From: kfraser@localhost.localdomain <kfraser@localhost.localdomain>
Date: Mon, 31 Jul 2006 09:40:21 +0000 (+0100)
Subject: [XEN] Some suspicion that we may enter an infinite
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~15754^2~39
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https:/%22bookmarks://%22Dat/%22http:/www.example.com/cgi/%22https:/%22bookmarks:/%22Dat?a=commitdiff_plain;h=b4b462732b89593c721f7852a5323ee18fd367ea;p=xen.git

[XEN] Some suspicion that we may enter an infinite
#PF loop due to broken spurious pagefault detection.
Beef up the tracing on that code path so we can catch
some useful info if it happens.
Signed-off-by: Keir Fraser <keir@xensource.com>
---

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index aac1d70e76..44913b2f42 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -733,7 +733,10 @@ static int __spurious_page_fault(
          (l2e_get_flags(l2e) & disallowed_flags) )
         return 0;
     if ( l2e_get_flags(l2e) & _PAGE_PSE )
-        return 1;
+    {
+        l1e = l1e_empty(); /* define before use in debug tracing */
+        goto spurious;
+    }
 
     l1t = map_domain_page(mfn);
     l1e = l1t[l1_table_offset(addr)];
@@ -742,6 +745,22 @@ static int __spurious_page_fault(
     if ( !(l1e_get_flags(l1e) & required_flags) ||
          (l1e_get_flags(l1e) & disallowed_flags) )
         return 0;
+
+ spurious:
+    DPRINTK("Spurious fault in domain %u:%u at addr %lx, e/c %04x\n",
+            current->domain->domain_id, current->vcpu_id,
+            addr, regs->error_code);
+#if CONFIG_PAGING_LEVELS >= 4
+    DPRINTK(" l4e = %"PRIpte"\n", l4e_get_intpte(l4e));
+#endif
+#if CONFIG_PAGING_LEVELS >= 3
+    DPRINTK(" l3e = %"PRIpte"\n", l3e_get_intpte(l3e));
+#endif
+    DPRINTK(" l2e = %"PRIpte"\n", l2e_get_intpte(l2e));
+    DPRINTK(" l1e = %"PRIpte"\n", l1e_get_intpte(l1e));
+#ifndef NDEBUG
+    show_registers(regs);
+#endif
     return 1;
 }
 
@@ -839,11 +858,7 @@ asmlinkage int do_page_fault(struct cpu_user_regs *regs)
     if ( unlikely(!guest_mode(regs)) )
     {
         if ( spurious_page_fault(addr, regs) )
-        {
-            DPRINTK("Spurious fault in domain %u:%u at addr %lx\n",
-                    current->domain->domain_id, current->vcpu_id, addr);
             return EXCRET_not_a_fault;
-        }
 
         if ( likely((fixup = search_exception_table(regs->eip)) != 0) )
         {