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.
A self-SIPI has no effect as A) a CPU can't send a SIPI from
wait-on-SIPI state and B) SIPIs are ignored in any other state.
Will post a version that additionally checks for pending INIT as well
and injects a self-ipi then.
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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