This patch fixed an intel-hda sound card emulation problem as follows:

http://lists.gnu.org/archive/html/qemu-devel/2013-01/msg05453.html

I found a bug that qemu doesn't support for setting master volume/mute when guest is winxp. but the wave volume in the volume control works fine.I don't know why it does.

And then the reporter submitted the patch, but not accepted by qemu mainline.

http://lists.gnu.org/archive/html/qemu-devel/2013-01/msg05452.html