On Wed, 2016-03-09 at 13:53 -0500, Bruce Ashfield wrote: > On 2016-03-01 8:41 PM, Paul Gortmaker wrote: > > [Re: [poky] [PATCH 1/1] poky: update qemu* to prefer 4.4 kernel] On > > 13/02/2016 (Sat 17:17) Richard Purdie wrote: > > > > > I'm moving the discussion to OE-Core and pulling in some kernel > > > people. > > > I think I understand what is wrong and how to fix it but I could > > > use > > > someone who actually knows this code. > > > > > > To summarise the story so far, on qemux86, X doesn't start and > > > there is > > > a backtrace in the logs: > > > > > > x86/PAT: Xorg:705 map pfn expected mapping type uncached-minus > > > for [mem 0xfd000000-0xfdffffff], got write-combining > > > > So Bruce helped me set up a reproducer locally today since he'd > > already > > invested the time on that, and then I boiled that down to divorce > > it > > from the slower steps of build-deploy-boot to make the bisect > > something > > that mortal humans could tolerate. > > > > Amusingly enough that led to: > > > > commit 9cd25aac1f44f269de5ecea11f7d927f37f1d01c > > Author: Borislav Petkov <b...@suse.de> > > Date: Thu Jun 4 18:55:10 2015 +0200 > > > > x86/mm/pat: Emulate PAT when it is disabled > > > > So while some of us were joking on IRC about the validity of > > forcibly > > disabling PAT (via cmdline or Kconfig) as a workaround, the one > > line > > shortlog above tells us that it wasn't so off the mark after all. > > > > Bruce and I will decide what to do with this tomorrow, but since > > Richard > > spent so much time on it, I thought he'd like to know this in the > > interim. Good times. :-/ > > As another follow up. The thread can be summarized as "It doesn't > look like it should have worked before, and qemu's pat emulation > may be the issue'. > > The suggestion is to run with 'nopat', which is what Richard > originally > did. > > So I'm going to prep a patch that drops the kernel patch, and leaves > nopat enabled on the qemu command line. That should get us put back > together in a semi-permanent way.
How sure are we this is a bug in QEMU's pat emulation? If that is the case we should file a bug against qemu and try and fix it rather than work around it... Cheers, Richard -- _______________________________________________ Openembedded-core mailing list Openembedded-core@lists.openembedded.org http://lists.openembedded.org/mailman/listinfo/openembedded-core
