[questions] savevm|loadvm

[questions] savevm|loadvm

[Wenhao Xu]

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Hi, all,
   I am working with switching QEMU from running in KVM mode to QEMU
emulatoin mode dynamically.
   Intuitively, if the snapshot created using savevm in kvm mode can be used
by the loadvm command in QEMU emulator mode, the switchment could makes use
of this.  I tried to do so. However, it does not work.  Any idea how to fix
it?
    Thanks for the help.

regards,
Wenhao

-- 
~_~

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[Qemu-devel] [questions] savevm|loadvm

[Wenhao Xu]

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Hi, all,
   I am working with switching QEMU from running in KVM mode to QEMU
emulatoin mode dynamically.
   Intuitively, if the snapshot created using savevm in kvm mode can be used
by the loadvm command in QEMU emulator mode, the switchment could makes use
of this.  I tried to do so. However, it does not work.  Any idea how to fix
it?
    Thanks for the help.

regards,
Wenhao

-- 
~_~

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Re: [questions] savevm|loadvm

[Juan Quintela]

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Wenhao Xu <xuwenhao2008@gmail.com> wrote:
> Hi, all,
> ¿ï½ I am working with switching QEMU from running in KVM mode to QEMU
> emulatoin mode dynamically.
> ¿ï½ Intuitively, if the snapshot created using savevm in kvm mode can be
> used by the loadvm command in QEMU emulator mode, the switchment could
> makes use of this.¿ I tried to do so. However, it does not work.¿ Any idea
> how to fix it?
> ¿ï½¿ Thanks for the help.

kvm uses a different memory layout (slots in qemu/kvm lingo), that means
that memory can't be migrated (that is a big problem).  Once that is
"fixed", you need to work on the several in-kernel chips that don't
exist in qemu (kvm-irq-chip and the like).  Once that is fixed, you can
look for what more things are broken.

Once here, why do you want to do that switch?

Later, Juan.

> regards,
> Wenhao
>
> --
> ~_~

[Qemu-devel] Re: [questions] savevm|loadvm

[Juan Quintela]

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Wenhao Xu <xuwenhao2008@gmail.com> wrote:
> Hi, all,
> ¿ï½ I am working with switching QEMU from running in KVM mode to QEMU
> emulatoin mode dynamically.
> ¿ï½ Intuitively, if the snapshot created using savevm in kvm mode can be
> used by the loadvm command in QEMU emulator mode, the switchment could
> makes use of this.¿ I tried to do so. However, it does not work.¿ Any idea
> how to fix it?
> ¿ï½¿ Thanks for the help.

kvm uses a different memory layout (slots in qemu/kvm lingo), that means
that memory can't be migrated (that is a big problem).  Once that is
"fixed", you need to work on the several in-kernel chips that don't
exist in qemu (kvm-irq-chip and the like).  Once that is fixed, you can
look for what more things are broken.

Once here, why do you want to do that switch?

Later, Juan.

> regards,
> Wenhao
>
> --
> ~_~

Re: [questions] savevm|loadvm

[Wenhao Xu]

Hi, Juan,
   I am fresh to both QEMU and KVM. But so far, I notice that QEMU
uses "KVM_SET_USER_MEMORY_REGION" to set memory region that KVM can
use and uses cpu_register_physical_memory_offset to register the same
memory to QEMU emulator, which means QEMU and KVM use the same host
virtual memory. And therefore the memory KVM modified could be
directly reflected to QEMU. I don't quite understand the different
memory layout problem between the two. So I don't know exactly what
you mean to "fix" it?

   For why switching is useful? Actually, I am a master student now
and doing a course project. What am I arguing is that QEMU could be
potentially useful to do many instrumentation analysis, but it is a
bit slow. So by combing with KVM, when the os runs to some place where
we are interested in, switch it to QEMU emulator mode and do the
analysis and then switch back.
   FYI, there is a paper doing so in Xen, "Practical taint-based
protection using demand emulation". I want to do the same "demand
emulation" for KVM.

   I am trying to patch some code.  When kvm_run returns, I tried to
synchronize the CPU state and memory dirty map, and then run into QEMU
emulator mode. However, I got an error, "qemu: fatal: invalid tss
type". I don't know exactly where is the problem.

   Thanks for helping me working this out. I am really stuck into this problem.

regards,
Wenhao

On Tue, Mar 30, 2010 at 1:22 AM, Juan Quintela <quintela@redhat.com> wrote:
> Wenhao Xu <xuwenhao2008@gmail.com> wrote:
>> Hi, all,
>> żď˝ I am working with switching QEMU from running in KVM mode to QEMU
>> emulatoin mode dynamically.
>> żď˝ Intuitively, if the snapshot created using savevm in kvm mode can be
>> used by the loadvm command in QEMU emulator mode, the switchment could
>> makes use of this.ż I tried to do so. However, it does not work.ż Any idea
>> how to fix it?
>> żď˝ż Thanks for the help.
>
> kvm uses a different memory layout (slots in qemu/kvm lingo), that means
> that memory can't be migrated (that is a big problem).  Once that is
> "fixed", you need to work on the several in-kernel chips that don't
> exist in qemu (kvm-irq-chip and the like).  Once that is fixed, you can
> look for what more things are broken.
>
> Once here, why do you want to do that switch?
>
> Later, Juan.
>
>> regards,
>> Wenhao
>>
>> --
>> ~_~
>



