x86: show remote CPU state upon fatal NMI or unknown MCE

Quite frequently the watchdog would hit an innocent CPU, e.g. one
trying to acquire a spin lock a remote CPU holds for extended periods
of time, or a random CPU in TSC calbration rendezvous. In such cases
the register and stack dump for that CPU doesn't really help in the
analysis of the problem.

To keep things reasonable on large systems, only log CS:RIP by default.
This can be overridden via a new command line option such that full
register/stack state would get logged.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index fed732c2d07db93135c61e9f0a0e299f1372f751..7a271c0c756cfbfb09ff690970b966bc85b97df3 100644 (file)
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -198,6 +198,14 @@ Permit Xen to use Address Space Identifiers.  This is an optimisation which
 tags the TLB entries with an ID per vcpu.  This allows for guest TLB flushes
 to be performed without the overhead of a complete TLB flush.
 
+### async-show-all
+> `= <boolean>`
+
+> Default: `false`
+
+Forces all CPUs' full state to be logged upon certain fatal asynchronous
+exceptions (watchdog NMIs and unexpected MCEs).
+
 ### ats
 > `= <boolean>`
 

diff --git a/xen/arch/x86/cpu/mcheck/mce.c b/xen/arch/x86/cpu/mcheck/mce.c
index 02445535ae96da5b529f7a1e0252960f82d209a1..edcbe4842de07598d3d24f0a21ab09584dba6e40 100644 (file)
--- a/xen/arch/x86/cpu/mcheck/mce.c
+++ b/xen/arch/x86/cpu/mcheck/mce.c
@@ -77,7 +77,7 @@ static void unexpected_machine_check(const struct cpu_user_regs *regs)
 {
     console_force_unlock();
     printk("Unexpected Machine Check Exception\n");
-    fatal_trap(regs);
+    fatal_trap(regs, 1);
 }
 
 

diff --git a/xen/arch/x86/nmi.c b/xen/arch/x86/nmi.c
index 426c24ed9b27edf1cfc408c2bf5cab92fce4dfd5..efc21b24bfe39453ab8b3e9969df1f4a8ddd8a1b 100644 (file)
--- a/xen/arch/x86/nmi.c
+++ b/xen/arch/x86/nmi.c
@@ -488,7 +488,7 @@ bool_t nmi_watchdog_tick(const struct cpu_user_regs *regs)
             console_force_unlock();
             printk("Watchdog timer detects that CPU%d is stuck!\n",
                    smp_processor_id());
-            fatal_trap(regs);
+            fatal_trap(regs, 1);
         }
     } 
     else 

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index f604b89f12475b89e2bf34b6fb7114da63ed26d2..767d0b072883fc20690d24690ed9dd2c593eb3af 100644 (file)
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -525,6 +525,25 @@ void vcpu_show_execution_state(struct vcpu *v)
     vcpu_unpause(v);
 }
 
+static cpumask_t show_state_mask;
+static bool_t opt_show_all;
+boolean_param("async-show-all", opt_show_all);
+
+static int nmi_show_execution_state(const struct cpu_user_regs *regs, int cpu)
+{
+    if ( !cpumask_test_cpu(cpu, &show_state_mask) )
+        return 0;
+
+    if ( opt_show_all )
+        show_execution_state(regs);
+    else
+        printk(XENLOG_ERR "CPU%d @ %04x:%08lx (%pS)\n", cpu, regs->cs, regs->rip,
+               guest_mode(regs) ? _p(regs->rip) : NULL);
+    cpumask_clear_cpu(cpu, &show_state_mask);
+
+    return 1;
+}
+
 static const char *trapstr(unsigned int trapnr)
 {
     static const char * const strings[] = {
@@ -544,7 +563,7 @@ static const char *trapstr(unsigned int trapnr)
  * are disabled). In such situations we can't do much that is safe. We try to
  * print out some tracing and then we just spin.
  */
-void fatal_trap(const struct cpu_user_regs *regs)
+void fatal_trap(const struct cpu_user_regs *regs, bool_t show_remote)
 {
     static DEFINE_PER_CPU(char, depth);
     unsigned int trapnr = regs->entry_vector;
@@ -570,6 +589,34 @@ void fatal_trap(const struct cpu_user_regs *regs)
             printk("Faulting linear address: %p\n", _p(cr2));
             show_page_walk(cr2);
         }
+
+        if ( show_remote )
+        {
+            unsigned int msecs, pending;
+
+            cpumask_andnot(&show_state_mask, &cpu_online_map,
+                           cpumask_of(smp_processor_id()));
+            set_nmi_callback(nmi_show_execution_state);
+            /* Ensure new callback is set before sending out the NMI. */
+            smp_wmb();
+            smp_send_nmi_allbutself();
+
+            /* Wait at most 10ms for some other CPU to respond. */
+            msecs = 10;
+            pending = cpumask_weight(&show_state_mask);
+            while ( pending && msecs-- )
+            {
+                unsigned int left;
+
+                mdelay(1);
+                left = cpumask_weight(&show_state_mask);
+                if ( left < pending )
+                {
+                    pending = left;
+                    msecs = 10;
+                }
+            }
+        }
     }
 
