On Wed, Mar 24, 2010 at 05:12:55PM +0200, Avi Kivity wrote: > On 03/24/2010 05:01 PM, Joerg Roedel wrote: >> $ cd /sys/kvm/guest0 >> $ ls -l >> -r-------- 1 root root 0 2009-08-17 12:05 name >> dr-x------ 1 root root 0 2009-08-17 12:05 fs >> $ cat name >> guest0 >> $ # ... >> >> The fs/ directory is used as the mount point for the guest root fs. > > The problem is /sys/kvm, not /sys/kvm/fs. I am not tied to /sys/kvm. We could also use /proc/<pid>/kvm/ for example. This would keep anything in the process space (except for the global list of VMs which we should have anyway). >> What I meant was: perf-kernel puts the guest-name into every sample and >> perf-userspace accesses /sys/kvm/guest_name/fs/ later to resolve the >> symbols. I leave the question of how the guest-fs is exposed to the host >> out of this discussion. We should discuss this seperatly. > > How I see it: perf-kernel puts the guest pid into every sample, and > perf-userspace uses that to resolve to a mountpoint served by fuse, or > to a unix domain socket that serves the files. We need a bit more information than just the qemu-pid, but yes, this would also work out. >> If a vm breaks into qemu it can access the host file system which is the >> bigger problem. In this case there is no isolation anymore. From that >> context it can even kill other VMs of the same user independent of a >> hypothetical /sys/kvm/. > > It cannot. sVirt labels the disk image and other files qemu needs with > the appropriate label, and everything else is off limits. Even if you > run the guest as root, it won't have access to other files. See my reply to Daniel's email. >> Yes, but its different from the implementation point-of-view. For the >> user it surely all plays together. > > We need qemu to cooperate for mmio tracing, and we can cooperate with > qemu for symbol resolution. If it prevents adding another kernel API, > that's a win from my POV. Thats true. Probably qemu can inject this information in the kvm-trace-events stream. Joerg -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