-- 
~_~

[Qemu-devel] Re: [questions] savevm|loadvm

[Wenhao Xu]

Hi, Juan,
   I am fresh to both QEMU and KVM. But so far, I notice that QEMU
uses "KVM_SET_USER_MEMORY_REGION" to set memory region that KVM can
use and uses cpu_register_physical_memory_offset to register the same
memory to QEMU emulator, which means QEMU and KVM use the same host
virtual memory. And therefore the memory KVM modified could be
directly reflected to QEMU. I don't quite understand the different
memory layout problem between the two. So I don't know exactly what
you mean to "fix" it?

   For why switching is useful? Actually, I am a master student now
and doing a course project. What am I arguing is that QEMU could be
potentially useful to do many instrumentation analysis, but it is a
bit slow. So by combing with KVM, when the os runs to some place where
we are interested in, switch it to QEMU emulator mode and do the
analysis and then switch back.
   FYI, there is a paper doing so in Xen, "Practical taint-based
protection using demand emulation". I want to do the same "demand
emulation" for KVM.

   I am trying to patch some code.  When kvm_run returns, I tried to
synchronize the CPU state and memory dirty map, and then run into QEMU
emulator mode. However, I got an error, "qemu: fatal: invalid tss
type". I don't know exactly where is the problem.

   Thanks for helping me working this out. I am really stuck into this problem.

regards,
Wenhao

On Tue, Mar 30, 2010 at 1:22 AM, Juan Quintela <quintela@redhat.com> wrote:
> Wenhao Xu <xuwenhao2008@gmail.com> wrote:
>> Hi, all,
>> żď˝ I am working with switching QEMU from running in KVM mode to QEMU
>> emulatoin mode dynamically.
>> żď˝ Intuitively, if the snapshot created using savevm in kvm mode can be
>> used by the loadvm command in QEMU emulator mode, the switchment could
>> makes use of this.ż I tried to do so. However, it does not work.ż Any idea
>> how to fix it?
>> żď˝ż Thanks for the help.
>
> kvm uses a different memory layout (slots in qemu/kvm lingo), that means
> that memory can't be migrated (that is a big problem).  Once that is
> "fixed", you need to work on the several in-kernel chips that don't
> exist in qemu (kvm-irq-chip and the like).  Once that is fixed, you can
> look for what more things are broken.
>
> Once here, why do you want to do that switch?
>
> Later, Juan.
>
>> regards,
>> Wenhao
>>
>> --
>> ~_~
>



-- 
~_~

Re: [questions] savevm|loadvm

[Juan Quintela]

Wenhao Xu <xuwenhao2008@gmail.com> wrote:
> Hi, Juan,
>    I am fresh to both QEMU and KVM. But so far, I notice that QEMU
> uses "KVM_SET_USER_MEMORY_REGION" to set memory region that KVM can
> use and uses cpu_register_physical_memory_offset to register the same
> memory to QEMU emulator, which means QEMU and KVM use the same host
> virtual memory. And therefore the memory KVM modified could be
> directly reflected to QEMU. I don't quite understand the different
> memory layout problem between the two. So I don't know exactly what
> you mean to "fix" it?

1st. qemu-kvm.git and qemu.git memory layouts are different, indeed with
qemu.git kvm mode. (yes it is complex and weird).

kvm vs qemu initialization is different.  Expecting to stop kvm, and run
tcg from there is not going to work.  I guess it would need a lot of
changes, but I haven't looked at it myself.

>    For why switching is useful? Actually, I am a master student now
> and doing a course project. What am I arguing is that QEMU could be
> potentially useful to do many instrumentation analysis, but it is a
> bit slow. So by combing with KVM, when the os runs to some place where
> we are interested in, switch it to QEMU emulator mode and do the
> analysis and then switch back.

idea is good, but I don't think that it is _so_ easy at this point.  tcg
and kvm basically live in a different world.  Not sure of what needs to
be done to make them back on sync.
>    FYI, there is a paper doing so in Xen, "Practical taint-based
> protection using demand emulation". I want to do the same "demand
> emulation" for KVM.
>
>    I am trying to patch some code.  When kvm_run returns, I tried to
> synchronize the CPU state and memory dirty map, and then run into QEMU
> emulator mode. However, I got an error, "qemu: fatal: invalid tss
> type". I don't know exactly where is the problem.

I guess you need to look at tcg startup, and see how it initializes
vcpus, and hack something around that when you try to run tcg at kvm_run
exit.

Have Fun :)

Later, Juan.

[Qemu-devel] Re: [questions] savevm|loadvm

[Juan Quintela]

Wenhao Xu <xuwenhao2008@gmail.com> wrote:
> Hi, Juan,
>    I am fresh to both QEMU and KVM. But so far, I notice that QEMU
> uses "KVM_SET_USER_MEMORY_REGION" to set memory region that KVM can
> use and uses cpu_register_physical_memory_offset to register the same
> memory to QEMU emulator, which means QEMU and KVM use the same host
> virtual memory. And therefore the memory KVM modified could be
> directly reflected to QEMU. I don't quite understand the different
> memory layout problem between the two. So I don't know exactly what
> you mean to "fix" it?

