQ_INDEX);
>>      }
>>  
>> -    vfio_msi_disable_common(vdev);
>> +    vfio_msi_disable_common(vdev, true);
>>  
>>      memset(vdev->msix->pending, 0,
>>             BITS_TO_LONGS(vdev->msix->entries) * sizeof(unsigned long));
>> @@ -748,7 +738,7 @@ static void vfio_msix_disable(VFIOPCIDevice *vdev)
>>  static void vfio_msi_disable(VFIOPCIDevice *vdev)
>>  {
>>      vfio_disable_irqindex(&vdev->vbasedev, VFIO_PCI_MSI_IRQ_INDEX);
>> -    vfio_msi_disable_common(vdev);
>> +    vfio_msi_disable_common(vdev, true);
>>  
>>      trace_vfio_msi_disable(vdev->vbasedev.name);
>>  }
> 
> .
>