Date: Sat, 18 Apr 2009 23:28:34 -0500 From: Nathan Whitehorn <nwhitehorn@freebsd.org> To: Andreas Tobler <andreast-list@fgznet.ch> Cc: FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: X11 CURRENT and non-altivec based macs Message-ID: <49EAA872.9010505@freebsd.org> In-Reply-To: <49EA4547.8010508@freebsd.org> References: <49EA2A57.1040100@fgznet.ch> <49EA4547.8010508@freebsd.org>
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Nathan Whitehorn wrote: > Andreas Tobler wrote: >> Hi all, >> >> I discovered a nasty issue which hits all non-altivec based ppc >> systems, mostly G3, there are some 7400 w/o altivec, which want to >> use X11. >> >> When you upgraded to -CURRENT and latest Xorg stuff including >> pixman-0.15.2 you'll hit a coredump when starting X with a >> recent/decent wm. >> >> Analyzing the coredump of Xorg led me to this: >> >> #0 0x21b9e494 in pixman_have_vmx () from >> /usr/local/lib/libpixman-1.so.9 Cannot find new threads: generic error >> >> A closer look into the build of pixman showed me that it was built >> with altivec support. No go on my G3. >> >> I helped myself with the below patch in the ports Makefile. But I do >> not know if the other ppc users 'have' real working Altivec support. >> We have Altivec support since a few moons in the kernel. Thanks Nathan! >> I know we build the kernel w/o Altivec. How do we want to build user >> applications/packages? Also w/o altivec or with? >> >> We can either adjust the ports Makefile or try to fixup the pixman >> sources. They are currently 'fixed' for apple and linux only. Fixed >> in terms of runtime detection of Altivec capability. (see >> pixman/pixman-pict.c) >> >> Do we have already a sysctl telling us we have altivec, I do not see >> such a sysctl? >> >> Suggestions? >> In case of disabling vmx on all ppc based systems, who do I need to >> ping, x11@freebsd.org? > Could you provide some more information than this (versions of X11, > pixman and name/version of the window manager)? I just tested the > non-Apple/non-Linux VMX detection code in pixman and it appears to > work properly. > > Providing a sysctl turned out to be problematic since PowerPC CPUs, > unlike x86, do not provide a features mask. You either have to have a > table of CPUs and capabilities, or try the instructions you want to > know about and see if you get SIGILL. We could do this in the kernel > and provide a sysctl, but you can do the more-portable SIGILL just as > easily from userspace, and this is what pixman currently does. I managed to reproduce this. There's something weird going on that I'll look into. Thanks for investigating! -Nathan
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