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Re: [Qemu-devel] Re: [PATCH] Disable O_DIRECT for physical CDROM/DVD dri
From: |
David S. Ahern |
Subject: |
Re: [Qemu-devel] Re: [PATCH] Disable O_DIRECT for physical CDROM/DVD drives |
Date: |
Tue, 20 Jul 2010 10:16:56 -0600 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100621 Fedora/3.0.5-1.fc13 Lightning/1.0b2pre Thunderbird/3.0.5 |
On 07/20/10 10:02, Jes Sorensen wrote:
> On 07/20/10 17:40, Anthony Liguori wrote:
>> 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?
>>
>> Silently disabling something a user explicitly asked for is not a good
>> option. In the very least, it should error out entirely.
>
> I thought about this, but it would require basically fixing up or
> copying all of the pread/pwrite code to use the right block size. This
> is really more of a band-aid but it should be pretty safe.
>
> Cheers,
> Jes
>
>
What about setting the logical and physical block size properties? Is
the intent of these to handle varying sizes amongst block devices?
David
Re: [Qemu-devel] Re: [PATCH] Disable O_DIRECT for physical CDROM/DVD drives, Kevin Wolf, 2010/07/20
Re: [Qemu-devel] [PATCH] Disable O_DIRECT for physical CDROM/DVD drives, Natalia Portillo, 2010/07/20