linux-kernel - Re: [PATCH RFC V3 2/3] kvm: Note down when cpu relax intercepted or pause loop exited

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Date:	Thu, 12 Jul 2012 22:02:39 +0200
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Avi Kivity <avi@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	S390 <linux-s390@...r.kernel.org>,
	Carsten Otte <cotte@...ibm.com>, KVM <kvm@...r.kernel.org>,
	chegu vinod <chegu_vinod@...com>,
	"Andrew M. Theurer" <habanero@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>, X86 <x86@...nel.org>,
	Gleb Natapov <gleb@...hat.com>, linux390@...ibm.com,
	Srivatsa Vaddagiri <srivatsa.vaddagiri@...il.com>,
	Joerg Roedel <joerg.roedel@....com>
Subject: Re: [PATCH RFC V3 2/3] kvm: Note down when cpu relax intercepted
 or pause loop exited

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.
> 
>  	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
>  	/*
>  	 * 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.

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