On 12/03/11 13:02, Nilay Vaish wrote: > On Wed, 30 Nov 2011, Gabriel Michael Black wrote: > >> That may be the same thing that's happening with Ali's branch >> predictor patch. With Ruby execution changes enough to hit one of the >> broken squashing cases. The Ruby integration is probably working. >> >> Gabe >> >> Quoting Nilay Vaish <[email protected]>: >> >>> Gabe, when I boot FS with O3 CPU and Ruby, I get the following >>> output on the terminal of the simulated system. >>> >>> EXT2-fs warning: mounting unchecked fs, running e2fsck is recommended >>> VFS: Mounted root (ext2 filesystem). >>> Freeing unused kernel memory: 232k freed >>> init[1]: segfault at ffffffff802095c0 rip ffffffff802095c8 rsp >>> 00007fff38fa81b8 error 15 >>> init[1]: segfault at ffffffff802095c0 rip ffffffff802095c8 rsp >>> 00007fff38fa81b8 error 15 >>> >>> The segfault message keeps appearing. Do you know why this might be >>> happening? >>> > > Gabe, how can I confirm this? Is there something that I can do to > resolve the problem with branch prediction? > > Thanks > Nilay > _______________________________________________ > gem5-dev mailing list > [email protected] > http://m5sim.org/mailman/listinfo/gem5-dev
I'm fairly confident that's what's going on. The stack address is user space and the instruction pointer is in kernel space. The page fault is from near the ip, and the error code is 15 which means, if I'm not mistaken, a permission problem on fetch. You can't easily fix the problem, but if you want to get started the first step would be to clean up the squashing mechanisms in O3 like I brought up in that email a while ago. The real problem is that squashing doesn't always preserve enough state (the macroop instance specifically) in all situations, and that the squashing stuff is too ad-hoc and all over the place to really fix it correctly and know that it's correct. I'd thought I fixed it before when I fixed one particular squash path, but obviously I didn't get it all. Gabe _______________________________________________ gem5-dev mailing list [email protected] http://m5sim.org/mailman/listinfo/gem5-dev
