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, jes.soren...@redhat.com wrote: >>> From: Jes Sorensen<jes.soren...@redhat.com> >>> >>> 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<jes.soren...@redhat.com> >>> >> >> 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
