From 75a048119e76540d73132cfc8e0fa0c0a8bb6c83 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Thu, 22 Jan 2009 16:17:05 -0800 Subject: 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 --- arch/x86/kernel/cpu/intel.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'arch/x86/kernel/cpu/intel.c') diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 8ea6929e974..20ce03acf04 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -50,6 +50,18 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) 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 -- cgit v1.2.3 From 30a0fb947a68ad3ab8a7184e3b3d79dce10e3688 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Mon, 26 Jan 2009 09:40:58 -0800 Subject: x86: correct the CPUID pattern for MSR_IA32_MISC_ENABLE availability Impact: re-enable CPUID unmasking on affected processors As far as I am capable of discerning from the documentation, MSR_IA32_MISC_ENABLE should be available for all family 0xf CPUs, as well as family 6 for model >= 0xd (newer Pentium M). The documentation on this isn't ideal, so we need to be on the lookout for errors, still. Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/intel.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/kernel/cpu/intel.c') diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 549f2ada55f..430e5c38a54 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -30,7 +30,7 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) { /* Unmask CPUID levels if masked: */ - if (c->x86 == 6 && c->x86_model >= 15) { + if (c->x86 > 6 || (c->x86 == 6 && c->x86_model >= 0xd)) { u64 misc_enable; rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable); -- cgit v1.2.3