[Qemu-devel] [PATCH] Resend: x86: Reboot CPU on triple fault

[Qemu-devel] [PATCH] Resend: x86: Reboot CPU on triple fault

[lkundrak]

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This is a (slightly adjusted for 2009-01-04 SVN) resend of Jan Kiszka's
Reboot CPU on triple fault patch (see patch file for the exact reference)

It seems like a consensus was reached on how to deal with tripple faults,
but noone commited the last version (8) of the patch anyways.

Just for the record -- 386BSD relies on this behavior to reset the CPU --
it unmaps the whole address space in order to trigger a tripple fault.

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This is a slightly adjusted (for 2009-01-04 SVN) "reset on tripple fault patch"

Originally from:

Subject: [Qemu-devel] Re: [PATCH] x86: Reboot CPU on triple fault - Version 8
Message-ID: <483C340E.1030207@siemens.com>
Date: Tue, 27 May 2008 18:17:18 +0200
From: Jan Kiszka <jan.kiszka@siemens.com>

Index: exec.c
===================================================================
--- exec.c	(revision 6159)
+++ exec.c	(working copy)
@@ -1571,6 +1571,8 @@
 #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: target-i386/helper.c
===================================================================
--- target-i386/helper.c	(revision 6159)
+++ target-i386/helper.c	(working copy)
@@ -418,6 +418,11 @@
 {
     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: target-i386/op_helper.c
===================================================================
--- target-i386/op_helper.c	(revision 6159)
+++ target-i386/op_helper.c	(working copy)
@@ -1244,6 +1244,9 @@
     }
 }
 
+/* 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.
@@ -1261,9 +1264,19 @@
         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 !defined(CONFIG_USER_ONLY)
+    if (env->old_exception == EXCP08_DBLE) {
+        if (env->intercept)
+            helper_vmexit(SVM_EXIT_SHUTDOWN, 0);
 
+        if (loglevel & CPU_LOG_RESET)
+            fprintf(logfile, "Triple fault\n");
+
+        qemu_system_reset_request();
+        return EXCP_HLT;
+    }
+#endif
+
     if ((first_contributory && second_contributory)
         || (env->old_exception == EXCP0E_PAGE &&
             (second_contributory || (intno == EXCP0E_PAGE)))) {
Index: cpu-all.h
===================================================================
--- cpu-all.h	(revision 6159)
+++ cpu-all.h	(working copy)
@@ -815,6 +815,7 @@
 #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 {

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

[Jan Kiszka]

lkundrak@v3.sk wrote:
> This is a (slightly adjusted for 2009-01-04 SVN) resend of Jan Kiszka's
> Reboot CPU on triple fault patch (see patch file for the exact reference)
> 
> It seems like a consensus was reached on how to deal with tripple faults,
> but noone commited the last version (8) of the patch anyways.
> 
> Just for the record -- 386BSD relies on this behavior to reset the CPU --
> it unmaps the whole address space in order to trigger a tripple fault.
> 

Good that you picked this up! It is still on my to-do list to get this
in, but with medium prio. However, let's try to push it a bit.

> This is a slightly adjusted (for 2009-01-04 SVN) "reset on tripple fault patch"
>
> Originally from:
> 
> Subject: [Qemu-devel] Re: [PATCH] x86: Reboot CPU on triple fault - Version 8
> Message-ID: <483C340E.1030207@siemens.com>
> Date: Tue, 27 May 2008 18:17:18 +0200
> From: Jan Kiszka <jan.kiszka@siemens.com>

Note that I posted an enhanced version on 2008-09-02, also covering
reset logging for non-x86 archs. Please use that one.

...
> Index: target-i386/op_helper.c
> ===================================================================
> --- target-i386/op_helper.c	(revision 6159)
> +++ target-i386/op_helper.c	(working copy)
> @@ -1244,6 +1244,9 @@
>      }
>  }
>  
> +/* 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.
> @@ -1261,9 +1264,19 @@
>          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 !defined(CONFIG_USER_ONLY)
> +    if (env->old_exception == EXCP08_DBLE) {
> +        if (env->intercept)
> +            helper_vmexit(SVM_EXIT_SHUTDOWN, 0);
>  
> +        if (loglevel & CPU_LOG_RESET)
> +            fprintf(logfile, "Triple fault\n");
> +
> +        qemu_system_reset_request();
> +        return EXCP_HLT;
> +    }
> +#endif
> +
>      if ((first_contributory && second_contributory)
>          || (env->old_exception == EXCP0E_PAGE &&
>              (second_contributory || (intno == EXCP0E_PAGE)))) {

I meanwhile think that SVM hook should rather look like this

helper_svm_check_intercept_param(SVM_EXIT_SHUTDOWN, 0);

in order to properly check if shutdown events are actually intercepted.
Alexander, am I right?

