Re: [PATCH] call kvm_cpu_synchronize_state() on target vcpu

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

Gleb Natapov wrote:
> On Wed, Sep 09, 2009 at 06:21:48PM +0200, Jan Kiszka wrote:
>> Gleb Natapov wrote:
>>> On Wed, Sep 09, 2009 at 05:57:40PM +0200, Jan Kiszka wrote:
>>>> 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
>>> It can't work with kvm since all vcpu ioctls are called on the thread
>>> that issues them.
>> Yeah, I just recalled all that on_vcpu fuzz and that upstream is still
>> horribly broken /wrt iothread+kvm. But once that is fixed, we also need
>> this fix here.
>>
> This will be done as part of transition to on_vcpu() for vcpu ioctls.
> 
>>>> works now for kvm) + you are also touching shared code here. So qemu-kvm
>>>> would benefit from keeping the diff small.
>>>>
>>> The patch doesn't touch shared code. (it is almost impossible to tell
>>> what code is shared and what's not nowadays)
>> cpu_dump_state() is definitely shared.
>>
> Ah this one line. Yes it is. But I have not good commit message for this
> one liner change for upstream :)

That's why I suggested to post the corresponding change also for
upstream. Even if it doesn't need it now, it will one day. :)

Jan

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