Bug 370431 - PVFB frontend can send bogus screen updates
PVFB frontend can send bogus screen updates
Product: Red Hat Enterprise Linux 4
Classification: Red Hat
Component: kernel-xen (Show other bugs)
All Linux
low Severity high
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Assigned To: Chris Lalancette
Martin Jenner
Depends On: 370341
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Reported: 2007-11-07 16:52 EST by Chris Lalancette
Modified: 2010-08-11 11:14 EDT (History)
2 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2008-02-24 13:49:28 EST
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
Copy of dirty patch from the RHEL-5.1 BZ (824 bytes, patch)
2007-11-07 16:53 EST, Chris Lalancette
no flags Details | Diff

  None (edit)
Description Chris Lalancette 2007-11-07 16:52:12 EST
+++ This bug was initially created as a clone of Bug #370341 +++

+++ This bug was initially created as a clone of Bug #368931 +++

Description of problem:

When using 'xm create' to start a paravirt guest, the SDL window often
disappears part way through the boot.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. Configure a pv guest to use SDL graphics
2. xm create <pv guest>
3. wait for the guest to boot all the way up
Actual results:
I've seen the SDL window disappear on both i386 and ia64 about 20% of the time. 
I see nothing suspicious in xend.log. There is no output to xend-debug.log.

Expected results:
The SDL window should remain present every time a paravirt guest is started.

Additional info:

Looks similar to bz# 217635

-- Additional comment from berrange@redhat.com on 2007-11-07 10:52 EST --
Co-incidentally yesterday i discovered a potential bug in the guest kernel PVFB
driver. It occassionally sends a framebuffer update event to the Dom0 with a x,y
of MAX_INT, MAX_INT, and a width+height of -MAX_INT, -MAX_INT.   When SDL then
tries to process this update event it gets an BadValue error from Xorg and
quits. In my tests against xen-unstable this happened on as many as 30% of all
bootup attempts with SDL, so I think its reasonably likely this is the same
problem you're describing. The VNC display doesn't seem to be affected, since
its update routine does region clipping. 

-- Additional comment from pm-rhel@redhat.com on 2007-11-07 10:54 EST --
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux maintenance release.  Product Management has requested
further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed
products.  This request is not yet committed for inclusion in an Update

-- Additional comment from armbru@redhat.com on 2007-11-07 16:22 EST --
Created an attachment (id=250871)
Fix tracking of screen dirtiness

The PVFB front end can get confused and send a bogus screen update to the back
end when the screen is clean.

Since the RHEL-4 fbfront stuff is based on the RHEL-5 stuff, I'm pretty sure it
has the same bug.  Cloning.
Comment 1 Chris Lalancette 2007-11-07 16:53:16 EST
Created attachment 250951 [details]
Copy of dirty patch from the RHEL-5.1 BZ
Comment 2 Bill Burns 2008-01-05 09:12:24 EST
Set dev ack for Chris Lalancette.
Comment 3 Chris Lalancette 2008-02-24 13:49:28 EST
Duh.  I should have looked at the RHEL-4 code before I opened this bug.  It
seems that I based RHEL-4 on a slightly newer version of the xenfb stuff than
what was in RHEL-5, and it already has this fix.  Closing this as NOTABUG.

Chris Lalancette
Comment 4 Chris Lalancette 2010-07-19 09:21:23 EDT
Clearing out bogus flag for reporting purposes.

Chris Lalancette

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