Re: [Qemu-devel] [PATCH 1/1] ide: unify io_buffer_offset increments

[John Snow <jsnow@redhat.com>]

On 09/07/2015 12:37 PM, Paolo Bonzini wrote:
> 
> 
> On 26/08/2015 01:45, John Snow wrote:
>> IDEState's io_buffer_offset was originally added to keep track of offsets
>> in AHCI rather exclusively, but it was added to IDEState instead of an
>> AHCI-specific structure.
> 
> Interesting to see something weird turn into feature. :)
> 

There's lots of stuff in places where it doesn't really belong in the
IDE universe, so it takes a while to sift through all the usages and
start to straighten it all out.

> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> 

Grazie.

>> AHCI fakes all PIO transfers using DMA and a scatter-gather list. When
>> the core or atapi layers invoke HBA-specific mechanisms for transfers,
>> they do not always know that it is being backed by DMA or a sglist, so
>> this offset is not always updated by the HBA code everywhere.
>>
>> If we modify it in dma_buf_commit, however, any HBA that needs to use
>> this offset to manage operating on only part of a sglist will have
>> access to it.
>>
>> This will fix ATAPI PIO transfers performed through the AHCI HBA,
>> which were previously not modifying this value appropriately.
>>
>> This will fix ATAPI PIO transfers larger than one sector.
> 

Thanks, applied to my IDE tree:

https://github.com/jnsnow/qemu/commits/ide
https://github.com/jnsnow/qemu.git

--js