[Qemu-devel] Re: [PATCH] x86: Reboot CPU on triple fault - Version 6

[Jan Kiszka <jan.kiszka@siemens.com>]

To pick this up again, as the problem is still unfixed:

Kevin Wolf wrote:
> Anthony Liguori schrieb:
>>>   Index: dyngen-exec.h
>>> ===================================================================
>>> --- dyngen-exec.h    (Revision 4215)
>>> +++ dyngen-exec.h    (Arbeitskopie)
>>> @@ -86,6 +86,7 @@
>>>  extern int fprintf(FILE *, const char *, ...);
>>>  extern int fputs(const char *, FILE *);
>>>  extern int printf(const char *, ...);
>>> +extern FILE *stderr;
>>>   
>> This is unnecessary.
> 
> Right. I'll fix this with the next version.

To accelerate this "a bit" ;), I attached a refreshed version of your
patch.

> 
>>> +
>>> +        qemu_system_reset_request();
>>>   
>> This isn't the right function to use here.  If we supported ACPI
>> shutdown, this would generate an ACPI shutdown request.  You probably
>> want to just do:
>>
>> cpu_interrupt(env, CPU_INTERRUPT_EXIT);
> 
> Your suggestion doesn't work for me either. qemu keeps hanging producing
> lots of triple faults, but there is no CPU reset. Is there even a
> function to correctly request a CPU reset only? Directly calling
> cpu_reset doesn't work here.

IMHO, qemu_system_reset_request is the right way to raise a system-wide
hard reset. I actually don't see any relation to ACPI at this lowest
level.

Jan

---
 cpu-all.h             |    1 +
 exec.c                |    2 ++
 target-i386/helper.c  |   18 ++++++++++++++++--
 target-i386/helper2.c |    5 +++++
 4 files changed, 24 insertions(+), 2 deletions(-)

Index: b/exec.c
===================================================================
--- a/exec.c
+++ b/exec.c
@@ -1302,6 +1302,8 @@ CPULogItem cpu_log_items[] = {
 #ifdef TARGET_I386
     { CPU_LOG_PCALL, "pcall",
       "show protected mode far calls/returns/exceptions" },
+    { CPU_LOG_RESET, "cpu_reset",
+      "show CPU state before CPU resets" },
 #endif
 #ifdef DEBUG_IOPORT
     { CPU_LOG_IOPORT, "ioport",
Index: b/target-i386/helper.c
===================================================================
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -1261,6 +1261,9 @@ void do_interrupt(int intno, int is_int,
     }
 }
 
+/* This should come from sysemu.h - if we could include it here... */
+void qemu_system_reset_request(void);
+
 /*
  * Check nested exceptions and change to double or triple fault if
  * needed. It should only be called, if this is not an interrupt.
@@ -1278,8 +1281,19 @@ static int check_exception(int intno, in
         fprintf(logfile, "check_exception old: 0x%x new 0x%x\n",
                 env->old_exception, intno);
 
-    if (env->old_exception == EXCP08_DBLE)
-        cpu_abort(env, "triple fault");
+    if (env->old_exception == EXCP08_DBLE) {
+        if(env->intercept & INTERCEPT_SVM_MASK) {
+            /* most probably the virtual machine should not
+               be shut down but rather caught by the VMM */
+            vmexit(SVM_EXIT_SHUTDOWN, 0);
+        }
+
+        if (loglevel & CPU_LOG_RESET)
+            fprintf(logfile, "Triple fault\n");
+
+        qemu_system_reset_request();
+        return EXCP_HLT;
+    }
 
     if ((first_contributory && second_contributory)
         || (env->old_exception == EXCP0E_PAGE &&
Index: b/target-i386/helper2.c
===================================================================
--- a/target-i386/helper2.c
+++ b/target-i386/helper2.c
@@ -363,6 +363,11 @@ void cpu_reset(CPUX86State *env)
 {
     int i;
 
+    if (loglevel & CPU_LOG_RESET) {
+        fprintf(logfile, "CPU Reset (CPU %d)\n", env->cpu_index);
+        cpu_dump_state(env, logfile, fprintf, X86_DUMP_FPU | X86_DUMP_CCOP);
+    }
+
     memset(env, 0, offsetof(CPUX86State, breakpoints));
 
     tlb_flush(env, 1);
Index: b/cpu-all.h
===================================================================
--- a/cpu-all.h
+++ b/cpu-all.h
@@ -824,6 +824,7 @@ target_phys_addr_t cpu_get_phys_page_deb
 #define CPU_LOG_PCALL      (1 << 6)
 #define CPU_LOG_IOPORT     (1 << 7)
 #define CPU_LOG_TB_CPU     (1 << 8)
+#define CPU_LOG_RESET      (1 << 9)
 
 /* define log items */
 typedef struct CPULogItem {