1st. qemu-kvm.git and qemu.git memory layouts are different, indeed with
qemu.git kvm mode. (yes it is complex and weird).

kvm vs qemu initialization is different.  Expecting to stop kvm, and run
tcg from there is not going to work.  I guess it would need a lot of
changes, but I haven't looked at it myself.

>    For why switching is useful? Actually, I am a master student now
> and doing a course project. What am I arguing is that QEMU could be
> potentially useful to do many instrumentation analysis, but it is a
> bit slow. So by combing with KVM, when the os runs to some place where
> we are interested in, switch it to QEMU emulator mode and do the
> analysis and then switch back.

idea is good, but I don't think that it is _so_ easy at this point.  tcg
and kvm basically live in a different world.  Not sure of what needs to
be done to make them back on sync.
>    FYI, there is a paper doing so in Xen, "Practical taint-based
> protection using demand emulation". I want to do the same "demand
> emulation" for KVM.
>
>    I am trying to patch some code.  When kvm_run returns, I tried to
> synchronize the CPU state and memory dirty map, and then run into QEMU
> emulator mode. However, I got an error, "qemu: fatal: invalid tss
> type". I don't know exactly where is the problem.

I guess you need to look at tcg startup, and see how it initializes
vcpus, and hack something around that when you try to run tcg at kvm_run
exit.

Have Fun :)

Later, Juan.

Re: [questions] savevm|loadvm

[Avi Kivity]

On 03/31/2010 02:31 PM, Juan Quintela wrote:
> Wenhao Xu<xuwenhao2008@gmail.com>  wrote:
>    
>> Hi, Juan,
>>     I am fresh to both QEMU and KVM. But so far, I notice that QEMU
>> uses "KVM_SET_USER_MEMORY_REGION" to set memory region that KVM can
>> use and uses cpu_register_physical_memory_offset to register the same
>> memory to QEMU emulator, which means QEMU and KVM use the same host
>> virtual memory. And therefore the memory KVM modified could be
>> directly reflected to QEMU. I don't quite understand the different
>> memory layout problem between the two. So I don't know exactly what
>> you mean to "fix" it?
>>      
> 1st. qemu-kvm.git and qemu.git memory layouts are different, indeed with
> qemu.git kvm mode. (yes it is complex and weird).
>
> kvm vs qemu initialization is different.  Expecting to stop kvm, and run
> tcg from there is not going to work.  I guess it would need a lot of
> changes, but I haven't looked at it myself.
>    

I don't think it's so far fetched.  In fact early versions of qemu-kvm 
switched between emulation and virtualization (emulate until 64-bit 
mode, also emulate mmio instructions in qemu).

Even today, all memory initialization is done via generic qemu 
mechanisms.  So long as you synchronize all state (pit, irqchip, 
registers) you should be fine.

>>     For why switching is useful? Actually, I am a master student now
>> and doing a course project. What am I arguing is that QEMU could be
>> potentially useful to do many instrumentation analysis, but it is a
>> bit slow. So by combing with KVM, when the os runs to some place where
>> we are interested in, switch it to QEMU emulator mode and do the
>> analysis and then switch back.
>>      
> idea is good, but I don't think that it is _so_ easy at this point.  tcg
> and kvm basically live in a different world.  Not sure of what needs to
> be done to make them back on sync.
>    

cpu_synchronize_state()

-- 
error compiling committee.c: too many arguments to function

[Qemu-devel] Re: [questions] savevm|loadvm

[Avi Kivity]

On 03/31/2010 02:31 PM, Juan Quintela wrote:
> Wenhao Xu<xuwenhao2008@gmail.com>  wrote:
>    
>> Hi, Juan,
>>     I am fresh to both QEMU and KVM. But so far, I notice that QEMU
>> uses "KVM_SET_USER_MEMORY_REGION" to set memory region that KVM can
>> use and uses cpu_register_physical_memory_offset to register the same
>> memory to QEMU emulator, which means QEMU and KVM use the same host
>> virtual memory. And therefore the memory KVM modified could be
>> directly reflected to QEMU. I don't quite understand the different
>> memory layout problem between the two. So I don't know exactly what
>> you mean to "fix" it?
>>      
> 1st. qemu-kvm.git and qemu.git memory layouts are different, indeed with
> qemu.git kvm mode. (yes it is complex and weird).
>
> kvm vs qemu initialization is different.  Expecting to stop kvm, and run
> tcg from there is not going to work.  I guess it would need a lot of
> changes, but I haven't looked at it myself.
>    

I don't think it's so far fetched.  In fact early versions of qemu-kvm 
switched between emulation and virtualization (emulate until 64-bit 
mode, also emulate mmio instructions in qemu).

Even today, all memory initialization is done via generic qemu 
mechanisms.  So long as you synchronize all state (pit, irqchip, 
registers) you should be fine.

