On 2011-01-31 17:38, Gleb Natapov wrote:
> On Mon, Jan 31, 2011 at 04:40:34PM +0100, Jan Kiszka wrote:
>> On 2011-01-31 14:04, Jan Kiszka wrote:
>>> On 2011-01-31 12:36, Jan Kiszka wrote:
>>>> On 2011-01-31 11:08, Avi Kivity wrote:
>>>>> On 01/27/2011 03:10 PM, Jan Kiszka wrote:
>>>>>> Align with qemu-kvm and prepare for IO exit fix: There is no need to run
>>>>>> kvm_arch_process_irqchip_events in the inner VCPU loop. Any state change
>>>>>> this service processes will first cause an exit from kvm_cpu_exec
>>>>>> anyway. And we will have to reenter the kernel on IO exits
>>>>>> unconditionally, something that the current logic prevents.
>>>>>>
>>>>>> Signed-off-by: Jan Kiszka<jan.kiszka@xxxxxxxxxxx>
>>>>>> ---
>>>>>> kvm-all.c | 11 ++++++-----
>>>>>> 1 files changed, 6 insertions(+), 5 deletions(-)
>>>>>>
>>>>>> diff --git a/kvm-all.c b/kvm-all.c
>>>>>> index 5bfa8c0..46ecc1c 100644
>>>>>> --- a/kvm-all.c
>>>>>> +++ b/kvm-all.c
>>>>>> @@ -892,6 +892,12 @@ int kvm_cpu_exec(CPUState *env)
>>>>>>
>>>>>> DPRINTF("kvm_cpu_exec()\n");
>>>>>>
>>>>>> + if (kvm_arch_process_irqchip_events(env)) {
>>>>>> + env->exit_request = 0;
>>>>>> + env->exception_index = EXCP_HLT;
>>>>>> + return 0;
>>>>>> + }
>>>>>> +
>>>>>> do {
>>>>>> #ifndef CONFIG_IOTHREAD
>>>>>> if (env->exit_request) {
>>>>>> @@ -901,11 +907,6 @@ int kvm_cpu_exec(CPUState *env)
>>>>>> }
>>>>>
>>>>> We check for ->exit_request here
>>>>>
>>>>>> #endif
>>>>>>
>>>>>> - if (kvm_arch_process_irqchip_events(env)) {
>>>>>> - ret = 0;
>>>>>> - break;
>>>>>> - }
>>>>>> -
>>>>>
>>>>> But this checks for ->interrupt_request. What ensures that we exit when
>>>>> ->interrupt_request is set?
>>>>
>>>> Good question, need to check again. But if that turns out to be an
>>>> issue, qemu-kvm would be broken as well. I'm just aligning the code here.
>>>>
>>>
>>> The only thing we miss by moving process_irqchip_events is a self-INIT
>>> of an AP - if such thing exists in real life. In that case, the AP would
>>> cause a reset of itself, followed by a transition to HALT state.
>>
>> I checked again with the Intel spec, and a self-INIT is invalid (at
>> least when specified via shorthand). So I'm under the impression now
>> that we can safely ignore this case and leave the patch as is.
>>
>> Any different views?
>>
> IIRC if you don't use shorthand you can send INIT to self.
We didn't care so far (in qemu-kvm), do you think we should?
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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