Re: [PATCH v10 3/5] KVM: PPC: Add support for ePAPR idle hcall in host kernel

[Scott Wood <scottwood@freescale.com>]

On 05/08/2012 05:40 AM, Alexander Graf wrote:
> 
> On 15.03.2012, at 21:52, Stuart Yoder wrote:
> 
>> From: Liu Yu-B13201 <Yu.Liu@freescale.com>
>>
>> And add a new flag definition in kvm_ppc_pvinfo to indicate
>> whether the host supports the EV_IDLE hcall.
>>
>> Signed-off-by: Liu Yu <yu.liu@freescale.com>
>> [stuart.yoder@freescale.com: cleanup,fixes for conditions allowing idle]
>> Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
>> ---
>> -v10:
>>   -ePAPR definitions now addressed in separate patch
>>   -move clearing of KVM_REQ_UNHALT after kvm_vcpu_block() call 
>>
>> arch/powerpc/include/asm/Kbuild |    1 +
>> arch/powerpc/kvm/powerpc.c      |   20 +++++++++++++++++---
>> include/linux/kvm.h             |    2 ++
>> 3 files changed, 20 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbuild
>> index 7e313f1..13d6b7b 100644
>> --- a/arch/powerpc/include/asm/Kbuild
>> +++ b/arch/powerpc/include/asm/Kbuild
>> @@ -34,5 +34,6 @@ header-y += termios.h
>> header-y += types.h
>> header-y += ucontext.h
>> header-y += unistd.h
>> +header-y += epapr_hcalls.h
>>
>> generic-y += rwsem.h
>> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
>> index d738626..7c4e5cc 100644
>> --- a/arch/powerpc/kvm/powerpc.c
>> +++ b/arch/powerpc/kvm/powerpc.c
>> @@ -38,8 +38,7 @@
>>
>> int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
>> {
>> -	return !(v->arch.shared->msr & MSR_WE) ||
>> -	       !!(v->arch.pending_exceptions) ||
>> +	return !!(v->arch.pending_exceptions) ||
> 
> Are you sure this doesn't break book3s or e500v2?

It's only used inside kvm_vcpu_block().  We only call kvm_vcpu_block()
if there's a request to go idle (MSR[WE], hcall, etc), and MSR[WE] can't
be cleared except via exception or userspace.  Exceptions are already
checked for in runnable(), and an exit to userspace would exit
kvm_vcpu_block().

-Scott