Re: [Qemu-devel] [PATCH v3 8/8] vmxnet3: remove unnecessary internal msix state flag

[Dmitry Fleytman <dmitry@daynix.com>]

> On 30 Sep 2016, at 15:08 PM, Markus Armbruster <armbru@redhat.com> wrote:
> 
> Cao jin <caoj.fnst@cn.fujitsu.com> writes:
> 
>> On 09/29/2016 10:42 PM, Markus Armbruster wrote:
>>> Cao jin <caoj.fnst@cn.fujitsu.com> writes:
>>> 
>> 
>>>>  static int vmxnet3_post_load(void *opaque, int version_id)
>>>>  {
>>>>      VMXNET3State *s = opaque;
>>>> -    PCIDevice *d = PCI_DEVICE(s);
>>>> 
>>>>      net_tx_pkt_init(&s->tx_pkt, PCI_DEVICE(s),
>>>>                      s->max_tx_frags, s->peer_has_vhdr);
>>>>      net_rx_pkt_init(&s->rx_pkt, s->peer_has_vhdr);
>>>> 
>>>> -    if (s->msix_used) {
>>>> -        if  (!vmxnet3_use_msix_vectors(s, VMXNET3_MAX_INTRS)) {
>>>> -            VMW_WRPRN("Failed to re-use MSI-X vectors");
>>>> -            msix_uninit(d, &s->msix_bar, &s->msix_bar);
>>>> -            s->msix_used = false;
>>>> -            return -1;
>>>> -        }
>>>> -    }
>>>> -
>>>>      vmxnet3_validate_queues(s);
>>>>      vmxnet3_validate_interrupts(s);
>>> 
>>> This hunk isn't obvious.  Can you explain the change?
>>> 
>> 
>> flag msix_used is used in VMStateDescription.post_Load().
>> 
>> 1st, I think msix's code here is not necessary, because in
>> destination, device has been realized before incoming migration, So I
>> don't know why re-use MSI-X vectors here. Dmitry, could help to
>> explain?
>> 
>> 2nd, this patch is going to remove this flag, so I removed the hunk.
> 
> We need to find out whether the call of vmxnet3_use_msix_vectors() is
> necessary.  I suspect it's not only not necessary, but actively wrong.
> 
> If that's true, removing becomes a bug fix that should be a separate
> patch.
> 
> If it's only unnecessary, the removal may stay in this patch, but it
> needs to be explained.  Separate patch might be easier to explain.  Your
> choice.
> 
> If it correct and necessary, then this patch needs to be changed not to
> drop it.  Instead, replace s->msix_used by msix_enabled(d) like you do
> elsewhere.
> 
> Dmitry, can you help us find out?

Hello,

Yes, from what I see, this call is wrong and leads to
reference leaks on device unload at migration target.
It should be removed.

Best regards,
Dmitry