From mboxrd@z Thu Jan  1 00:00:00 1970
From: Glauber Costa <glommer@parallels.com>
Subject: Re: [patch 08/18] x86: pvclock: generic pvclock vsyscall initialization
Date: Mon, 29 Oct 2012 18:18:20 +0400
Message-ID: <508E902C.4080402@parallels.com>
References: <20121024131340.742340256@redhat.com> <20121024131621.658249278@redhat.com>
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Cc: <kvm@vger.kernel.org>, <johnstul@us.ibm.com>, <jeremy@goop.org>,
	<zamsden@gmail.com>, <gleb@redhat.com>, <avi@redhat.com>,
	<pbonzini@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
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On 10/24/2012 05:13 PM, Marcelo Tosatti wrote:
> Index: vsyscall/arch/x86/Kconfig
> ===================================================================
> --- vsyscall.orig/arch/x86/Kconfig
> +++ vsyscall/arch/x86/Kconfig
> @@ -632,6 +632,13 @@ config PARAVIRT_SPINLOCKS
>  
>  config PARAVIRT_CLOCK
>  	bool
> +config PARAVIRT_CLOCK_VSYSCALL
> +	bool "Paravirt clock vsyscall support"
> +	depends on PARAVIRT_CLOCK && GENERIC_TIME_VSYSCALL
> +	---help---
> +	  Enable performance critical clock related system calls to
> +	  be executed in userspace, provided that the hypervisor
> +	  supports it.
>  
>  endif

Besides debugging, what is the point in having this as an
extra-selectable? Is there any case in which a virtual machine has code
for this, but may decide to run without it ?

I believe all this code in vsyscall should be wrapped in PARAVIRT_CLOCK
only.