>>     For why switching is useful? Actually, I am a master student now
>> and doing a course project. What am I arguing is that QEMU could be
>> potentially useful to do many instrumentation analysis, but it is a
>> bit slow. So by combing with KVM, when the os runs to some place where
>> we are interested in, switch it to QEMU emulator mode and do the
>> analysis and then switch back.
>>      
> idea is good, but I don't think that it is _so_ easy at this point.  tcg
> and kvm basically live in a different world.  Not sure of what needs to
> be done to make them back on sync.
>    

cpu_synchronize_state()

-- 
error compiling committee.c: too many arguments to function

Re: [Qemu-devel] Re: [questions] savevm|loadvm

[Paul Brook]

> Wenhao Xu <xuwenhao2008@gmail.com> wrote:
> > Hi, Juan,
> >    I am fresh to both QEMU and KVM. But so far, I notice that QEMU
> > uses "KVM_SET_USER_MEMORY_REGION" to set memory region that KVM can
> > use and uses cpu_register_physical_memory_offset to register the same
> > memory to QEMU emulator, which means QEMU and KVM use the same host
> > virtual memory. And therefore the memory KVM modified could be
> > directly reflected to QEMU. I don't quite understand the different
> > memory layout problem between the two. So I don't know exactly what
> > you mean to "fix" it?
> 
> 1st. qemu-kvm.git and qemu.git memory layouts are different, indeed with
> qemu.git kvm mode. (yes it is complex and weird).
> 
> kvm vs qemu initialization is different.  Expecting to stop kvm, and run
> tcg from there is not going to work.  I guess it would need a lot of
> changes, but I haven't looked at it myself.

FWIW I think this really *should* work, and any failure to do so is definitely 
a bug.

Paul

Re: [Qemu-devel] Re: [questions] savevm|loadvm

[Paul Brook]

> Wenhao Xu <xuwenhao2008@gmail.com> wrote:
> > Hi, Juan,
> >    I am fresh to both QEMU and KVM. But so far, I notice that QEMU
> > uses "KVM_SET_USER_MEMORY_REGION" to set memory region that KVM can
> > use and uses cpu_register_physical_memory_offset to register the same
> > memory to QEMU emulator, which means QEMU and KVM use the same host
> > virtual memory. And therefore the memory KVM modified could be
> > directly reflected to QEMU. I don't quite understand the different
> > memory layout problem between the two. So I don't know exactly what
> > you mean to "fix" it?
> 
> 1st. qemu-kvm.git and qemu.git memory layouts are different, indeed with
> qemu.git kvm mode. (yes it is complex and weird).
> 
> kvm vs qemu initialization is different.  Expecting to stop kvm, and run
> tcg from there is not going to work.  I guess it would need a lot of
> changes, but I haven't looked at it myself.

FWIW I think this really *should* work, and any failure to do so is definitely 
a bug.

Paul

Re: [questions] savevm|loadvm

[Wenhao Xu]

Does current qemu-kvm (qemu v0.12.3) use the irqchip, pit of KVM? I
cannot find any KVM_CREATE_IRQCHIP and KVM_CREATE_PIT in the qemu
code.

Concerning the interface between qemu and kvm, I have the following confusion:
1. How irqchip and pit of KVM collaborating with the irq and pit
emulation of QEMU? As far as I see, qemu-kvm still uses qemu's irq and
pit emulation, doesn't it?

2. For return from KVM to QEMU, I cannot get the meaning of two exit reasons:
   case KVM_EXIT_EXCEPTION:
       What exception will cause KVM exit?
   default:
            dprintf("kvm_arch_handle_exit\n");
            ret = kvm_arch_handle_exit(env, run);
       What exit reasons are default?

3. How could DMA interrupt the cpu when it finishes and the qemu-kvm
is still running in kvm now?

I am still working in the patch, but these confusions really prevent
me moving forward. Thanks first for you guys giving me more hints.


The following is the code so far I write:
The main idea is synchronizing the CPU state and enter into the
emulator mode when switching from kvm to emulator. I only do the
switch when the exit reason is KVM_EXIT_IRQ_WINDOW_OPEN.

However, I got the following errors:
Whenever switch from kvm to qemu, the interrupt request in qemu will
cause qemu enter into smm mode which is definitely a bug.

This is the code that tries to synchronize the CPU state when the IRQ
Window is open. And then tries to switch back to the QEMU emulator
mode.
--- qemu-0.12.3/kvm-all.c	2010-02-23 12:54:38.000000000 -0800
+++ de-0.12.3/kvm-all.c	2010-04-01 12:23:07.000000000 -0700
@@ -577,7 +577,6 @@
 {
     struct kvm_run *run = env->kvm_run;
     int ret;
-
     dprintf("kvm_cpu_exec()\n");

