x86: cleanup PAT cpu validation

Move the scattered checks for PAT support to a single function. Its
moved to addon_cpuid_features.c as this file is shared between 32 and
64 bit.

Remove the manipulation of the PAT feature bit and just disable PAT in
the PAT layer, based on the PAT bit provided by the CPU and the
current CPU version/model white list.

Change the boot CPU check so it works on Voyager somewhere in the
future as well :) Also panic, when a secondary has PAT disabled but
the primary one has alrady switched to PAT. We have no way to undo
that.

The white list is kept for now to ensure that we can rely on known to
work CPU types and concentrate on the software induced problems
instead of fighthing CPU erratas and subtle wreckage caused by not yet
verified CPUs. Once the PAT code has stabilized enough, we can remove
the white list and open the can of worms.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/cpu/addon_cpuid_features.c b/arch/x86/kernel/cpu/addon_cpuid_features.c
index 238468ae19931be3116e1e9de9ae0f0c1db1d2e2..c2e1ce33c7cb0e9a9bdab5d16c204c9a83447f7a 100644 (file)
--- a/arch/x86/kernel/cpu/addon_cpuid_features.c
+++ b/arch/x86/kernel/cpu/addon_cpuid_features.c
@@ -6,6 +6,7 @@
 
 #include <linux/cpu.h>
 
+#include <asm/pat.h>
 #include <asm/processor.h>
 
 struct cpuid_bit {
@@ -48,3 +49,23 @@ void __cpuinit init_scattered_cpuid_features(struct cpuinfo_x86 *c)
                        set_cpu_cap(c, cb->feature);
        }
 }
+
+#ifdef CONFIG_X86_PAT
+void __cpuinit validate_pat_support(struct cpuinfo_x86 *c)
+{
+       switch (c->x86_vendor) {
+       case X86_VENDOR_AMD:
+               if (c->x86 >= 0xf && c->x86 <= 0x11)
+                       return;
+               break;
+       case X86_VENDOR_INTEL:
+               if (c->x86 == 0xF || (c->x86 == 6 && c->x86_model >= 15))
+                       return;
+               break;
+       }
+
+       pat_disable(cpu_has_pat ?
+                   "PAT disabled. Not yet verified on this CPU type." :
+                   "PAT not supported by CPU.");
+}
+#endif

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 35b4f6a9c8effca5b2a609aedb669417d26b5f66..d0463a9462477716bd065b5c822cd34e96812282 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -12,6 +12,7 @@
 #include <asm/mmu_context.h>
 #include <asm/mtrr.h>
 #include <asm/mce.h>
+#include <asm/pat.h>
 #ifdef CONFIG_X86_LOCAL_APIC
 #include <asm/mpspec.h>
 #include <asm/apic.h>
@@ -308,19 +309,6 @@ static void __cpuinit early_get_cap(struct cpuinfo_x86 *c)
 
        }
 
-       clear_cpu_cap(c, X86_FEATURE_PAT);
-
-       switch (c->x86_vendor) {
-       case X86_VENDOR_AMD:
-               if (c->x86 >= 0xf && c->x86 <= 0x11)
-                       set_cpu_cap(c, X86_FEATURE_PAT);
-               break;
-       case X86_VENDOR_INTEL:
-               if (c->x86 == 0xF || (c->x86 == 6 && c->x86_model >= 15))
-                       set_cpu_cap(c, X86_FEATURE_PAT);
-               break;
-       }
-
 }
 
 /*
@@ -409,18 +397,6 @@ static void __cpuinit generic_identify(struct cpuinfo_x86 *c)
                init_scattered_cpuid_features(c);
        }
 
-       clear_cpu_cap(c, X86_FEATURE_PAT);
-
-       switch (c->x86_vendor) {
-       case X86_VENDOR_AMD:
-               if (c->x86 >= 0xf && c->x86 <= 0x11)
-                       set_cpu_cap(c, X86_FEATURE_PAT);
-               break;
-       case X86_VENDOR_INTEL:
-               if (c->x86 == 0xF || (c->x86 == 6 && c->x86_model >= 15))
-                       set_cpu_cap(c, X86_FEATURE_PAT);
-               break;
-       }
 }
 
 static void __cpuinit squash_the_stupid_serial_number(struct cpuinfo_x86 *c)
@@ -651,6 +627,7 @@ void __init early_cpu_init(void)
                cpu_devs[cvdev->vendor] = cvdev->cpu_dev;
 
        early_cpu_detect();
+       validate_pat_support(&boot_cpu_data);
 }
 
 /* Make sure %fs is initialized properly in idle threads */

diff --git a/arch/x86/kernel/setup_64.c b/arch/x86/kernel/setup_64.c
index 22c14e21c97c435a8d172d8f23159738bf0dbe2f..80d80fab70068f44bbaa0ceb599bf85974078438 100644 (file)
--- a/arch/x86/kernel/setup_64.c
+++ b/arch/x86/kernel/setup_64.c
@@ -70,6 +70,7 @@
 #include <asm/ds.h>
 #include <asm/topology.h>
 #include <asm/trampoline.h>
+#include <asm/pat.h>
 
