Re: [Qemu-devel] [RFC PATCH 2/2] VFIO: Clear stale MSIx table during EEH reset

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

On Tue, Aug 26, 2014 at 02:25:47PM -0600, Alex Williamson wrote:
>On Wed, 2014-08-20 at 19:52 +1000, Gavin Shan wrote:
>> The PCI device MSIx table is cleaned out in hardware after EEH PE
>> reset. However, we still hold the stale MSIx entries in QEMU, which
>> should be cleared accordingly. Otherwise, we will run into another
>> (recursive) EEH error and the PCI devices contained in the PE have
>> to be offlined exceptionally.
>> 
>> The patch clears stale MSIx table before EEH PE reset so that MSIx
>> table could be restored properly after EEH PE reset.
>> 
>> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
>> ---
>>  hw/misc/vfio.c | 24 ++++++++++++++++++++++++
>>  1 file changed, 24 insertions(+)
>> 
>> diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
>> index 1a3e7eb..3cf7f02 100644
>> --- a/hw/misc/vfio.c
>> +++ b/hw/misc/vfio.c
>> @@ -4424,6 +4424,8 @@ int vfio_container_ioctl(AddressSpace *as, int32_t groupid,
>>  {
>>      VFIOGroup *group;
>>      VFIOContainer *container;
>> +    VFIODevice *vdev;
>> +    struct vfio_eeh_pe_op *arg;
>
>Define these within the scope of the case since they're not used outside
>of it.
>

Yes, I'll fix.

>>      int ret = -1;
>>  
>>      group = vfio_get_group(groupid, as);
>> @@ -4442,7 +4444,29 @@ int vfio_container_ioctl(AddressSpace *as, int32_t groupid,
>>      switch (req) {
>>      case VFIO_CHECK_EXTENSION:
>>      case VFIO_IOMMU_SPAPR_TCE_GET_INFO:
>> +        break;
>>      case VFIO_EEH_PE_OP:
>> +        arg = (struct vfio_eeh_pe_op *)param;
>> +        switch (arg->op) {
>> +        case VFIO_EEH_PE_RESET_HOT:
>> +        case VFIO_EEH_PE_RESET_FUNDAMENTAL:
>> +            /*
>> +             * The MSIx table will be cleaned out by reset. We need
>> +             * disable it so that it can be reenabled properly. Also,
>> +             * the cached MSIx table should be cleared as it's not
>> +             * reflecting the contents in hardware.
>> +             */
>> +            QLIST_FOREACH(vdev, &group->device_list, next) {
>> +                if (msix_enabled(&vdev->pdev)) {
>> +                    vfio_disable_msix(vdev);
>> +                }
>> +
>> +                msix_reset(&vdev->pdev);
>> +            }
>
>We already have vfio_disable_interrupts(), can't we use that (blindly)?
>Do we really need to call msix_reset()?  If so, should
>vfio_disable_msix() call it?
>

Yes, vfio_disable_interrupts() would be better to be used here as it
can covers all types of interrupt (INTx/MSI/MSIx).

vfio_disable_interrupts() needn't clear MSIx vectors. If you prefer
calling msix_reset() in the function, I guess I have to add one more
parameter to vfio_disable_interrupts() to indicate if we need clear
MSI/MSIx vector:

static void vfio_disable_interrupts(VFIODevice *vdev, bool clr_vector)

>> +
>> +            break;
>
>Extraneous break
>

Yep, I'll remove it.

>> +        }
>> +
>>          break;
>>      default:
>>          /* Return an error on unknown requests */
>
>Thanks,
>Alex
>

Thanks,
Gavin