     do {
@@ -641,7 +640,8 @@
             dprintf("kvm_exit_unknown\n");
             break;
         case KVM_EXIT_FAIL_ENTRY:
-            dprintf("kvm_exit_fail_entry\n");
+            printf("kvm_exit_fail_entry\n");
+	    exit(1);
             break;
         case KVM_EXIT_EXCEPTION:
             dprintf("kvm_exit_exception\n");
@@ -670,7 +670,31 @@
         env->exit_request = 0;
         env->exception_index = EXCP_INTERRUPT;
     }
-
+
+    /* de, start emulation */
+    if(env->ask_for_emulation){
+      //if( (env->eflags & IF_MASK) && (run->ready_for_interrupt_injection)){
+      if(run->exit_reason == KVM_EXIT_IRQ_WINDOW_OPEN ){
+	int saved_vm_running = vm_running;
+	vm_stop(0);
+    	if (kvm_arch_get_registers(env)) {
+    	  printf("Fatal: kvm vcpu get registers failed\n");
+    	  abort();
+    	}
+    	env->kvm_state->regs_modified = 1;
+    	env->is_in_emulation = 1;
+	target_ulong pc_start =  env->segs[R_CS].base + env->eip;
+    	/* int flags = env->hflags |(env->eflags & (IOPL_MASK | TF_MASK
| RF_MASK | VM_MASK)); */
+    	/* int code32 = !((flags >> HF_CS32_SHIFT) & 1); */
+	printf("start emulation at pc: 0x%x, eip:0x%x\n", pc_start, env->eip);
+    	/* target_disas(stderr, pc_start, 10, code32); */
+    	/* env->interrupt_request = 0; */
+    	printf("tr type:%d\n", (env->tr.flags >> DESC_TYPE_SHIFT) & 0xf);
+
+	if(saved_vm_running)
+	  vm_start();
+      }
+    }
     return ret;
 }

ask_for_emulation is in the CPU_COMMON
--- qemu-0.12.3/cpu-defs.h	2010-02-23 12:54:38.000000000 -0800
+++ de-0.12.3/cpu-defs.h	2010-03-28 15:17:14.000000000 -0700
@@ -197,6 +197,8 @@
     const char *cpu_model_str;                                          \
     struct KVMState *kvm_state;                                         \
     struct kvm_run *kvm_run;                                            \
-    int kvm_fd;
+    int kvm_fd;                                                         \
+    int ask_for_emulation;     /* ask for emulation if 1 */            \
+    int is_in_emulation; /* is in emulation */

when is_in_emulation, don't enter kvm again in cpu_exec
--- qemu-0.12.3/cpu-exec.c      2010-02-23 12:54:38.000000000 -0800
+++ de-0.12.3/cpu-exec.c        2010-03-30 00:38:01.000000000 -0700
 #if defined(TARGET_I386)
-    if (!kvm_enabled()) {
-        /* put eflags in CPU temporary format */
-        CC_SRC = env->eflags & (CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);
-        DF = 1 - (2 * ((env->eflags >> 10) & 1));
-        CC_OP = CC_OP_EFLAGS;
-        env->eflags &= ~(DF_MASK | CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);
-    }
+  if (!kvm_enabled() || env->is_in_emulation) {
+    /* put eflags in CPU temporary format */
+    CC_SRC = env->eflags & (CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);
+    DF = 1 - (2 * ((env->eflags >> 10) & 1));
+    CC_OP = CC_OP_EFLAGS;
+    env->eflags &= ~(DF_MASK | CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);
+  }

-            if (kvm_enabled()) {
-                kvm_cpu_exec(env);
-                longjmp(env->jmp_env, 1);
-            }
+      if (kvm_enabled() && !env->is_in_emulation) {
+       kvm_cpu_exec(env);
+       longjmp(env->jmp_env, 1);
+      }


command "start_emulation", "stop_emulation" support in the monitor
--- qemu-0.12.3/monitor.c	2010-02-23 12:54:38.000000000 -0800
+++ de-0.12.3/monitor.c	2010-03-28 15:16:18.000000000 -0700
@@ -56,6 +56,9 @@
 #include "json-streamer.h"
 #include "json-parser.h"
 #include "osdep.h"
+/* de */

+static void do_start_emulation(Monitor *mon, const QDict *qdict,
QObject **ret_data)
+{
+  CPUState *env = mon_get_cpu();
+  env->ask_for_emulation = 1;
+  monitor_printf(mon, "Starting emulation...\n");
+}
+
+static void do_stop_emulation(Monitor *mon, const QDict *qdict,
QObject **ret_data)
+{
+  CPUState *env = mon_get_cpu();
+  env->ask_for_emulation = 0;
+  monitor_printf(mon, "Stop emulation\n");
+}
+
+static void do_is_emulation(Monitor *mon, const QDict *qdict, QObject
**ret_data)
+{
+  CPUState *env = mon_get_cpu();
+  if(env->is_in_emulation)
+    monitor_printf(mon, "Emulating now\n");
+  else
+    monitor_printf(mon, "Virtualizing now\n");
+}
+


Thanks for the help, guys. I appreciate for your time to help!