Jan

-- 
Siemens AG, Corporate Technology, CT SE 26
Corporate Competence Center Embedded Linux

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

[Alexander Graf]

On 12.01.2009, at 13:14, Jan Kiszka <jan.kiszka@siemens.com> wrote:

> lkundrak@v3.sk wrote:
>> This is a (slightly adjusted for 2009-01-04 SVN) resend of Jan  
>> Kiszka's
>> Reboot CPU on triple fault patch (see patch file for the exact  
>> reference)
>>
>> It seems like a consensus was reached on how to deal with tripple  
>> faults,
>> but noone commited the last version (8) of the patch anyways.
>>
>> Just for the record -- 386BSD relies on this behavior to reset the  
>> CPU --
>> it unmaps the whole address space in order to trigger a tripple  
>> fault.
>>
>
> Good that you picked this up! It is still on my to-do list to get this
> in, but with medium prio. However, let's try to push it a bit.
>
>> This is a slightly adjusted (for 2009-01-04 SVN) "reset on tripple  
>> fault patch"
>>
>> Originally from:
>>
>> Subject: [Qemu-devel] Re: [PATCH] x86: Reboot CPU on triple fault -  
>> Version 8
>> Message-ID: <483C340E.1030207@siemens.com>
>> Date: Tue, 27 May 2008 18:17:18 +0200
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>
> Note that I posted an enhanced version on 2008-09-02, also covering
> reset logging for non-x86 archs. Please use that one.
>
> ...
>> Index: target-i386/op_helper.c
>> ===================================================================
>> --- target-i386/op_helper.c    (revision 6159)
>> +++ target-i386/op_helper.c    (working copy)
>> @@ -1244,6 +1244,9 @@
>>     }
>> }
>>
>> +/* 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.
>> @@ -1261,9 +1264,19 @@
>>         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 !defined(CONFIG_USER_ONLY)
>> +    if (env->old_exception == EXCP08_DBLE) {
>> +        if (env->intercept)
>> +            helper_vmexit(SVM_EXIT_SHUTDOWN, 0);
>>
>> +        if (loglevel & CPU_LOG_RESET)
>> +            fprintf(logfile, "Triple fault\n");
>> +
>> +        qemu_system_reset_request();
>> +        return EXCP_HLT;
>> +    }
>> +#endif
>> +
>>     if ((first_contributory && second_contributory)
>>         || (env->old_exception == EXCP0E_PAGE &&
>>             (second_contributory || (intno == EXCP0E_PAGE)))) {
>
> I meanwhile think that SVM hook should rather look like this
>
> helper_svm_check_intercept_param(SVM_EXIT_SHUTDOWN, 0);
>
>
> in order to properly check if shutdown events are actually  
> intercepted.
> Alexander, am I right?

Yes, sounds right. Any reason not to put the intercept in  
reset_request? (asking blindly, I don't have access to the qemu source  
right now)

Alex

>
>
> Jan
>
> -- 
> Siemens AG, Corporate Technology, CT SE 26
> Corporate Competence Center Embedded Linux

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

[Jan Kiszka]

Alexander Graf wrote:
> 
> 
> 
> 
> On 12.01.2009, at 13:14, Jan Kiszka <jan.kiszka@siemens.com> wrote:
> 
>> lkundrak@v3.sk wrote:
>>> This is a (slightly adjusted for 2009-01-04 SVN) resend of Jan Kiszka's
>>> Reboot CPU on triple fault patch (see patch file for the exact
>>> reference)
>>>
>>> It seems like a consensus was reached on how to deal with tripple
>>> faults,
>>> but noone commited the last version (8) of the patch anyways.
>>>
>>> Just for the record -- 386BSD relies on this behavior to reset the
>>> CPU --
>>> it unmaps the whole address space in order to trigger a tripple fault.
>>>
>>
>> Good that you picked this up! It is still on my to-do list to get this
>> in, but with medium prio. However, let's try to push it a bit.
>>
>>> This is a slightly adjusted (for 2009-01-04 SVN) "reset on tripple
>>> fault patch"
>>>
>>> Originally from:
>>>
>>> Subject: [Qemu-devel] Re: [PATCH] x86: Reboot CPU on triple fault -
>>> Version 8
>>> Message-ID: <483C340E.1030207@siemens.com>
>>> Date: Tue, 27 May 2008 18:17:18 +0200
>>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> Note that I posted an enhanced version on 2008-09-02, also covering
>> reset logging for non-x86 archs. Please use that one.
>>
>> ...
>>> Index: target-i386/op_helper.c
>>> ===================================================================
>>> --- target-i386/op_helper.c    (revision 6159)
>>> +++ target-i386/op_helper.c    (working copy)
>>> @@ -1244,6 +1244,9 @@
>>>     }
>>> }
>>>
>>> +/* 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.
>>> @@ -1261,9 +1264,19 @@
>>>         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 !defined(CONFIG_USER_ONLY)
>>> +    if (env->old_exception == EXCP08_DBLE) {
>>> +        if (env->intercept)
>>> +            helper_vmexit(SVM_EXIT_SHUTDOWN, 0);
>>>
>>> +        if (loglevel & CPU_LOG_RESET)
>>> +            fprintf(logfile, "Triple fault\n");
>>> +
>>> +        qemu_system_reset_request();
>>> +        return EXCP_HLT;
>>> +    }
>>> +#endif
>>> +
>>>     if ((first_contributory && second_contributory)
>>>         || (env->old_exception == EXCP0E_PAGE &&
>>>             (second_contributory || (intno == EXCP0E_PAGE)))) {
>>
>> I meanwhile think that SVM hook should rather look like this
>>
>> helper_svm_check_intercept_param(SVM_EXIT_SHUTDOWN, 0);
>>
>>
>> in order to properly check if shutdown events are actually intercepted.
>> Alexander, am I right?
> 
> Yes, sounds right. Any reason not to put the intercept in reset_request?
> (asking blindly, I don't have access to the qemu source right now)

