On Fri, Feb 08, 2013 at 07:14:33AM -0500, Jeff Cody wrote: > On Fri, Feb 08, 2013 at 09:38:47AM +0100, Kevin Wolf wrote: > > Am 07.02.2013 20:26, schrieb Stefan Weil: > > > From: Stefan Weil <stefan@kiwi.(none)> > > > > > > The size calculated from the CHS values is not the real image (disk) size, > > > but usually a smaller value. This is caused by rounding effects. > > > > > > Only older operating systems use CHS. Such guests won't be able to use > > > the whole disk. All modern operating systems use the real size. > > > > > > This patch fixes https://bugs.launchpad.net/qemu/+bug/1105670/. > > > > > > Signed-off-by: Stefan Weil <s...@weilnetz.de> > > > --- > > > > > > This is a rebased extract from my patch series for block/vpc.c. > > > It's the minimum needed to fix the open bug for QEMU 1.4. > > > > > > The rest of the series can be discussed and applied after 1.4. > > > > > > Regards > > > > > > Stefan W. > > > > > > PS. Please excuse a previous personal mail which I had sent > > > with a wrong signature and without addressing qemu-devel. > > > > > > block/vpc.c | 14 +++++++++----- > > > 1 file changed, 9 insertions(+), 5 deletions(-) > > > > > > diff --git a/block/vpc.c b/block/vpc.c > > > index 82229ef..b4ff564 100644 > > > --- a/block/vpc.c > > > +++ b/block/vpc.c > > > @@ -34,6 +34,8 @@ > > > > > > #define HEADER_SIZE 512 > > > > > > +#define VHD_SECTOR_SIZE 512 > > > + > > > //#define CACHE > > > > > > enum vhd_type { > > > @@ -204,11 +206,13 @@ static int vpc_open(BlockDriverState *bs, int flags) > > > /* Write 'checksum' back to footer, or else will leave it with zero. > > > */ > > > footer->checksum = be32_to_cpu(checksum); > > > > > > - // The visible size of a image in Virtual PC depends on the geometry > > > - // rather than on the size stored in the footer (the size in the > > > footer > > > - // is too large usually) > > > - bs->total_sectors = (int64_t) > > > - be16_to_cpu(footer->cyls) * footer->heads * footer->secs_per_cyl; > > > + /* The visible size of a image in Virtual PC depends on the guest: > > > + * QEMU and other emulators report the real size (here in sectors). > > > + * All modern operating systems use this real size. > > > + * Very old operating systems use CHS values to calculate the total > > > size. > > > + * This calculated size is usually smaller than the real size. > > > + */ > > > + bs->total_sectors = be64_to_cpu(footer->size) / VHD_SECTOR_SIZE; > > > > It's unfortunate that I don't have my old Virtual PC installation around > > any more so I could prove that you're wrong for at least some versions. > > Or does a Linux of 2009 already count as "very old"? > > > > If we want to commit this - and I still feel uncomfortable about it - > > then maybe it's best to remove the comment altogether instead of making > > such claims. The new code is the intuitively expected one anyway. > > > > Kevin > > Kevin, > > I can test this on Virtual PC on a Win 7 install, as well as > Hyper-V (I've already tested the equivalent of this patch on Hyper-V > on Windows Server 2012). I'll do some testing today with this - if > you have anything in particular you want me to look at, just let me > know.
Hi Jeff, Thanks for testing this on your Virtual PC and Hyper-V setup. I'll merge this patch once you have confirmed your results. Stefan