[PATCH 1/2] KVM: Add KVM_EXIT_RESET to user space API header

[Anup Patel]

On Tue, Dec 10, 2013 at 7:43 AM, Alexander Graf <agraf at suse.de> wrote:
>
> On 25.11.2013, at 16:49, Anup Patel <anup.patel at linaro.org> wrote:
>
>> Currently, we don't have an exit reason for VM reset emulation
>> in user space hence this patch adds exit reason KVM_EXIT_RESET
>> for this purpose.
>>
>> This newly added KVM_EXIT_RESET will be used by KVM arm/arm64
>> in-kernel PSCI support to reset VMs.
>>
>> Signed-off-by: Anup Patel <anup.patel at linaro.org>
>> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar at linaro.org>
>> ---
>> include/uapi/linux/kvm.h |    1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 902f124..64a04cc 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -171,6 +171,7 @@ struct kvm_pit_config {
>> #define KVM_EXIT_WATCHDOG         21
>> #define KVM_EXIT_S390_TSCH        22
>> #define KVM_EXIT_EPR              23
>> +#define KVM_EXIT_RESET            24
>
> I have to admit that I'm not particularly happy with the exit name. It's not obvious from the name under which circumstances it gets triggered. Does it get triggered when a core level reset happens? Does it get triggered when a system level reset happened? When the guest requests one?

The KVM_EXIT_RESET gets triggered when system level reset is
initiated by VCPU. For arm/arm64, this is through SYSTEM_RESET
PSCI call. In KVM x86 SVM/VMX, we have KVM_EXIT_SHUTDOWN
being used for system shutdown which we have re-used for arm/arm64.

>
> I know what it does, but I find the name too generic for what it is. What you're really doing is introduce a new communication channel in parallel to MMIO / PIO / HCALL which is only used for system level reset / shutdown today.
>
> Can we treat it as such? Could you please make this a common exit number that's called something like
>
>   KVM_EXIT_SYSTEM_EVENT
>
> with a parameter that can either be TRIGGER_SHUTDOWN or TRIGGER_RESET.
>
> That way it's obvious what's going on and people don't get confused.

I don't foresee any system level operations other than SHUTDOWN
and RESET to be handled from KVM in-kernel code but I might be
wrong.

May be we can rename KVM_EXIT_SHUTDOWN and KVM_EXIT_RESET
to KVM_EXIT_SYSTEM_SHUTDOWN and KVM_EXIT_SYSTEM_RESET ??

--
Anup

>
>
> Alex
>
>
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