Re: [PATCH 4/6] hw/dma: Replace alloc() + address_space_init() by address_space_create()

[Philippe Mathieu-Daudé]

On 8/19/21 4:38 PM, Peter Maydell wrote:
> On Thu, 19 Aug 2021 at 15:32, Philippe Mathieu-Daudé <philmd@redhat.com> 
> wrote:
>>
>> On 8/19/21 4:22 PM, Peter Maydell wrote:
>>> On Thu, 19 Aug 2021 at 15:21, Philippe Mathieu-Daudé <philmd@redhat.com> 
>>> wrote:
>>>>
>>>> Replace g_malloc0() + address_space_init() by address_space_create().
>>>> Release the resource in DeviceUnrealize().
>>>>
>>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>>> ---
>>>>  hw/dma/xlnx-zdma.c    | 15 +++++++++------
>>>>  hw/dma/xlnx_csu_dma.c |  9 ++-------
>>>>  2 files changed, 11 insertions(+), 13 deletions(-)
>>>>
>>>> diff --git a/hw/dma/xlnx-zdma.c b/hw/dma/xlnx-zdma.c
>>>> index fa38a556341..9f6b3fa47c6 100644
>>>> --- a/hw/dma/xlnx-zdma.c
>>>> +++ b/hw/dma/xlnx-zdma.c
>>>> @@ -777,15 +777,17 @@ static void zdma_realize(DeviceState *dev, Error 
>>>> **errp)
>>>>          };
>>>>      }
>>>>
>>>> -    if (s->dma_mr) {
>>>> -        s->dma_as = g_malloc0(sizeof(AddressSpace));
>>>> -        address_space_init(s->dma_as, s->dma_mr, NULL);
>>>> -    } else {
>>>> -        s->dma_as = &address_space_memory;
>>>> -    }
>>>> +    s->dma_as = address_space_create(s->dma_mr ?: get_system_memory(), 
>>>> NULL);
>>>>      s->attr = MEMTXATTRS_UNSPECIFIED;
>>>>  }
>>>
>>> Why are these devices doing a heap allocation rather than
>>> having an AddressSpace whatever field in their device struct ?
>>
>> To easily use &address_space_memory if 'memory' link is NULL?
> 
> They could do that with
>     AddressSpace our_as;
>     AddressSpace *dma_as;
> 
> and set dma_as to &s->our_as or &address_space_memory.
> 
> Or we could fix the two boards which create these devices to always
> pass in an MR to use for DMA and drop the conditionality.

Clever, thanks.