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Diffstat (limited to 'arch/x86/mm/pat.c')
-rw-r--r--arch/x86/mm/pat.c50
1 files changed, 22 insertions, 28 deletions
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 277446cd30b6..60adbe22efa0 100644
--- 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",