Some simple NMI handling and logging.

94264a7d · Silas Boyd-Wickizer · 2ee21cd7 · 94264a7d · 94264a7d · 94264a7d
--- a/kernel.h
+++ b/kernel.h
@@ -20,6 +20,7 @@ static inline void *p2v(uptr a) { return (void *) a + KBASE; }
 #define fetchadd(ptr, val)     __sync_fetch_and_add(ptr, val)
 #define __offsetof             offsetof

+struct trapframe;
 struct spinlock;
 struct condvar;
 struct wqframe;
@@ -211,7 +212,7 @@ extern int profenable;
 void            profreset(void);
 void            profdump(void);
 void            profstart(void);
-int             profintr(void);
+int             profintr(struct trapframe*);

 // rcu.c
 void            rcuinit(void);

--- a/prof.c
+++ b/prof.c
@@ -9,6 +9,18 @@
 #include "bits.h"
 #include "amd64.h"

+static const u64 debug_sel = 
+  0UL << 32 |
+  1 << 24 | 
+  1 << 22 | 
+  1 << 20 |
+  1 << 17 | 
+  1 << 16 | 
+  0x00 << 8 | 
+  0x76;
+
+static const u64 debug_cnt = 100000;
+
 extern profctr_t sprof[];
 extern profctr_t eprof[];
 int profenable;
@@ -19,6 +31,21 @@ struct pmu {
 };
 struct pmu pmu;

+struct pmuevent {
+  u64 rip;
+};
+
+struct pmulog {
+  u64 head;
+  u64 tail;
+  u64 size;
+  u64 try;
+  struct pmuevent *event;
+  __padout__;
+} __mpalign__;
+
+struct pmulog pmulog[NCPU] __mpalign__;
+
 //
 // AMD stuff
 //
@@ -80,34 +107,55 @@ profdump(void)
    if (cnt)
      cprintf("%s %lu\n", p->name, tot/cnt);
  }
+
+  cprintf("pmu\n");
+  for (int c = 0; c < NCPU; c++) {
+    struct pmulog *l = &pmulog[c];    
+    for (u64 i = l->tail; i < l->head; i++)
+      cprintf(" %lx\n", l->event[i % l->size].rip);
+  }
 }

 void
 profstart(void)
 {
-  u64 ctr = 0;
-  u64 sel = 0;
-  u64 val = -100000;
-
-  sel = 0UL << 32 |
-    1 << 24 | 
-    1 << 22 | 
-    1 << 20 |
-    1 << 17 | 
-    1 << 16 | 
-    0x00 << 8 | 
-    0x76;
-
  pushcli();
-  pmu.config(ctr, sel, val);
+  pmu.config(0, debug_sel, -debug_cnt);
  popcli();
 }

+static int
+proflog(struct trapframe *tf)
+{
+  struct pmulog *l;
+  l = &pmulog[cpunum()];
+  l->try++;
+
+  if ((l->head - l->tail) == l->size)
+    return 0;
+
+  l->event[l->head % l->size].rip = tf->rip;
+  l->head++;
+  return 1;
+}
+
 int
-profintr(void)
+profintr(struct trapframe *tf)
 {
+  // Acquire locks that are we only acquire during NMI.
+  // NMIs are disabled until the next iret.
+
+  // Linux unmasks LAPIC.PC after every interrupt (perf_event.c)
  lapicpc(0);
  // Only level-triggered interrupts require an lapiceoi.
+
+  u64 cnt = rdpmc(0);
+  if (cnt & (1ULL << (pmu.cntval_bits - 1)))
+    return 0;
+
+  if (proflog(tf))
+    pmu.config(0, debug_sel, -debug_cnt);
+
  return 1;
 }

@@ -132,4 +180,10 @@ initprof(void)
  // enable RDPMC at CPL > 0
  u64 cr4 = rcr4();
  lcr4(cr4 | CR4_PCE);
+  
+  void *p = kalloc();
+  if (p == NULL)
+    panic("initprof: kalloc");
+  pmulog[cpunum()].event = p;
+  pmulog[cpunum()].size = PGSIZE / sizeof(struct pmuevent);
 }
--- a/trap.c
+++ b/trap.c
@@ -48,7 +48,7 @@ trap(struct trapframe *tf)
  if (tf->trapno == T_NMI) {
    // The only locks that we can acquire during NMI are ones
    // we acquire only during NMI.
-    if (profintr())
+    if (profintr(tf))
      return;
    panic("NMI");
  }