x86: handle PAT more like other CPU features
Impact: Cleanup
When PAT was originally introduced, it was handled specially for a few
reasons:
- PAT bugs are hard to track down, so we wanted to maintain a
whitelist of CPUs.
- The i386 and x86-64 CPUID code was not yet unified.
Both of these are now obsolete, so handle PAT like any other features,
including ordinary feature blacklisting due to known bugs.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/kernel/cpu/addon_cpuid_features.c b/arch/x86/kernel/cpu/addon_cpuid_features.c
index 2cf2363..4e581fd 100644
--- a/arch/x86/kernel/cpu/addon_cpuid_features.c
+++ b/arch/x86/kernel/cpu/addon_cpuid_features.c
@@ -143,37 +143,3 @@
return;
#endif
}
-
-#ifdef CONFIG_X86_PAT
-void __cpuinit validate_pat_support(struct cpuinfo_x86 *c)
-{
- if (!cpu_has_pat)
- pat_disable("PAT not supported by CPU.");
-
- switch (c->x86_vendor) {
- case X86_VENDOR_INTEL:
- /*
- * There is a known erratum on Pentium III and Core Solo
- * and Core Duo CPUs.
- * " Page with PAT set to WC while associated MTRR is UC
- * may consolidate to UC "
- * Because of this erratum, it is better to stick with
- * setting WC in MTRR rather than using PAT on these CPUs.
- *
- * Enable PAT WC only on P4, Core 2 or later CPUs.
- */
- if (c->x86 > 0x6 || (c->x86 == 6 && c->x86_model >= 15))
- return;
-
- pat_disable("PAT WC disabled due to known CPU erratum.");
- return;
-
- case X86_VENDOR_AMD:
- case X86_VENDOR_CENTAUR:
- case X86_VENDOR_TRANSMETA:
- return;
- }
-
- pat_disable("PAT disabled. Not yet verified on this CPU type.");
-}
-#endif
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 83492b1..0f86563 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -570,8 +570,6 @@
if (this_cpu->c_early_init)
this_cpu->c_early_init(c);
- validate_pat_support(c);
-
#ifdef CONFIG_SMP
c->cpu_index = boot_cpu_id;
#endif
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 8ea6929..20ce03a 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -50,6 +50,18 @@
set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
}
+ /*
+ * There is a known erratum on Pentium III and Core Solo
+ * and Core Duo CPUs.
+ * " Page with PAT set to WC while associated MTRR is UC
+ * may consolidate to UC "
+ * Because of this erratum, it is better to stick with
+ * setting WC in MTRR rather than using PAT on these CPUs.
+ *
+ * Enable PAT WC only on P4, Core 2 or later CPUs.
+ */
+ if (c->x86 == 6 && c->x86_model < 15)
+ clear_cpu_cap(c, X86_FEATURE_PAT);
}
#ifdef CONFIG_X86_32