Re: [Qemu-devel] [PATCH 03/13] iommu: Add universal DMA helper functions

[Anthony Liguori <anthony@codemonkey.ws>]

On 06/20/2012 04:42 PM, Michael S. Tsirkin wrote:
> On Wed, Jun 20, 2012 at 04:38:30PM -0500, Anthony Liguori wrote:
>> On 06/20/2012 04:32 PM, Michael S. Tsirkin wrote:
>>> On Wed, Jun 20, 2012 at 04:16:47PM -0500, Anthony Liguori wrote:
>>>>> diff --git a/hw/pci.h b/hw/pci.h
>>>>> index 7f223c0..ee669d9 100644
>>>>> --- a/hw/pci.h
>>>>> +++ b/hw/pci.h
>>>>> @@ -558,10 +558,16 @@ static inline uint32_t pci_config_size(const PCIDevice *d)
>>>>>   }
>>>>>
>>>>>   /* DMA access functions */
>>>>> +static inline DMAContext *pci_dma_context(PCIDevice *dev)
>>>>> +{
>>>>> +    /* Stub for when we have no PCI iommu support */
>>>>> +    return NULL;
>>>>> +}
>>>>
>>>> Why is all of this stuff static inline?
>>>
>>> Let's face it, most people don't need an MMU in their VM.
>>> inline stubs help make double sure we are not adding
>>> overhead for the sake of this niche case.
>>
>> It also makes for an overly complex pci.h with no obvious performance justification.
>>
> A stub in a header plus an offline empty function is even more useless
> code. inline stubs is standard procedure.

Look at 8/13.  They don't stay stubs for long.

Regards,

Anthony Liguori

>
>> Let's not prematurely optimize here.
>>
>> Regards,
>>
>> Anthony Liguori
>
> It's not just an optimization.  It is easier to see what's going on this
> way.
>