new hope to get a standard Trusty Tahr kernel, that plays well with Pentium M

Nio Wiklund nio.wiklund at gmail.com
Thu Feb 27 10:14:24 UTC 2014


Hi,

Linked to from the Launchpad bug report

https://bugs.launchpad.net/bugs/930447

--- start quote ---
Date	Tue, 25 Feb 2014 13:01:47 +0700
From	Chris Bainbridge <>
Subject	[PATCH] x86: set Pentium M as PAE capable
	

Pentium M is PAE capable but does not indicate so in the CPUID response.
This is an issue now that some distributions are no longer shipping
non-PAE kernels (those distributions no longer boot on Pentium M). This
small patch fixes the issue by forcing the PAE capability on Pentium M.

For more discussion see https://bugs.launchpad.net/baltix/+bug/930447

Signed-off-by: Chris Bainbridge <chris.bainbridge at gmail.com>

---
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index bbe1b8b..97996aa 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -226,6 +226,12 @@ static void intel_workarounds(struct cpuinfo_x86 *c)
 		clear_cpu_cap(c, X86_FEATURE_SEP);

 	/*
+	 * PAE CPUID bug: Pentium M reports no PAE but has PAE
+	 */
+	if ((c->x86 == 6) && ((c->x86_model == 9) || (c->x86_model == 13)))
+		set_cpu_cap(c, X86_FEATURE_PAE);
+
+	/*
 	 * P4 Xeon errata 037 workaround.
 	 * Hardware prefetcher may cause stale data to be loaded into the cache.
 	 */
--- end quote ---

I think and hope this indicates, that we'll get a standard Trusty Tahr
kernel, that can be installed in Pentium M computers without fake-PAE.

Best regards
Nio



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