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cbed27cdf0
In the file arch/x86/mm/pat.c, there's a '__pat_enabled' variable. The variable is set to 1 by default and the function pat_init() sets __pat_enabled to 0 if the CPU doesn't support PAT. However, on AMD K6-3 CPUs, the processor initialization code never calls pat_init() and so __pat_enabled stays 1 and the function pat_enabled() returns true, even though the K6-3 CPU doesn't support PAT. The result of this bug is that a kernel warning is produced when attempting to start the Xserver and the Xserver doesn't start (fork() returns ENOMEM). Another symptom of this bug is that the framebuffer driver doesn't set the K6-3 MTRR registers: x86/PAT: Xorg:3891 map pfn expected mapping type uncached-minus for [mem 0xe4000000-0xe5ffffff], got write-combining ------------[ cut here ]------------ WARNING: CPU: 0 PID: 3891 at arch/x86/mm/pat.c:1020 untrack_pfn+0x5c/0x9f ... x86/PAT: Xorg:3891 map pfn expected mapping type uncached-minus for [mem 0xe4000000-0xe5ffffff], got write-combining To fix the bug change pat_enabled() so that it returns true only if PAT initialization was actually done. Also, I changed boot_cpu_has(X86_FEATURE_PAT) to this_cpu_has(X86_FEATURE_PAT) in pat_ap_init(), so that we check the PAT feature on the processor that is being initialized. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luis R. Rodriguez <mcgrof@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Toshi Kani <toshi.kani@hp.com> Cc: stable@vger.kernel.org # v4.2+ Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1704181501450.26399@file01.intranet.prod.int.rdu2.redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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