On 07/25/2017 09:41 AM, Peter Lieven wrote: > Signed-off-by: Peter Lieven <p...@kamp.de> > --- > docs/interop/qcow2.txt | 51 > +++++++++++++++++++++++++++++++++++++++++++++++++- > roms/ipxe | 2 +- > 2 files changed, 51 insertions(+), 2 deletions(-) >
> + > +== Compress format extension == > + > +The compress format extension is an optional header extension. It provides > +the ability to specify the compress algorithm and compress parameters s/the compress algorithm/the compression algorithm/ > +that are used for compressed clusters. This new header MUST be present if > +the incompatible-feature bit "compress format bit" is set and MUST be absent > +otherwise. > + > +The fields of the compress format extension are: > + > + Byte 0 - 13: compress_format_name (padded with zeros, but not > + necessarily null terminated if it has full length). > + Valid compression format names currently are: > + > + deflate: Standard zlib deflate compression without > + compression header Why did you name it "deflate" instead of "zlib" again? > + > + 14: compress_level (uint8_t) > + > + 0 = default compress level (valid for all formats, > default) > + > + Additional valid compression levels for deflate > compression: > + > + All values between 1 and 9. 1 gives best speed, 9 gives > best > + compression. The default compression level is defined by > zlib > + and currently defaults to 6. > + > + 15: compress_window_size (uint8_t) > + > + Window or dictionary size used by the compression format. > + Currently only used by the deflate compression algorithm. What must this be set to for other algorithms? I guess we get to that in later patches. > + > + Valid window sizes for deflate compression range from 8 to > + 15 inclusively. > + > +Note: Omitting the incompatible "Compress format bit" results in the usage > +of deflate compression with default compression level and a window size of 12 > +(which was default before QEMU 2.11). If exactly these parameters are choosen s/choosen/chosen,/ > +it is free to the implementation to omit the "Compress format bit" and the s/it is free to the implementation to omit/the implementation may omit/ > +compress format extension when updating the QCOW2 header. > + > + > == Host cluster management == > > qcow2 manages the allocation of host clusters by maintaining a reference > count > diff --git a/roms/ipxe b/roms/ipxe > index 0600d3a..b991c67 160000 > --- a/roms/ipxe > +++ b/roms/ipxe > @@ -1 +1 @@ > -Subproject commit 0600d3ae94f93efd10fc6b3c7420a9557a3a1670 > +Subproject commit b991c67c1d91574ef22336cc3a5944d1e63230c9 Oops. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
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