regards,
Wenhao


On Thu, Apr 1, 2010 at 1:42 AM, Avi Kivity <avi@redhat.com> wrote:
> On 03/31/2010 02:31 PM, Juan Quintela wrote:
>>
>> Wenhao Xu<xuwenhao2008@gmail.com>  wrote:
>>
>>>
>>> Hi, Juan,
>>>    I am fresh to both QEMU and KVM. But so far, I notice that QEMU
>>> uses "KVM_SET_USER_MEMORY_REGION" to set memory region that KVM can
>>> use and uses cpu_register_physical_memory_offset to register the same
>>> memory to QEMU emulator, which means QEMU and KVM use the same host
>>> virtual memory. And therefore the memory KVM modified could be
>>> directly reflected to QEMU. I don't quite understand the different
>>> memory layout problem between the two. So I don't know exactly what
>>> you mean to "fix" it?
>>>
>>
>> 1st. qemu-kvm.git and qemu.git memory layouts are different, indeed with
>> qemu.git kvm mode. (yes it is complex and weird).
>>
>> kvm vs qemu initialization is different.  Expecting to stop kvm, and run
>> tcg from there is not going to work.  I guess it would need a lot of
>> changes, but I haven't looked at it myself.
>>
>
> I don't think it's so far fetched.  In fact early versions of qemu-kvm
> switched between emulation and virtualization (emulate until 64-bit mode,
> also emulate mmio instructions in qemu).
>
> Even today, all memory initialization is done via generic qemu mechanisms.
>  So long as you synchronize all state (pit, irqchip, registers) you should
> be fine.
>
>>>    For why switching is useful? Actually, I am a master student now
>>> and doing a course project. What am I arguing is that QEMU could be
>>> potentially useful to do many instrumentation analysis, but it is a
>>> bit slow. So by combing with KVM, when the os runs to some place where
>>> we are interested in, switch it to QEMU emulator mode and do the
>>> analysis and then switch back.
>>>
>>
>> idea is good, but I don't think that it is _so_ easy at this point.  tcg
>> and kvm basically live in a different world.  Not sure of what needs to
>> be done to make them back on sync.
>>
>
> cpu_synchronize_state()
>
> --
> error compiling committee.c: too many arguments to function
>
>



-- 
~_~

[Qemu-devel] Re: [questions] savevm|loadvm

[Wenhao Xu]

Does current qemu-kvm (qemu v0.12.3) use the irqchip, pit of KVM? I
cannot find any KVM_CREATE_IRQCHIP and KVM_CREATE_PIT in the qemu
code.

Concerning the interface between qemu and kvm, I have the following confusion:
1. How irqchip and pit of KVM collaborating with the irq and pit
emulation of QEMU? As far as I see, qemu-kvm still uses qemu's irq and
pit emulation, doesn't it?

2. For return from KVM to QEMU, I cannot get the meaning of two exit reasons:
   case KVM_EXIT_EXCEPTION:
       What exception will cause KVM exit?
   default:
            dprintf("kvm_arch_handle_exit\n");
            ret = kvm_arch_handle_exit(env, run);
       What exit reasons are default?

3. How could DMA interrupt the cpu when it finishes and the qemu-kvm
is still running in kvm now?

I am still working in the patch, but these confusions really prevent
me moving forward. Thanks first for you guys giving me more hints.


The following is the code so far I write:
The main idea is synchronizing the CPU state and enter into the
emulator mode when switching from kvm to emulator. I only do the
switch when the exit reason is KVM_EXIT_IRQ_WINDOW_OPEN.

However, I got the following errors:
Whenever switch from kvm to qemu, the interrupt request in qemu will
cause qemu enter into smm mode which is definitely a bug.

This is the code that tries to synchronize the CPU state when the IRQ
Window is open. And then tries to switch back to the QEMU emulator
mode.
--- qemu-0.12.3/kvm-all.c	2010-02-23 12:54:38.000000000 -0800
+++ de-0.12.3/kvm-all.c	2010-04-01 12:23:07.000000000 -0700
@@ -577,7 +577,6 @@
 {
     struct kvm_run *run = env->kvm_run;
     int ret;
-
     dprintf("kvm_cpu_exec()\n");

     do {
@@ -641,7 +640,8 @@
             dprintf("kvm_exit_unknown\n");
             break;
         case KVM_EXIT_FAIL_ENTRY:
-            dprintf("kvm_exit_fail_entry\n");
+            printf("kvm_exit_fail_entry\n");
+	    exit(1);
             break;
         case KVM_EXIT_EXCEPTION:
             dprintf("kvm_exit_exception\n");
@@ -670,7 +670,31 @@
         env->exit_request = 0;
         env->exception_index = EXCP_INTERRUPT;
     }
-
+
+    /* de, start emulation */
+    if(env->ask_for_emulation){
+      //if( (env->eflags & IF_MASK) && (run->ready_for_interrupt_injection)){
+      if(run->exit_reason == KVM_EXIT_IRQ_WINDOW_OPEN ){
+	int saved_vm_running = vm_running;
+	vm_stop(0);
+    	if (kvm_arch_get_registers(env)) {
+    	  printf("Fatal: kvm vcpu get registers failed\n");
+    	  abort();
+    	}
+    	env->kvm_state->regs_modified = 1;
+    	env->is_in_emulation = 1;
+	target_ulong pc_start =  env->segs[R_CS].base + env->eip;
+    	/* int flags = env->hflags |(env->eflags & (IOPL_MASK | TF_MASK
| RF_MASK | VM_MASK)); */
+    	/* int code32 = !((flags >> HF_CS32_SHIFT) & 1); */
+	printf("start emulation at pc: 0x%x, eip:0x%x\n", pc_start, env->eip);
+    	/* target_disas(stderr, pc_start, 10, code32); */
+    	/* env->interrupt_request = 0; */
+    	printf("tr type:%d\n", (env->tr.flags >> DESC_TYPE_SHIFT) & 0xf);
+
+	if(saved_vm_running)
+	  vm_start();
+      }
+    }
     return ret;
 }

