[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] Question about total_sectors in block/vpc.c
From: |
Christoph Hellwig |
Subject: |
Re: [Qemu-devel] Question about total_sectors in block/vpc.c |
Date: |
Mon, 11 Apr 2011 20:14:17 +0200 |
User-agent: |
Mutt/1.5.17 (2007-11-01) |
On Sat, Apr 09, 2011 at 09:05:41PM +0100, Stefan Hajnoczi wrote:
> On Sat, Apr 9, 2011 at 5:51 PM, Lyu Mitnick <address@hidden> wrote:
> > Hell all,
> > I have take a look of block/vpc.c and meet a question in vpc_create().?At
> > the line
> > 550, the code is:
> > total_sectors = options->value.n / 512;
> > I am wondering whether the size between?total_sectors * 512
> > and?options->value.n
> > would be discard.
>
> Yes, it rounds down. This reflects the assumption that a block device
> cannot be addressed below 512 byte sectors. Because of this block
> devices size must be a multiple of 512 bytes.
>
> I think a reasonable protection would be to have block.c:bdrv_create()
> fail if size is not a multiple of BDRV_SECTOR_SIZE. This way other
> image formats are protected too.
There are block devices that aren't alignment to 512 bytes. Audio CDROMs are
the most prominent example, or AS/400 disks. I don't think these matter for
emulation, but if we'd ever implement DIF/DIX emulation inside qemu we'd
have to store the protection information somewhere. It still wouldn't
work with existing disk format, so adding the above check into the formats
bdrv_create routines sounds fine, but doing it in the core block code
might not be an overly smart idea.
- [Qemu-devel] Question about total_sectors in block/vpc.c, Lyu Mitnick, 2011/04/09
- Re: [Qemu-devel] Question about total_sectors in block/vpc.c, Stefan Hajnoczi, 2011/04/09
- Re: [Qemu-devel] Question about total_sectors in block/vpc.c, Lyu Mitnick, 2011/04/10
- Re: [Qemu-devel] Question about total_sectors in block/vpc.c, Stefan Hajnoczi, 2011/04/11
- Re: [Qemu-devel] Question about total_sectors in block/vpc.c, Lyu Mitnick, 2011/04/13
- Re: [Qemu-devel] Question about total_sectors in block/vpc.c, Kevin Wolf, 2011/04/14
- Re: [Qemu-devel] Question about total_sectors in block/vpc.c, Lyu Mitnick, 2011/04/15
- Re: [Qemu-devel] Question about total_sectors in block/vpc.c, Kevin Wolf, 2011/04/18
Re: [Qemu-devel] Question about total_sectors in block/vpc.c,
Christoph Hellwig <=