From mboxrd@z Thu Jan  1 00:00:00 1970
From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Subject: Re: [PATCH RFC V3 2/3] kvm: Note down when cpu relax intercepted
 or pause loop exited
Date: Fri, 13 Jul 2012 09:05:59 +0530
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To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, Marcelo Tosatti <mtosatti@redhat.com>, Ingo Molnar <mingo@redhat.com>, Avi Kivity <avi@redhat.com>, Rik van Riel <riel@redhat.com>, S390 <linux-s390@vger.kernel.org>, Carsten Otte <cotte@de.ibm.com>, KVM <kvm@vger.kernel.org>, chegu vinod <chegu_vinod@hp.com>, "Andrew M. Theurer" <habanero@linux.vnet.ibm.com>, LKML <linux-kernel@vger.kernel.org>, X86 <x86@kernel.org>, Gleb Natapov <gleb@redhat.com>, linux390@de.ibm.com, Srivatsa Vaddagiri <srivatsa.vaddagiri@gmail.com>, Joerg Roedel <joerg.roedel@amd.com>
List-ID: <linux-s390.vger.kernel.org>

On 07/13/2012 01:32 AM, Christian Borntraeger wrote:
> On 12/07/12 21:18, Raghavendra K T wrote:
>> +#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
> [...]
>> +	struct {
>> +		bool cpu_relax_intercepted;
>> +		bool dy_eligible;
>> +	} ple;
>> +#endif
> [...]
>>   	}
>>   	vcpu->run = page_address(page);
>> +	vcpu->ple.cpu_relax_intercepted = false;
>> +	vcpu->ple.dy_eligible = false;
>
> This struct is only defined if CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT is set, but here it
> is always accessed. Will break on !x86&&  !s390.

Yes! I forgot about archs in init function.
How about having
#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
vcpu->ple.cpu_relax_intercepted = false;
vcpu->ple.dy_eligible = false;
#endif

This would solve all the problem.

>>
>>   	r = kvm_arch_vcpu_init(vcpu);
>>   	if (r<  0)
>> @@ -1577,6 +1579,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>>   	int pass;
>>   	int i;
>>
>> +	me->ple.cpu_relax_intercepted = true;
>
> dito

currently vcpu_on_spin is used only by x86 and s390. so if some other
arch in future uses vcpu_on_spin, I believe they also have to enable
CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
what do you think?

otherwise we have to add hook everywhere
>>   	/*
>>   	 * We boost the priority of a VCPU that is runnable but not
>>   	 * currently running, because it got preempted by something
>> @@ -1602,6 +1605,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
>>   			}
>>   		}
>>   	}
>> +	me->ple.cpu_relax_intercepted = false;
>
> again.
>
> maybe define static inline access functions in kvm_host.h that are no-ops
> if CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT is not set.
>