* Add an enablepat boot parameter, useful for testing CPUs not yet
added to the whitelist.
* Don't try to enable PAT if it was never enabled in the first place.
Signed-off-by: Dave Jones <davej@redhat.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 72c07a0..e179c22 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -236,6 +236,10 @@ and is between 256 and 4096 characters. It is defined in the file
try_unsupported: try to drive unsupported chipsets
(may crash computer or cause data corruption)
+ enablepat [i386,x86-64]
+ Force the CPU's PAT feature to be used even if it
+ isn't in the kernels whitelist.
+
enable_timer_pin_1 [i386,x86-64]
Enable PIN 1 of APIC timer
Can be useful to work around chipset bugs
diff --git a/arch/x86/kernel/cpu/addon_cpuid_features.c b/arch/x86/kernel/cpu/addon_cpuid_features.c
index c2e1ce3..6ce3202 100644
--- a/arch/x86/kernel/cpu/addon_cpuid_features.c
+++ b/arch/x86/kernel/cpu/addon_cpuid_features.c
@@ -50,9 +50,28 @@ void __cpuinit init_scattered_cpuid_features(struct cpuinfo_x86 *c)
}
}
+static int forcepat;
+
+static int __init x86_forcepat_setup(char *s)
+{
+ forcepat = 1;
+ return 1;
+}
+__setup("enablepat", x86_forcepat_setup);
+
+
#ifdef CONFIG_X86_PAT
void __cpuinit validate_pat_support(struct cpuinfo_x86 *c)
{
+ if (!test_cpu_cap(c, X86_FEATURE_PAT))
+ return;
+
+ if (forcepat == 1) {
+ printk(KERN_INFO "Force enabling PAT\n");
+ set_cpu_cap(c, X86_FEATURE_PAT);
+ return;
+ }
+
switch (c->x86_vendor) {
case X86_VENDOR_AMD:
if (c->x86 >= 0xf && c->x86 <= 0x11)
--
