Disable some of the pmap_emulate_reference() DEBUG checks if option

MULTIPROCESSOR, and quote the alpha ARM to explain why; while there, make the
failure messages a bit more detailed.

diff --git a/sys/arch/alpha/alpha/pmap.c b/sys/arch/alpha/alpha/pmap.c
index 235f54f..9f9f42a 100644 (file)
--- a/sys/arch/alpha/alpha/pmap.c
+++ b/sys/arch/alpha/alpha/pmap.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: pmap.c,v 1.76 2015/05/02 20:50:08 miod Exp $ */
+/* $OpenBSD: pmap.c,v 1.77 2015/06/23 19:50:48 miod Exp $ */
 /* $NetBSD: pmap.c,v 1.154 2000/12/07 22:18:55 thorpej Exp $ */
 
 /*-
@@ -386,7 +386,7 @@ struct pmap_tlb_shootdown_job {
 struct pmap_tlb_shootdown_q {
        TAILQ_HEAD(, pmap_tlb_shootdown_job) pq_head;
        TAILQ_HEAD(, pmap_tlb_shootdown_job) pq_free;
-       int pq_pte;                     /* aggregate PTE bits */
+       int pq_pte;                     /* aggregate low PTE bits */
        int pq_tbia;                    /* pending global flush */
        struct mutex pq_mtx;            /* queue lock */
        struct pmap_tlb_shootdown_job pq_jobs[PMAP_TLB_SHOOTDOWN_MAXJOBS];
@@ -2536,17 +2536,49 @@ pmap_emulate_reference(struct proc *p, vaddr_t v, int user, int type)
 #ifdef DEBUG                           /* These checks are more expensive */
        if (!pmap_pte_v(pte))
                panic("pmap_emulate_reference: invalid pte");
+#ifndef MULTIPROCESSOR
+       /*
+        * Quoting the Alpha ARM 14.3.1.4/5/6:
+        * ``The Translation Buffer may reload and cache the old PTE value
+        *   between the time the FOR (resp. FOW, FOE) fault invalidates the
+        *   old value from the Translation Buffer and the time software
+        *   updates the PTE in memory.  Software that depends on the
+        *   processor-provided invalidate must thus be prepared to take
+        *   another FOR (resp. FOW, FOE) fault on a page after clearing the
+        *   page's PTE<FOR(resp. FOW, FOE)> bit. The second fault will
+        *   invalidate the stale PTE from the Translation Buffer, and the
+        *   processor cannot load another stale copy. Thus, in the worst case,
+        *   a multiprocessor system will take an initial FOR (resp. FOW, FOE)
+        *   fault and then an additional FOR (resp. FOW, FOE) fault on each
+        *   processor. In practice, even a single repetition is unlikely.''
+        *
+        * In practice, spurious faults on the other processors happen, at
+        * least on fast 21264 or better processors.
+        */
        if (type == ALPHA_MMCSR_FOW) {
-               if (!(*pte & (user ? PG_UWE : PG_UWE | PG_KWE)))
-                       panic("pmap_emulate_reference: write but unwritable");
-               if (!(*pte & PG_FOW))
-                       panic("pmap_emulate_reference: write but not FOW");
+               if (!(*pte & (user ? PG_UWE : PG_UWE | PG_KWE))) {
+                       panic("pmap_emulate_reference(%d,%d): "
+                           "write but unwritable pte 0x%lx",
+                           user, type, *pte);
+               }
+               if (!(*pte & PG_FOW)) {
+                       panic("pmap_emulate_reference(%d,%d): "
+                           "write but not FOW pte 0x%lx",
+                           user, type, *pte);
+               }
        } else {
-               if (!(*pte & (user ? PG_URE : PG_URE | PG_KRE)))
-                       panic("pmap_emulate_reference: !write but unreadable");
-               if (!(*pte & (PG_FOR | PG_FOE)))
-                       panic("pmap_emulate_reference: !write but not FOR|FOE");
+               if (!(*pte & (user ? PG_URE : PG_URE | PG_KRE))) {
+                       panic("pmap_emulate_reference(%d,%d): "
+                           "!write but unreadable pte 0x%lx",
+                           user, type, *pte);
+               }
+               if (!(*pte & (PG_FOR | PG_FOE))) {
+                       panic("pmap_emulate_reference(%d,%d): "
+                           "!write but not FOR|FOE pte 0x%lx",
+                           user, type, *pte);
+               }
        }
+#endif /* MULTIPROCESSOR */
        /* Other diagnostics? */
 #endif
        pa = pmap_pte_pa(pte);
@@ -2559,9 +2591,11 @@ pmap_emulate_reference(struct proc *p, vaddr_t v, int user, int type)
        pg = PHYS_TO_VM_PAGE(pa);
 
 #ifdef DIAGNOSTIC
-       if (pg == NULL)
+       if (pg == NULL) {
                panic("pmap_emulate_reference(%p, 0x%lx, %d, %d): "
-                   "pa 0x%lx not managed", p, v, user, type, pa);
+                   "pa 0x%lx (pte %p 0x%08lx) not managed",
+                   p, v, user, type, pa, pte, *pte);
+       }
 #endif
 
        /*
@@ -3515,9 +3549,8 @@ pmap_do_tlb_shootdown(struct cpu_info *ci, struct trapframe *framep)
                            pj->pj_pmap->pm_cpus & cpu_mask, cpu_id);
                        pmap_tlb_shootdown_job_put(pq, pj);
                }
-
-               pq->pq_pte = 0;
        }
+       pq->pq_pte = 0;
 
        PSJQ_UNLOCK(pq, s);
 }
@@ -3540,7 +3573,6 @@ pmap_tlb_shootdown_q_drain(struct pmap_tlb_shootdown_q *pq)
                TAILQ_REMOVE(&pq->pq_head, pj, pj_list);
                pmap_tlb_shootdown_job_put(pq, pj);
        }
-       pq->pq_pte = 0;
 }
 
 /*