Red Hat Bugzilla – Bug 492866
Xen guest kernel advertises absolute mouse pointer feature which it is incapable of setting up correctly
Last modified: 2009-09-02 04:17:04 EDT
Description of problem:
The PVFB graphics driver includes a paravirt mouse input device. When talking to the host OS over xenbus, it advertises that it supports absolute coordinate mode. RHEL-5 userspace is incapable of actually running the mouse in absolute mode by default though, so out of the box the guest OS is doing abs -> rel coordinate conversion. This in turn causes problems for anyone connecting to the guest OS using the VNC server in the host OS because their mouse pointer will likely hit an invisible wall.
The absolute mouse coordinate feature should be disabled by default in RHEL-5 guest kernels. A boot parameter, or other tunable should be provided to allow absolute mode to be re-enabled if the admin has manually configured an xorg.conf that supports it.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Boot RHEL-5 guest
2. On host run xenstore-ls /local/domain/0/backend/vkbd
feature-abs-pointer = "1"
feature-abs-pointer = "0"
Xenstore node /local/domain/0/backend/vkbd shows whether the backend (host) offered the feature. To see whether the frontend (guest) accepted it, which is what you want here, you run
# xenstore-read /local/domain/$DOMID/device/vkbd/0/request-abs-pointer
Created attachment 339538 [details]
Change PVFB not to select abs. pointer by default
This patch makes the xenkbd driver reject absolute pointers, unless they
are enabled with kernel parameter xenkbd.abs_pointer=1.
You can download this test kernel from http://people.redhat.com/dzickus/el5
Please do NOT transition this bugzilla state to VERIFIED until our QE team
has sent specific instructions indicating when to do so. However feel free
to provide a comment indicating that this fix has been verified.
The original change was at the request of the TAM. I've knocked it down to high/high since the fix is at the ON_QA state.
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.