From 75a048119e76540d73132cfc8e0fa0c0a8bb6c83 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Thu, 22 Jan 2009 16:17:05 -0800 Subject: [PATCH] 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/include/asm/pat.h | 4 --- arch/x86/kernel/cpu/addon_cpuid_features.c | 34 ---------------------- arch/x86/kernel/cpu/common.c | 2 -- arch/x86/kernel/cpu/intel.c | 12 ++++++++ arch/x86/mm/pat.c | 31 +++++++++++++------- 5 files changed, 32 insertions(+), 51 deletions(-) diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h index b8493b3b9890..9709fdff6615 100644 --- a/arch/x86/include/asm/pat.h +++ b/arch/x86/include/asm/pat.h @@ -5,10 +5,8 @@ #ifdef CONFIG_X86_PAT extern int pat_enabled; -extern void validate_pat_support(struct cpuinfo_x86 *c); #else static const int pat_enabled; -static inline void validate_pat_support(struct cpuinfo_x86 *c) { } #endif extern void pat_init(void); @@ -17,6 +15,4 @@ extern int reserve_memtype(u64 start, u64 end, unsigned long req_type, unsigned long *ret_type); extern int free_memtype(u64 start, u64 end); -extern void pat_disable(char *reason); - #endif /* _ASM_X86_PAT_H */ diff --git a/arch/x86/kernel/cpu/addon_cpuid_features.c b/arch/x86/kernel/cpu/addon_cpuid_features.c index 2cf23634b6d9..4e581fdc0a5a 100644 --- a/arch/x86/kernel/cpu/addon_cpuid_features.c +++ b/arch/x86/kernel/cpu/addon_cpuid_features.c @@ -143,37 +143,3 @@ void __cpuinit detect_extended_topology(struct cpuinfo_x86 *c) 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 83492b1f93b1..0f8656361e04 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -570,8 +570,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) 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 8ea6929e974c..20ce03acf04b 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 diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index 8b08fb955274..430cb44dd3f4 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -30,7 +30,7 @@ #ifdef CONFIG_X86_PAT int __read_mostly pat_enabled = 1; -void __cpuinit pat_disable(char *reason) +void __cpuinit pat_disable(const char *reason) { pat_enabled = 0; printk(KERN_INFO "%s\n", reason); @@ -42,6 +42,11 @@ static int __init nopat(char *str) return 0; } early_param("nopat", nopat); +#else +static inline void pat_disable(const char *reason) +{ + (void)reason; +} #endif @@ -78,16 +83,20 @@ void pat_init(void) if (!pat_enabled) return; - /* Paranoia check. */ - if (!cpu_has_pat && boot_pat_state) { - /* - * If this happens we are on a secondary CPU, but - * switched to PAT on the boot CPU. We have no way to - * undo PAT. - */ - printk(KERN_ERR "PAT enabled, " - "but not supported by secondary CPU\n"); - BUG(); + if (!cpu_has_pat) { + if (!boot_pat_state) { + pat_disable("PAT not supported by CPU."); + return; + } else { + /* + * If this happens we are on a secondary CPU, but + * switched to PAT on the boot CPU. We have no way to + * undo PAT. + */ + printk(KERN_ERR "PAT enabled, " + "but not supported by secondary CPU\n"); + BUG(); + } } /* Set PWT to Write-Combining. All other bits stay the same */