[SeaBIOS] [PATCH] fix two issues with virtio-blk

[Sebastian Herbszt]

Kevin O'Connor wrote:
> On Sun, May 16, 2010 at 11:08:57AM +0300, Gleb Natapov wrote:
>> On Sat, May 15, 2010 at 05:17:31PM +0200, Sebastian Herbszt wrote:
>> > What the BIOS should do or not doesn't seem to be defined anywhere (yet).
>> > Current drives with physical sector size > 512 bytes report a logical sector
>> > size of 512 bytes and do the emulation on their own. The BIOS doesn't need
>> > to be modified so far to support those drives. If drives with logical sector
>> > size > 512 bytes appear this situation might change. Doing a read emulation
>> Isn't it chicken n' egg situation. If BIOSes will not add 4K block support
>> drives will never be able to use 4K logical blocks.
> 
> It was my understanding that new drives will start up in an emulation
> mode which uses 512 byte sectors.  Later on the OS can activate the
> native sector size.

AFAIK that "activate" doesn't exist. It starts in emulation mode and stays there.
I was suggesting something like that "activate" in my other reply, but i don't think
that's available (yet).

Sebastian

> This also raises a possibility for virtio - maybe a new command or
> flag could be added to temporarily support 512 byte reads.  Thus the
> main OS wont be penalized, and the bios wont have to emulate the reads
> (the host will do it instead).  That said, I'm not against a patch
> which generalizes the SeaBIOS cdemu block conversion code for virtio
> if you wish to do that.  (It will reserve more memory, but I doubt
> anyone using virtio will care.)
> 
> -Kevin