Am 08.02.2013 18:43, schrieb Stefan Weil: > Am 08.02.2013 13:14, schrieb Jeff Cody: >> 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"? > > Linux is a modern OS per definition :-) > > I made an additional test with Knoppix (from December 2006), > and it worked as expected.
So I'm afraid that the reason isn't the guest OS but the Virtual PC version. I guess supporting newer versions of it is more important, so if Jeff's testing passes, I'm not against taking the patch, even though I don't feel completely comfortable about it. But I don't see how we could support both ways at the same time. Kevin
