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Date: Thu, 02 Sep 2010 18:05:39 +0200
From: Stefan Weil <weil@mail.berlios.de>
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Subject: Re: [Qemu-devel] [PATCH 2/7] pci: memory access API and IOMMU support
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To: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: kvm@vger.kernel.org, mst@redhat.com, joro@8bytes.org, qemu-devel@nongnu.org, blauwirbel@gmail.com, yamahata@valinux.co.jp, paul@codesourcery.com, avi@redhat.com

Am 02.09.2010 10:51, schrieb Eduard - Gabriel Munteanu:
> On Wed, Sep 01, 2010 at 10:10:30PM +0200, Stefan Weil wrote:
>    
>> Please see my comments at the end of this mail.
>>
>>
>> Am 30.08.2010 00:08, schrieb Eduard - Gabriel Munteanu:
>>      
>>> PCI devices should access memory through pci_memory_*() instead of
>>> cpu_physical_memory_*(). This also provides support for translation and
>>> access checking in case an IOMMU is emulated.
>>>
>>> Memory maps are treated as remote IOTLBs (that is, translation caches
>>> belonging to the IOMMU-aware device itself). Clients (devices) must
>>> provide callbacks for map invalidation in case these maps are
>>> persistent beyond the current I/O context, e.g. AIO DMA transfers.
>>>
>>> Signed-off-by: Eduard - Gabriel Munteanu<eduard.munteanu@linux360.ro>
>>> ---
>>>        
> [snip]
>
>    
>>> +static inline void pci_memory_read(PCIDevice *dev,
>>> + pcibus_t addr,
>>> + uint8_t *buf,
>>> + pcibus_t len)
>>> +{
>>> + pci_memory_rw(dev, addr, buf, len, 0);
>>> +}
>>> +
>>> +static inline void pci_memory_write(PCIDevice *dev,
>>> + pcibus_t addr,
>>> + const uint8_t *buf,
>>> + pcibus_t len)
>>> +{
>>> + pci_memory_rw(dev, addr, (uint8_t *) buf, len, 1);
>>> +}
>>> +
>>> #endif
>>>        
>> The functions pci_memory_read and pci_memory_write not only read
>> or write byte data but many different data types which leads to
>> a lot of type casts in your other patches.
>>
>> I'd prefer "void *buf" and "const void *buf" in the argument lists.
>> Then all those type casts could be removed.
>>
>> Regards
>> Stefan Weil
>>      
> I only followed an approach similar to how cpu_physical_memory_{read,write}()
> is defined. I think I should change both cpu_physical_memory_* stuff and
> pci_memory_* stuff, not only the latter, if I decide to go on that
> approach.
>
>
> 	Eduard
>    


Yes, cpu_physical_memory_read, cpu_physical_memory_write
and cpu_physical_memory_rw should be changed, too.

They also require several type casts today.

But this change can be done in an independent patch.

Stefan