Re: [Qemu-devel] Re: [PATCH] Disable O_DIRECT for physical CDROM/DVD drives

[Kevin Wolf]

Am 20.07.2010 17:40, schrieb Anthony Liguori:
> On 07/20/2010 10:17 AM, address@hidden wrote:
>> From: Jes Sorensen<address@hidden>
>>
>> O_DIRECT (cache=none) requires sector alignment, however the physical
>> sector size of CDROM/DVD drives is 2048, as opposed to most disk
>> devices which use 512. QEMU is hard coding 512 all over the place, so
>> allowing O_DIRECT for CDROM/DVD devices does not work.
>>
>> Signed-off-by: Jes Sorensen<address@hidden>
>>    
> 
> Wouldn't a better solution be to have a cdrom_read/cdrom_write hook that 
> did the appropriate bouncing?

We already have code that does some bouncing, we'd just need to teach it
to use different sizes than 512. Duplicating everything wouldn't be a
nice solution.

> Silently disabling something a user explicitly asked for is not a good 
> option.  In the very least, it should error out entirely.

Yeah, that's probably better.

Kevin