 #include <mach_apic.h>
 #ifdef CONFIG_PARAVIRT
@@ -1063,25 +1064,19 @@ static void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c)
        if (c->extended_cpuid_level >= 0x80000007)
                c->x86_power = cpuid_edx(0x80000007);
 
-
-       clear_cpu_cap(c, X86_FEATURE_PAT);
-
        switch (c->x86_vendor) {
        case X86_VENDOR_AMD:
                early_init_amd(c);
-               if (c->x86 >= 0xf && c->x86 <= 0x11)
-                       set_cpu_cap(c, X86_FEATURE_PAT);
                break;
        case X86_VENDOR_INTEL:
                early_init_intel(c);
-               if (c->x86 == 0xF || (c->x86 == 6 && c->x86_model >= 15))
-                       set_cpu_cap(c, X86_FEATURE_PAT);
                break;
        case X86_VENDOR_CENTAUR:
                early_init_centaur(c);
                break;
        }
 
+       validate_pat_support(c);
 }
 
 /*

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 277446cd30b6de81a4634061949385cb6eaede69..60adbe22efa0d66e3885cbb39ed5f65c521a8fde 100644 (file)
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -25,31 +25,24 @@
 #include <asm/mtrr.h>
 #include <asm/io.h>
 
-int pat_wc_enabled = 1;
+#ifdef CONFIG_X86_PAT
+int __read_mostly pat_wc_enabled = 1;
 
-static u64 __read_mostly boot_pat_state;
-
-static int nopat(char *str)
+void __init pat_disable(char *reason)
 {
        pat_wc_enabled = 0;
-       printk(KERN_INFO "x86: PAT support disabled.\n");
-
-       return 0;
+       printk(KERN_INFO "%s\n", reason);
 }
-early_param("nopat", nopat);
 
-static int pat_known_cpu(void)
+static int nopat(char *str)
 {
-       if (!pat_wc_enabled)
-               return 0;
-
-       if (cpu_has_pat)
-               return 1;
-
-       pat_wc_enabled = 0;
-       printk(KERN_INFO "CPU and/or kernel does not support PAT.\n");
+       pat_disable("PAT support disabled.");
        return 0;
 }
+early_param("nopat", nopat);
+#endif
+
+static u64 __read_mostly boot_pat_state;
 
 enum {
        PAT_UC = 0,             /* uncached */
@@ -66,17 +59,19 @@ void pat_init(void)
 {
        u64 pat;
 
-#ifndef CONFIG_X86_PAT
-       nopat(NULL);
-#endif
-
-       /* Boot CPU enables PAT based on CPU feature */
-       if (!smp_processor_id() && !pat_known_cpu())
+       if (!pat_wc_enabled)
                return;
 
-       /* APs enable PAT iff boot CPU has enabled it before */
-       if (smp_processor_id() && !pat_wc_enabled)
-               return;
+       /* Paranoia check. */
+       if (!cpu_has_pat) {
+               printk(KERN_ERR "PAT enabled, but CPU feature cleared\n");
+               /*
+                * Panic if this happens on the secondary CPU, and we
+                * switched to PAT on the boot CPU. We have no way to
+                * undo PAT.
+               */
+               BUG_ON(boot_pat_state);
+       }
 
        /* Set PWT to Write-Combining. All other bits stay the same */
        /*
@@ -95,9 +90,8 @@ void pat_init(void)
              PAT(4,WB) | PAT(5,WC) | PAT(6,UC_MINUS) | PAT(7,UC);
 
        /* Boot CPU check */
-       if (!smp_processor_id()) {
+       if (!boot_pat_state)
                rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
-       }
 
        wrmsrl(MSR_IA32_CR_PAT, pat);
        printk(KERN_INFO "x86 PAT enabled: cpu %d, old 0x%Lx, new 0x%Lx\n",

diff --git a/include/asm-x86/pat.h b/include/asm-x86/pat.h
index 8b822b5a17861215eacfa2d7253ea99c84f310b7..88f60cc6a22737f8e45b20e36a67b27410bb5326 100644 (file)
--- a/include/asm-x86/pat.h
+++ b/include/asm-x86/pat.h
@@ -4,7 +4,13 @@
 
 #include <linux/types.h>
 
+#ifdef CONFIG_X86_PAT
 extern int pat_wc_enabled;
+extern void validate_pat_support(struct cpuinfo_x86 *c);
+#else
+static const int pat_wc_enabled = 0;
+static inline void validate_pat_support(struct cpuinfo_x86 *c) { }
+#endif
 
 extern void pat_init(void);
 
@@ -12,5 +18,7 @@ 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