ask_for_emulation is in the CPU_COMMON
--- qemu-0.12.3/cpu-defs.h	2010-02-23 12:54:38.000000000 -0800
+++ de-0.12.3/cpu-defs.h	2010-03-28 15:17:14.000000000 -0700
@@ -197,6 +197,8 @@
     const char *cpu_model_str;                                          \
     struct KVMState *kvm_state;                                         \
     struct kvm_run *kvm_run;                                            \
-    int kvm_fd;
+    int kvm_fd;                                                         \
+    int ask_for_emulation;     /* ask for emulation if 1 */            \
+    int is_in_emulation; /* is in emulation */

when is_in_emulation, don't enter kvm again in cpu_exec
--- qemu-0.12.3/cpu-exec.c      2010-02-23 12:54:38.000000000 -0800
+++ de-0.12.3/cpu-exec.c        2010-03-30 00:38:01.000000000 -0700
 #if defined(TARGET_I386)
-    if (!kvm_enabled()) {
-        /* put eflags in CPU temporary format */
-        CC_SRC = env->eflags & (CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);
-        DF = 1 - (2 * ((env->eflags >> 10) & 1));
-        CC_OP = CC_OP_EFLAGS;
-        env->eflags &= ~(DF_MASK | CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);
-    }
+  if (!kvm_enabled() || env->is_in_emulation) {
+    /* put eflags in CPU temporary format */
+    CC_SRC = env->eflags & (CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);
+    DF = 1 - (2 * ((env->eflags >> 10) & 1));
+    CC_OP = CC_OP_EFLAGS;
+    env->eflags &= ~(DF_MASK | CC_O | CC_S | CC_Z | CC_A | CC_P | CC_C);
+  }

-            if (kvm_enabled()) {
-                kvm_cpu_exec(env);
-                longjmp(env->jmp_env, 1);
-            }
+      if (kvm_enabled() && !env->is_in_emulation) {
+       kvm_cpu_exec(env);
+       longjmp(env->jmp_env, 1);
+      }


command "start_emulation", "stop_emulation" support in the monitor
--- qemu-0.12.3/monitor.c	2010-02-23 12:54:38.000000000 -0800
+++ de-0.12.3/monitor.c	2010-03-28 15:16:18.000000000 -0700
@@ -56,6 +56,9 @@
 #include "json-streamer.h"
 #include "json-parser.h"
 #include "osdep.h"
+/* de */

+static void do_start_emulation(Monitor *mon, const QDict *qdict,
QObject **ret_data)
+{
+  CPUState *env = mon_get_cpu();
+  env->ask_for_emulation = 1;
+  monitor_printf(mon, "Starting emulation...\n");
+}
+
+static void do_stop_emulation(Monitor *mon, const QDict *qdict,
QObject **ret_data)
+{
+  CPUState *env = mon_get_cpu();
+  env->ask_for_emulation = 0;
+  monitor_printf(mon, "Stop emulation\n");
+}
+
+static void do_is_emulation(Monitor *mon, const QDict *qdict, QObject
**ret_data)
+{
+  CPUState *env = mon_get_cpu();
+  if(env->is_in_emulation)
+    monitor_printf(mon, "Emulating now\n");
+  else
+    monitor_printf(mon, "Virtualizing now\n");
+}
+


Thanks for the help, guys. I appreciate for your time to help!

regards,
Wenhao


On Thu, Apr 1, 2010 at 1:42 AM, Avi Kivity <avi@redhat.com> wrote:
> On 03/31/2010 02:31 PM, Juan Quintela wrote:
>>
>> Wenhao Xu<xuwenhao2008@gmail.com>  wrote:
>>
>>>
>>> Hi, Juan,
>>>    I am fresh to both QEMU and KVM. But so far, I notice that QEMU
>>> uses "KVM_SET_USER_MEMORY_REGION" to set memory region that KVM can
>>> use and uses cpu_register_physical_memory_offset to register the same
>>> memory to QEMU emulator, which means QEMU and KVM use the same host
>>> virtual memory. And therefore the memory KVM modified could be
>>> directly reflected to QEMU. I don't quite understand the different
>>> memory layout problem between the two. So I don't know exactly what
>>> you mean to "fix" it?
>>>
>>
>> 1st. qemu-kvm.git and qemu.git memory layouts are different, indeed with
>> qemu.git kvm mode. (yes it is complex and weird).
>>
>> kvm vs qemu initialization is different.  Expecting to stop kvm, and run
>> tcg from there is not going to work.  I guess it would need a lot of
>> changes, but I haven't looked at it myself.
>>
>
> I don't think it's so far fetched.  In fact early versions of qemu-kvm
> switched between emulation and virtualization (emulate until 64-bit mode,
> also emulate mmio instructions in qemu).
>
> Even today, all memory initialization is done via generic qemu mechanisms.
>  So long as you synchronize all state (pit, irqchip, registers) you should
> be fine.
>
>>>    For why switching is useful? Actually, I am a master student now
>>> and doing a course project. What am I arguing is that QEMU could be
>>> potentially useful to do many instrumentation analysis, but it is a
>>> bit slow. So by combing with KVM, when the os runs to some place where
>>> we are interested in, switch it to QEMU emulator mode and do the
>>> analysis and then switch back.
>>>
>>
>> idea is good, but I don't think that it is _so_ easy at this point.  tcg
>> and kvm basically live in a different world.  Not sure of what needs to
>> be done to make them back on sync.
>>
>
> cpu_synchronize_state()
>
> --
> error compiling committee.c: too many arguments to function
>
>



