This updates the qcow2 specification to cover version 3. It contains the
following changes:
- Added compatible/incompatible/auto-clear feature bits plus an optional
feature name table to allow useful error messages even if an older
version doesn't know some feature at all.
- Configurable refcount width. If you don't want to use internal
snapshots, make refcounts one bit and save cache space and I/O.
- Zero cluster flags. This allows discard even with a backing file that
doesn't contain zeros. It is also useful for copy-on-read/image
streaming, as you'll want to keep sparseness without accessing the
remote image for an unallocated cluster all the time.
- Fixed internal snapshot metadata to use 64 bit VM state size. You
can't save a snapshot of a VM with >= 4 GB RAM today.
- Extended internal snapshot metadata to contain the disk size, so that
resizing images that have snapshots can be allowed in the future.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The PCI hotplug eject register has always returned 0, so let's redefine
it as a hotplug feature register. The existing model of using separate
up & down read-only registers and an eject via write to this register
becomes the base implementation. As we make use of new interfaces we'll
set bits here to allow the BIOS and AML implementation to optimize for
the platform implementation.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Clarify this register as read-only and remove write code. No
change in existing behavior.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The write side of these registers is never used and actually can't be
used as defined because any read/modify/write sequence from the guest
potentially races with qemu. Drop the write support and define these
as read-only registers.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The official spelling is QEMU.
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
Zero data clusters are a space-efficient way of storing zeroed regions
of the image.
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This adds a description of the qcow2 file format to the docs/ directory.
Besides documenting what's there, which is never wrong, the document should
provide a good basis for the discussion of format extensions (called "qcow3"
in previous discussions)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Document how QEMU communicates with ACPI BIOS for PCI hotplug.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
For some reason the carets ('^') in the QED specification disappeared.
This patch puts them back.
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
