On 02/17/2017 04:12 PM, Radim Krčmář wrote:
> 2017-02-17 14:10+0100, Christian Borntraeger:
>> needed by KVM common code.
>>
>> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
>> ---
>> arch/s390/kernel/smp.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
>> index 4c9ebb3..a4d7124 100644
>> --- a/arch/s390/kernel/smp.c
>> +++ b/arch/s390/kernel/smp.c
>> @@ -513,6 +513,7 @@ void smp_send_reschedule(int cpu)
>> {
>> pcpu_ec_call(pcpu_devices + cpu, ec_schedule);
>> }
>> +EXPORT_SYMBOL_GPL(smp_send_reschedule);
>
> s390 doesn't want to use smp_send_reschedule() so I think the patch at
> the bottom is going in a better direction.
>
> Btw. I think that we shouldn't be using smp_send_reschedule() for
> forcing VCPUs out of guest mode anyway -- the task we want to run is
> already scheduled and we don't want the schduler to do anything.
>
> We could use smp_call_function() with an empty function instead, but
> that also has high overhead ... allocating a new IPI seems best.
>
> But optimizing the current code is premature. :)
>
> ---8<---
> s390 has a different mechanism from bringing the VCPU out of guest mode.
> Make the kick arch-specific.
Looks good. The kick does not have to be synchronous and its ok if we
reenter the guest as long as we execute the request in a timely manner,
correct?
e.g.
- kick vcpu
- vcpu enters SIE
- vcpu exits SIE immediately
- vcpu handles request
- vcpu enters SIE
would be perfectly fine?
In that case the s390 implementation could be pretty simple.
>
> Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> ---
> arch/arm/kvm/arm.c | 5 +++++
> arch/mips/kvm/mips.c | 5 +++++
> arch/powerpc/kvm/powerpc.c | 5 +++++
> arch/s390/kvm/kvm-s390.c | 6 ++++++
> arch/x86/kvm/x86.c | 5 +++++
> include/linux/kvm_host.h | 1 +
> virt/kvm/kvm_main.c | 2 +-
> 7 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 21c493a9e5c9..a52b0399fa43 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -97,6 +97,11 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
> return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
> }
>
> +void kvm_arch_cpu_kick(int cpu)
> +{
> + smp_send_reschedule(cpu);
> +}
> +
> int kvm_arch_hardware_setup(void)
> {
> return 0;
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index 31ee5ee0010b..8ed510d7f8c5 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -78,6 +78,11 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
> return 1;
> }
>
> +void kvm_arch_cpu_kick(int cpu)
> +{
> + smp_send_reschedule(cpu);
> +}
> +
> int kvm_arch_hardware_enable(void)
> {
> return 0;
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index b094d9c1e1ef..b31149e63817 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -60,6 +60,11 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
> return 1;
> }
>
> +void kvm_arch_cpu_kick(int cpu)
> +{
> + smp_send_reschedule(cpu);
> +}
> +
> /*
> * Common checks before entering the guest world. Call with interrupts
> * disabled.
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 8e36734fa5b6..f67ec9796f5e 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2131,6 +2131,12 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> +void kvm_arch_cpu_kick(int cpu)
> +{
> + /* TODO: implement kicking with SIE */
> + BUG();
> +}
> +
> static int kvm_arch_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu,
> struct kvm_one_reg *reg)
> {
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 19c853f87dd4..d6f40f20c0b5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8405,6 +8405,11 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
> return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
> }
>
> +void kvm_arch_cpu_kick(int cpu)
> +{
> + smp_send_reschedule(cpu);
> +}
> +
> int kvm_arch_interrupt_allowed(struct kvm_vcpu *vcpu)
> {
> return kvm_x86_ops->interrupt_allowed(vcpu);
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 5438548fec10..9872bd7713f1 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -766,6 +766,7 @@ void kvm_arch_hardware_unsetup(void);
> void kvm_arch_check_processor_compat(void *rtn);
> int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
> int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
> +void kvm_arch_cpu_kick(int cpu);
>
> void *kvm_kvzalloc(unsigned long size);
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 8d2ef0661ea8..4f4d250e1f53 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2240,7 +2240,7 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
> me = get_cpu();
> if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))
> if (kvm_arch_vcpu_should_kick(vcpu))
> - smp_send_reschedule(cpu);
> + kvm_arch_cpu_kick(cpu);
> put_cpu();
> }
> EXPORT_SYMBOL_GPL(kvm_vcpu_kick);
>
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