-- 
~_~

Re: [questions] savevm|loadvm

[Avi Kivity]

On 04/01/2010 10:35 PM, Wenhao Xu wrote:
> Does current qemu-kvm (qemu v0.12.3) use the irqchip, pit of KVM? I
> cannot find any KVM_CREATE_IRQCHIP and KVM_CREATE_PIT in the qemu
> code.
>
>    

Are you looking at qemu or qemu-kvm?

> Concerning the interface between qemu and kvm, I have the following confusion:
> 1. How irqchip and pit of KVM collaborating with the irq and pit
> emulation of QEMU? As far as I see, qemu-kvm still uses qemu's irq and
> pit emulation, doesn't it?
>    

No, they're completely separate.

> 2. For return from KVM to QEMU, I cannot get the meaning of two exit reasons:
>     case KVM_EXIT_EXCEPTION:
>         What exception will cause KVM exit?
>    

I think that's obsolete.

>     default:
>              dprintf("kvm_arch_handle_exit\n");
>              ret = kvm_arch_handle_exit(env, run);
>         What exit reasons are default?
>
> 3. How could DMA interrupt the cpu when it finishes and the qemu-kvm
> is still running in kvm now?
>    

Usually the device that does the dma will raise an interrupt, which qemu 
is waiting for.

> I am still working in the patch, but these confusions really prevent
> me moving forward. Thanks first for you guys giving me more hints.
>
>
> The following is the code so far I write:
> The main idea is synchronizing the CPU state and enter into the
> emulator mode when switching from kvm to emulator. I only do the
> switch when the exit reason is KVM_EXIT_IRQ_WINDOW_OPEN.
>    

That doesn't happen with qemu-kvm.

> However, I got the following errors:
> Whenever switch from kvm to qemu, the interrupt request in qemu will
> cause qemu enter into smm mode which is definitely a bug.
>    

Definitely shouldn't happen.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

[Qemu-devel] Re: [questions] savevm|loadvm

[Avi Kivity]

On 04/01/2010 10:35 PM, Wenhao Xu wrote:
> Does current qemu-kvm (qemu v0.12.3) use the irqchip, pit of KVM? I
> cannot find any KVM_CREATE_IRQCHIP and KVM_CREATE_PIT in the qemu
> code.
>
>    

Are you looking at qemu or qemu-kvm?

> Concerning the interface between qemu and kvm, I have the following confusion:
> 1. How irqchip and pit of KVM collaborating with the irq and pit
> emulation of QEMU? As far as I see, qemu-kvm still uses qemu's irq and
> pit emulation, doesn't it?
>    

No, they're completely separate.

> 2. For return from KVM to QEMU, I cannot get the meaning of two exit reasons:
>     case KVM_EXIT_EXCEPTION:
>         What exception will cause KVM exit?
>    

I think that's obsolete.

>     default:
>              dprintf("kvm_arch_handle_exit\n");
>              ret = kvm_arch_handle_exit(env, run);
>         What exit reasons are default?
>
> 3. How could DMA interrupt the cpu when it finishes and the qemu-kvm
> is still running in kvm now?
>    

Usually the device that does the dma will raise an interrupt, which qemu 
is waiting for.

> I am still working in the patch, but these confusions really prevent
> me moving forward. Thanks first for you guys giving me more hints.
>
>
> The following is the code so far I write:
> The main idea is synchronizing the CPU state and enter into the
> emulator mode when switching from kvm to emulator. I only do the
> switch when the exit reason is KVM_EXIT_IRQ_WINDOW_OPEN.
>    

That doesn't happen with qemu-kvm.

> However, I got the following errors:
> Whenever switch from kvm to qemu, the interrupt request in qemu will
> cause qemu enter into smm mode which is definitely a bug.
>    

Definitely shouldn't happen.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

[questions] savevm|loadvm

[Wenhao Xu]

Hi, all,
   I am working with switching QEMU from running in KVM mode to QEMU
emulatoin mode dynamically.
   Intuitively, if the snapshot created using savevm in kvm mode can
be used by the loadvm command in QEMU emulator mode, the switchment
could makes use of this.  I tried to do so. However, it does not work.
 Any idea how to fix it?
    Thanks for the help.

regards,
Wenhao

--
~_~