You mean qemu_system_reset_request? That's generic code while the hook
is x86-specific.

Jan

-- 
Siemens AG, Corporate Technology, CT SE 26
Corporate Competence Center Embedded Linux

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

[Alexander Graf]

On 12.01.2009, at 17:05, Jan Kiszka <jan.kiszka@siemens.com> wrote:

> Alexander Graf wrote:
>>
>>
>>
>>
>> On 12.01.2009, at 13:14, Jan Kiszka <jan.kiszka@siemens.com> wrote:
>>
>>> lkundrak@v3.sk wrote:
>>>> This is a (slightly adjusted for 2009-01-04 SVN) resend of Jan  
>>>> Kiszka's
>>>> Reboot CPU on triple fault patch (see patch file for the exact
>>>> reference)
>>>>
>>>> It seems like a consensus was reached on how to deal with tripple
>>>> faults,
>>>> but noone commited the last version (8) of the patch anyways.
>>>>
>>>> Just for the record -- 386BSD relies on this behavior to reset the
>>>> CPU --
>>>> it unmaps the whole address space in order to trigger a tripple  
>>>> fault.
>>>>
>>>
>>> Good that you picked this up! It is still on my to-do list to get  
>>> this
>>> in, but with medium prio. However, let's try to push it a bit.
>>>
>>>> This is a slightly adjusted (for 2009-01-04 SVN) "reset on tripple
>>>> fault patch"
>>>>
>>>> Originally from:
>>>>
>>>> Subject: [Qemu-devel] Re: [PATCH] x86: Reboot CPU on triple fault -
>>>> Version 8
>>>> Message-ID: <483C340E.1030207@siemens.com>
>>>> Date: Tue, 27 May 2008 18:17:18 +0200
>>>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>>
>>> Note that I posted an enhanced version on 2008-09-02, also covering
>>> reset logging for non-x86 archs. Please use that one.
>>>
>>> ...
>>>> Index: target-i386/op_helper.c
>>>> ===================================================================
>>>> --- target-i386/op_helper.c    (revision 6159)
>>>> +++ target-i386/op_helper.c    (working copy)
>>>> @@ -1244,6 +1244,9 @@
>>>>    }
>>>> }
>>>>
>>>> +/* 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.
>>>> @@ -1261,9 +1264,19 @@
>>>>        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 !defined(CONFIG_USER_ONLY)
>>>> +    if (env->old_exception == EXCP08_DBLE) {
>>>> +        if (env->intercept)
>>>> +            helper_vmexit(SVM_EXIT_SHUTDOWN, 0);
>>>>
>>>> +        if (loglevel & CPU_LOG_RESET)
>>>> +            fprintf(logfile, "Triple fault\n");
>>>> +
>>>> +        qemu_system_reset_request();
>>>> +        return EXCP_HLT;
>>>> +    }
>>>> +#endif
>>>> +
>>>>    if ((first_contributory && second_contributory)
>>>>        || (env->old_exception == EXCP0E_PAGE &&
>>>>            (second_contributory || (intno == EXCP0E_PAGE)))) {
>>>
>>> I meanwhile think that SVM hook should rather look like this
>>>
>>> helper_svm_check_intercept_param(SVM_EXIT_SHUTDOWN, 0);
>>>
>>>
>>> in order to properly check if shutdown events are actually  
>>> intercepted.
>>> Alexander, am I right?
>>
>> Yes, sounds right. Any reason not to put the intercept in  
>> reset_request?
>> (asking blindly, I don't have access to the qemu source right now)
>
> You mean qemu_system_reset_request? That's generic code while the hook
> is x86-specific.

Sounds like the right place then. :-)

Alex

>
>
> Jan
>
> -- 
> Siemens AG, Corporate Technology, CT SE 26
> Corporate Competence Center Embedded Linux