     panic("FATAL TRAP: vector = %d (%s)\n"
@@ -1711,7 +1758,7 @@ void do_page_fault(struct cpu_user_regs *regs)
         {
             console_start_sync();
             printk("Xen SM%cP violation\n", (pf_type == smep_fault) ? 'E' : 'A');
-            fatal_trap(regs);
+            fatal_trap(regs, 0);
         }
 
         if ( pf_type != real_fault )
@@ -1782,7 +1829,7 @@ void __init do_early_page_fault(struct cpu_user_regs *regs)
         console_start_sync();
         printk("Early fatal page fault at %04x:%p (cr2=%p, ec=%04x)\n",
                regs->cs, _p(regs->eip), _p(cr2), regs->error_code);
-        fatal_trap(regs);
+        fatal_trap(regs, 0);
     }
 }
 
@@ -3598,7 +3645,7 @@ static void pci_serr_error(const struct cpu_user_regs *regs)
     default:  /* 'fatal' */
         console_force_unlock();
         printk("\n\nNMI - PCI system error (SERR)\n");
-        fatal_trap(regs);
+        fatal_trap(regs, 0);
     }
 }
 
@@ -3613,7 +3660,7 @@ static void io_check_error(const struct cpu_user_regs *regs)
     default:  /* 'fatal' */
         console_force_unlock();
         printk("\n\nNMI - I/O ERROR\n");
-        fatal_trap(regs);
+        fatal_trap(regs, 0);
     }
 
     outb((inb(0x61) & 0x0f) | 0x08, 0x61); /* clear-and-disable IOCK */
@@ -3633,7 +3680,7 @@ static void unknown_nmi_error(const struct cpu_user_regs *regs, unsigned char re
         console_force_unlock();
         printk("Uhhuh. NMI received for unknown reason %02x.\n", reason);
         printk("Do you have a strange power saving mode enabled?\n");
-        fatal_trap(regs);
+        fatal_trap(regs, 0);
     }
 }
 

diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 2947c17a33ddb368f80e3067e81b5a1b02fb6128..ad8c64cebd20160fa55a77d9512aaafe582b8cb4 100644 (file)
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -558,6 +558,7 @@ exception_with_ints_disabled:
 
 /* No special register assumptions. */
 FATAL_exception_with_ints_disabled:
+        xorl  %esi,%esi
         movq  %rsp,%rdi
         call  fatal_trap
         BUG   /* fatal_trap() shouldn't return. */

diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index 318c92c5c886932383dfa9ed77e8d58c9c2ed07a..c69d7a4c0d4e84cc81e43e7b215cff7db565e919 100644 (file)
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -541,7 +541,7 @@ void show_registers(const struct cpu_user_regs *regs);
 void show_execution_state(const struct cpu_user_regs *regs);
 #define dump_execution_state() run_in_exception_handler(show_execution_state)
 void show_page_walk(unsigned long addr);
-void noreturn fatal_trap(const struct cpu_user_regs *regs);
+void noreturn fatal_trap(const struct cpu_user_regs *regs, bool_t show_remote);
 
 void compat_show_guest_stack(struct vcpu *v,
                              const struct cpu_user_regs *regs, int lines);