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Diffstat (limited to 'arch')
-rw-r--r--arch/x86/boot/cpucheck.c20
-rw-r--r--arch/x86/kernel/cpu/intel.c19
2 files changed, 39 insertions, 0 deletions
diff --git a/arch/x86/boot/cpucheck.c b/arch/x86/boot/cpucheck.c
index 100a9a10076a..f0d0b20fe149 100644
--- a/arch/x86/boot/cpucheck.c
+++ b/arch/x86/boot/cpucheck.c
@@ -67,6 +67,13 @@ static int is_transmeta(void)
cpu_vendor[2] == A32('M', 'x', '8', '6');
}
+static int is_intel(void)
+{
+ return cpu_vendor[0] == A32('G', 'e', 'n', 'u') &&
+ cpu_vendor[1] == A32('i', 'n', 'e', 'I') &&
+ cpu_vendor[2] == A32('n', 't', 'e', 'l');
+}
+
/* Returns a bitmask of which words we have error bits in */
static int check_cpuflags(void)
{
@@ -153,6 +160,19 @@ int check_cpu(int *cpu_level_ptr, int *req_level_ptr, u32 **err_flags_ptr)
asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
err = check_cpuflags();
+ } else if (err == 0x01 &&
+ !(err_flags[0] & ~(1 << X86_FEATURE_PAE)) &&
+ is_intel() && cpu.level == 6 &&
+ (cpu.model == 9 || cpu.model == 13)) {
+ /* PAE is disabled on this Pentium M but can be forced */
+ if (cmdline_find_option_bool("forcepae")) {
+ puts("WARNING: Forcing PAE in CPU flags\n");
+ set_bit(X86_FEATURE_PAE, cpu.flags);
+ err = check_cpuflags();
+ }
+ else {
+ puts("WARNING: PAE disabled. Use parameter 'forcepae' to enable at your own risk!\n");
+ }
}
if (err_flags_ptr)
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 34bbb555e269..897d6201ef10 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -186,6 +186,14 @@ static void intel_smp_check(struct cpuinfo_x86 *c)
}
}
+static int forcepae;
+static int __init forcepae_setup(char *__unused)
+{
+ forcepae = 1;
+ return 1;
+}
+__setup("forcepae", forcepae_setup);
+
static void intel_workarounds(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_X86_F00F_BUG
@@ -214,6 +222,17 @@ static void intel_workarounds(struct cpuinfo_x86 *c)
clear_cpu_cap(c, X86_FEATURE_SEP);
/*
+ * PAE CPUID issue: many Pentium M report no PAE but may have a
+ * functionally usable PAE implementation.
+ * Forcefully enable PAE if kernel parameter "forcepae" is present.
+ */
+ if (forcepae) {
+ printk(KERN_WARNING "PAE forced!\n");
+ set_cpu_cap(c, X86_FEATURE_PAE);
+ add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_NOW_UNRELIABLE);
+ }
+
+ /*
* P4 Xeon errata 037 workaround.
* Hardware prefetcher may cause stale data to be loaded into the cache.
*/