From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jan Kiszka <jan.kiszka@siemens.com>
Subject: Re: [PATCH] call kvm_cpu_synchronize_state() on target vcpu
Date: Wed, 09 Sep 2009 17:57:40 +0200
Message-ID: <4AA7D074.5010207@siemens.com>
References: <20090909153309.GD22885@redhat.com> <4AA7CE01.1030808@siemens.com> <20090909154919.GE22885@redhat.com>
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Cc: "avi@redhat.com" <avi@redhat.com>, kvm-devel <kvm@vger.kernel.org>
To: Gleb Natapov <gleb@redhat.com>
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Gleb Natapov wrote:
> On Wed, Sep 09, 2009 at 05:47:13PM +0200, Jan Kiszka wrote:
>> Gleb Natapov wrote:
>>> regs_modified logic doesn't work if io thread calls
>>> kvm_cpu_synchronize_state() since kvm_arch_get_registers()
>>> returns only after vcpu thread is back to kernel. Setting
>>> regs_modified to 1 at this stage causes loading of wrong vcpu
>>> state on the next vcpu_run().
>> We need this upstream too, right? Could you file the corresponding patch?
>>
> Upstream is single threaded. It shouldn't suffer from this bug.

Not if you enable iothread support (though I don't remember if that
works now for kvm) + you are also touching shared code here. So qemu-kvm
would benefit from keeping the diff small.

Jan

> 
>> Thanks,
>> Jan
>>
>>> Signed-off-by: Gleb Natapov <gleb@redhat.com>
>>> diff --git a/qemu-kvm.c b/qemu-kvm.c
>>> index 06efd41..9ab0cec 100644
>>> --- a/qemu-kvm.c
>>> +++ b/qemu-kvm.c
>>> @@ -874,14 +874,6 @@ int kvm_set_mpstate(kvm_vcpu_context_t vcpu, struct kvm_mp_state *mp_state)
>>>  }
>>>  #endif
>>>  
>>> -void kvm_cpu_synchronize_state(CPUState *env)
>>> -{
>>> -    if (!env->kvm_cpu_state.regs_modified) {
>>> -        kvm_arch_get_registers(env);
>>> -        env->kvm_cpu_state.regs_modified = 1;
>>> -    }
>>> -}
>>> -
>>>  static int handle_mmio(kvm_vcpu_context_t vcpu)
>>>  {
>>>      unsigned long addr = vcpu->run->mmio.phys_addr;
>>> @@ -1539,6 +1531,22 @@ static void on_vcpu(CPUState *env, void (*func)(void *data), void *data)
>>>          qemu_cond_wait(&qemu_work_cond);
>>>  }
>>>  
>>> +static void do_kvm_cpu_synchronize_state(void *_env)
>>> +{
>>> +    CPUState *env = _env;
>>> +    if (!env->kvm_cpu_state.regs_modified) {
>>> +        kvm_arch_save_regs(env);
>>> +        kvm_arch_load_mpstate(env);
>>> +        env->kvm_cpu_state.regs_modified = 1;
>>> +    }
>>> +}
>>> +
>>> +void kvm_cpu_synchronize_state(CPUState *env)
>>> +{
>>> +    if (!env->kvm_cpu_state.regs_modified)
>>> +        on_vcpu(env, do_kvm_cpu_synchronize_state, env);
>>> +}
>>> +
>>>  static void inject_interrupt(void *data)
>>>  {
>>>      cpu_interrupt(current_env, (long) data);
>>> diff --git a/qemu-kvm.h b/qemu-kvm.h
>>> index 2c1730b..32f74b3 100644
>>> --- a/qemu-kvm.h
>>> +++ b/qemu-kvm.h
>>> @@ -1153,12 +1153,6 @@ static inline int kvm_sync_vcpus(void)
>>>      return 0;
>>>  }
>>>  
>>> -static inline void kvm_arch_get_registers(CPUState *env)
>>> -{
>>> -    kvm_save_registers(env);
>>> -    kvm_save_mpstate(env);
>>> -}
>>> -
>>>  static inline void kvm_arch_put_registers(CPUState *env)
>>>  {
>>>      kvm_load_registers(env);
>>> diff --git a/target-i386/helper.c b/target-i386/helper.c
>>> index 4a16887..57c74a2 100644
>>> --- a/target-i386/helper.c
>>> +++ b/target-i386/helper.c
>>> @@ -746,7 +746,7 @@ void cpu_dump_state(CPUState *env, FILE *f,
>>>      static const char *seg_name[6] = { "ES", "CS", "SS", "DS", "FS", "GS" };
>>>  
>>>      if (kvm_enabled())
>>> -        kvm_arch_get_registers(env);
>>> +        kvm_cpu_synchronize_state(env);
>>>  
>>>      eflags = env->eflags;
>>>  #ifdef TARGET_X86_64
>>> --
>>> 			Gleb.
>> -- 
>> Siemens AG, Corporate Technology, CT SE 2
>> Corporate Competence Center Embedded Linux
> 
> --
> 			Gleb.

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux