Re: [ANNOUNCE] kvm-14 release

Anthony Liguori
2007-02-22T17:25:51Z

Avi Kivity wrote:
> Laurent Vivier wrote:
>> There are remaining issues : libposix-aio uses kernel AIO, so files
>> must be
>> opened using O_DIRECT and buffers must be aligned. libposix-aio is
>> able to
>> manage other cases but this has a performance cost.
>>
>>
>
> Because the guest is also doing dma, the buffers are expected to be
> aligned (it might be different if using pio, but unlikely).

The IDE emulation always uses a temporary buffer. This is partially
because you cannot always rely on being able to use an offset on
phys_ram_base (when doing user only emulation).

We can pretty easily patch this code though to use the DMA address
directly instead of the temporary buffer in the non PIO case. We still
have to define a raw_pread() that is capable of emulating sector
alignment though since Linux will use PIO at first.

Regards,

Anthony Liguori