1 files changed, 58 insertions, 16 deletions

diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c
index dd6e3f15017e..a11f5d4477cd 100644
--- a/arch/x86/kernel/cpu/common_64.c
+++ b/arch/x86/kernel/cpu/common_64.c
@@ -18,6 +18,7 @@
 #include <asm/mtrr.h>
 #include <asm/mce.h>
 #include <asm/pat.h>
+#include <asm/asm.h>
 #include <asm/numa.h>
 #ifdef CONFIG_X86_LOCAL_APIC
 #include <asm/mpspec.h>
@@ -215,6 +216,39 @@ static void __init early_cpu_support_print(void)
         }
 }
 
+/*
+ * The NOPL instruction is supposed to exist on all CPUs with
+ * family >= 6, unfortunately, that's not true in practice because
+ * of early VIA chips and (more importantly) broken virtualizers that
+ * are not easy to detect.  Hence, probe for it based on first
+ * principles.
+ *
+ * Note: no 64-bit chip is known to lack these, but put the code here
+ * for consistency with 32 bits, and to make it utterly trivial to
+ * diagnose the problem should it ever surface.
+ */
+static void __cpuinit detect_nopl(struct cpuinfo_x86 *c)
+{
+        const u32 nopl_signature = 0x888c53b1; /* Random number */
+        u32 has_nopl = nopl_signature;
+
+        clear_cpu_cap(c, X86_FEATURE_NOPL);
+        if (c->x86 >= 6) {
+                asm volatile("\n"
+                             "1:      .byte 0x0f,0x1f,0xc0\n" /* nopl %eax */
+                             "2:\n"
+                             "        .section .fixup,\"ax\"\n"
+                             "3:      xor %0,%0\n"
+                             "        jmp 2b\n"
+                             "        .previous\n"
+                             _ASM_EXTABLE(1b,3b)
+                             : "+a" (has_nopl));
+
+                if (has_nopl == nopl_signature)
+                        set_cpu_cap(c, X86_FEATURE_NOPL);
+        }
+}
+
 static void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c);
 
 void __init early_cpu_init(void)
@@ -313,6 +347,8 @@ static void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c)
                 c->x86_phys_bits = eax & 0xff;
         }
 
+        detect_nopl(c);
+
         if (c->x86_vendor != X86_VENDOR_UNKNOWN &&
             cpu_devs[c->x86_vendor]->c_early_init)
                 cpu_devs[c->x86_vendor]->c_early_init(c);
@@ -493,17 +529,20 @@ void pda_init(int cpu)
                 /* others are initialized in smpboot.c */
                 pda->pcurrent = &init_task;
                 pda->irqstackptr = boot_cpu_stack;
+                pda->irqstackptr += IRQSTACKSIZE - 64;
         } else {
-                pda->irqstackptr = (char *)
-                        __get_free_pages(GFP_ATOMIC, IRQSTACK_ORDER);
-                if (!pda->irqstackptr)
-                        panic("cannot allocate irqstack for cpu %d", cpu);
+                if (!pda->irqstackptr) {
+                        pda->irqstackptr = (char *)
+                                __get_free_pages(GFP_ATOMIC, IRQSTACK_ORDER);
+                        if (!pda->irqstackptr)
+                                panic("cannot allocate irqstack for cpu %d",
+                                      cpu);
+                        pda->irqstackptr += IRQSTACKSIZE - 64;
+                }
 
                 if (pda->nodenumber == 0 && cpu_to_node(cpu) != NUMA_NO_NODE)
                         pda->nodenumber = cpu_to_node(cpu);
         }
-
-        pda->irqstackptr += IRQSTACKSIZE-64;
 }
 
 char boot_exception_stacks[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ +
@@ -601,19 +640,22 @@ void __cpuinit cpu_init(void)
         /*
          * set up and load the per-CPU TSS
          */
-        for (v = 0; v < N_EXCEPTION_STACKS; v++) {
+        if (!orig_ist->ist[0]) {
                 static const unsigned int order[N_EXCEPTION_STACKS] = {
-                        [0 ... N_EXCEPTION_STACKS - 1] = EXCEPTION_STACK_ORDER,
-                        [DEBUG_STACK - 1] = DEBUG_STACK_ORDER
+                  [0 ... N_EXCEPTION_STACKS - 1] = EXCEPTION_STACK_ORDER,
+                  [DEBUG_STACK - 1] = DEBUG_STACK_ORDER
                 };
-                if (cpu) {
-                        estacks = (char *)__get_free_pages(GFP_ATOMIC, order[v]);
-                        if (!estacks)
-                                panic("Cannot allocate exception stack %ld %d\n",
-                                      v, cpu);
+                for (v = 0; v < N_EXCEPTION_STACKS; v++) {
+                        if (cpu) {
+                                estacks = (char *)__get_free_pages(GFP_ATOMIC, order[v]);
+                                if (!estacks)
+                                        panic("Cannot allocate exception "
+                                              "stack %ld %d\n", v, cpu);
+                        }
+                        estacks += PAGE_SIZE << order[v];
+                        orig_ist->ist[v] = t->x86_tss.ist[v] =
+                                        (unsigned long)estacks;
                 }
-                estacks += PAGE_SIZE << order[v];
-                orig_ist->ist[v] = t->x86_tss.ist[v] = (unsigned long)estacks;
         }
 
         t->x86_tss.io_bitmap_base = offsetof(struct tss_struct, io_bitmap);