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| H A D | vpc.c | 690cbb09 Tue Mar 03 10:41:54 GMT 2015 Peter Lieven <pl@kamp.de> block/vpc: make calculate_geometry spec conform
The VHD spec [1] allows for total_sectors of 65535 x 16 x 255 (~127GB)
represented by a CHS geometry. If total_sectors is greater
than 65535 x 16 x 255 this geometry is set as a maximum.
Qemu, Hyper-V and disk2vhd use this special geometry as an indicator
to use the image current size from the footer as disk size.
This patch changes vpc_create to effectively calculate a CxHxS geometry
for the given image size if possible while rounding up if necessary.
If the image size is too big to be represented in CHS we set the maximum
and write the exact requested image size into the footer.
This partly reverts commit 258d2edb, but leaves support for >127G disks
intact.
[1] http://download.microsoft.com/download/f/f/e/ffef50a5-07dd-4cf8-aaa3-442c0673a029/Virtual%20Hard%20Disk%20Format%20Spec_10_18_06.doc
Signed-off-by: Peter Lieven <pl@kamp.de>
Message-id: 1425379316-19639-4-git-send-email-pl@kamp.de
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
258d2edb Wed Oct 31 02:59:32 GMT 2012 Charles Arnold <carnold@suse.com> block: vpc support for ~2 TB disks
The VHD specification allows for up to a 2 TB disk size. The current
implementation in qemu emulates EIDE and ATA-2 hardware which only allows
for up to 127 GB. This disk size limitation can be overridden by allowing
up to 255 heads instead of the normal 4 bit limitation of 16. Doing so
allows disk images to be created of up to nearly 2 TB. This change does
not violate the VHD format specification nor does it change how smaller
disks (ie, <=127GB) are defined.
[Charles Arnold also writes: "In analyzing a 160 GB VHD fixed disk image
created on Windows 2008 R2, it appears that MS is also ignoring the CHS
values in the footer geometry field in whatever driver they use for
accessing the image. The CHS values are set at 65535,16,255 which
obviously doesn't represent an image size of 160 GB." -- Stefan]
Signed-off-by: Charles Arnold <carnold@suse.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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