Re: [Qemu-trivial] [PATCH 1/1] virtio: pass argument by value for virtqueue_map_iovec()

[Paolo Bonzini]

On 05/11/2018 09:40, Laurent Vivier wrote:
> CC: Paolo as the use of modified num_sg has been removed by his patch:
> 
>   3b3b062821 virtio: slim down allocation of VirtQueueElements

Indeed, virtqueue_map and virtqueue_map_iovec are only used on migration
now, and that path does not need to modify *num_sg.  After my patch
virtqueue_pop calls virtqueue_map_desc instead of virtqueue_map (and
virtqueue_map_desc does need an in-out argument).

Reviewed-by: Paolo Bonzini <address@hidden>

Paolo

> On 02/11/2018 07:16, Dongli Zhang wrote:
>> Pass num_sg by value instead of by pointer, as num_sg is never modified in
>> virtqueue_map_iovec().
>>
>> Signed-off-by: Dongli Zhang <address@hidden>
>> ---
>>  hw/virtio/virtio.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>> index 4136d23..a5cb4e6 100644
>> --- a/hw/virtio/virtio.c
>> +++ b/hw/virtio/virtio.c
>> @@ -796,13 +796,13 @@ static void virtqueue_undo_map_desc(unsigned int 
>> out_num, unsigned int in_num,
>>  }
>>  
>>  static void virtqueue_map_iovec(VirtIODevice *vdev, struct iovec *sg,
>> -                                hwaddr *addr, unsigned int *num_sg,
>> +                                hwaddr *addr, unsigned int num_sg,
>>                                  int is_write)
>>  {
>>      unsigned int i;
>>      hwaddr len;
>>  
>> -    for (i = 0; i < *num_sg; i++) {
>> +    for (i = 0; i < num_sg; i++) {
>>          len = sg[i].iov_len;
>>          sg[i].iov_base = dma_memory_map(vdev->dma_as,
>>                                          addr[i], &len, is_write ?
>> @@ -821,8 +821,8 @@ static void virtqueue_map_iovec(VirtIODevice *vdev, 
>> struct iovec *sg,
>>  
>>  void virtqueue_map(VirtIODevice *vdev, VirtQueueElement *elem)
>>  {
>> -    virtqueue_map_iovec(vdev, elem->in_sg, elem->in_addr, &elem->in_num, 1);
>> -    virtqueue_map_iovec(vdev, elem->out_sg, elem->out_addr, &elem->out_num, 
>> 0);
>> +    virtqueue_map_iovec(vdev, elem->in_sg, elem->in_addr, elem->in_num, 1);
>> +    virtqueue_map_iovec(vdev, elem->out_sg, elem->out_addr, elem->out_num, 
>> 0);
>>  }
>>  
>>  static void *virtqueue_alloc_element(size_t sz, unsigned out_num, unsigned 
>> in_num)
>>
>