[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] change cd iso image in hvm but loop not changed?
On Mon, Jul 27, 2009 at 11:03 AM, Stefano Stabellini<stefano.stabellini@xxxxxxxxxxxxx> wrote: > On Sun, 26 Jul 2009, Andrew Lyon wrote: >> Hi, >> >> I booted a windows hvm with a iso image (/root/t.iso) connected to the >> cdrom, I then changed the iso image using the following technique: >> >> >> I used xm block-list <domid> to find the cdrom be-path: >> >> 5632 0 0 1 -1 -1 /local/domain/0/backend/vbd/3/5632 >> >> To make absolutely sure I got the right device I used xenstore-read: >> >> xenstore-read /local/domain/0/backend/vbd/3/5632/params >> >> /root/t.iso >> >> >> I then used xenstore-write to change the iso image: >> >> xenstore-write /local/domain/0/backend/vbd/3/5632/params >> /home/admin/isos/sql2k8.iso >> >> >> After a few seconds the new cd appears in windows, however there is >> still a loop device setup for the original iso image: >> >> losetup -a >> /dev/loop/0: [0802]:1517 (/root/t.iso) >> >> >> Why is this setup? if the cd can be changed without mounting the new >> iso as a loop device why do it in the first place? >> >> the hvm has gplpv drivers loaded but they do not provide cdrom, it is >> emulated. > > Qemu opens cdrom images directly using open and set a watch on params on > xenstore to recognize if someone changes the cdrom image and if it > happens it closes the old one and open the new one. > On the other hand the vbd backend for the cdrom is set by xend\hotplug scripts > at domain creation so it is never updated afterward. > If you have time to write a patch for xend to better handle cdrom > changes we would be glad to accept it :) > > I still dont understand why it is necessary to loopback mount the iso image if I can change it without the new image being loopback mounted, what is the loop device used for? Andy _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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