linux-kernel - Re: [PATCH -tip] x86: move vmware to hypervisor

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Date:	Wed, 25 Mar 2009 09:52:51 -0700
From:	Alok Kataria <akataria@...are.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Jaswinder Singh Rajput <jaswinder@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>, x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -tip] x86: move vmware to hypervisor

On Wed, 2009-03-25 at 05:59 -0700, Ingo Molnar wrote:
> * Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:
> 
> > On Tue, 2009-03-17 at 08:50 -0700, H. Peter Anvin wrote:
> > > Jaswinder Singh Rajput wrote:
> > > >> I dont really like this one. KVM is a hypervisor too, and so is 
> > > >> Xen and lguest. VMware is one of the many types of a 
> > > >> hypervisors.
> > > > 
> > > > Can we use common hypervisor for Xen, lguest, vmware, etc.
> > > > And Xen, lguest, vmware will be the sub-options.
> > > 
> > > Obviously.  We spent a lot of time breaking up the cpu stuff into common
> > > and vendor-specific portions, we shouldn't go backwards w.r.t. hypervisors.
> > > 	
> > 
> > OK, agreed.
> > 
> > But atleast give freedom to users to disable this who are not willing to
> > use it.
> > 
> > Currently hypervisor is used only used by VMWARE, so is I prepare this
> > freedom patch:
> > 
> > From: Jaswinder Singh Rajput <jaswinderrajput@...il.com>
> > Date: Wed, 25 Mar 2009 10:40:01 +0530
> > Subject: [PATCH] x86: Introduce CONFIG_X86_VMWARE option
> > 
> > Impact: freedom to choose
> > 
> > Gives freedom to users to select or suppress CONFIG_X86_VMWARE option.
> > 
> > Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@...il.com>
> > ---
> >  arch/x86/Kconfig                  |    7 +++++++
> >  arch/x86/include/asm/hypervisor.h |    9 +++++++++
> >  arch/x86/kernel/cpu/Makefile      |    2 +-
> >  3 files changed, 17 insertions(+), 1 deletions(-)
> > 
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index f5d7d29..56e1a9c 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -554,6 +554,13 @@ config HPET_EMULATE_RTC
> >  	def_bool y
> >  	depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
> >  
> > +config X86_VMWARE
> > +	bool
> > +	default n
> > +	prompt "X86 VMware support"
> > +	---help---
> > +	 Enable X86 VMware Hypervisor support.
> > +
> >  # Mark as embedded because too many people got it wrong.
> >  # The code disables itself when not needed.
> >  config DMI
> > diff --git a/arch/x86/include/asm/hypervisor.h b/arch/x86/include/asm/hypervisor.h
> > index 369f5c5..c08ae75 100644
> > --- a/arch/x86/include/asm/hypervisor.h
> > +++ b/arch/x86/include/asm/hypervisor.h
> > @@ -20,7 +20,16 @@
> >  #ifndef ASM_X86__HYPERVISOR_H
> >  #define ASM_X86__HYPERVISOR_H
> >  
> > +#ifdef CONFIG_X86_VMWARE
> >  extern unsigned long get_hypervisor_tsc_freq(void);
> >  extern void init_hypervisor(struct cpuinfo_x86 *c);
> > +#else
> > +static inline unsigned long get_hypervisor_tsc_freq(void)
> > +{
> > +	return 0;
> > +}
> > +
> > +static inline void init_hypervisor(struct cpuinfo_x86 *c) {}
> > +#endif
> >  
> >  #endif
> > diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
> > index 3efcb2b..24372f7 100644
> > --- a/arch/x86/kernel/cpu/Makefile
> > +++ b/arch/x86/kernel/cpu/Makefile
> > @@ -9,11 +9,11 @@ endif
> >  
> >  obj-y			:= intel_cacheinfo.o addon_cpuid_features.o
> >  obj-y			+= proc.o capflags.o powerflags.o common.o
> > -obj-y			+= vmware.o hypervisor.o
> >  
> >  obj-$(CONFIG_X86_32)	+= bugs.o cmpxchg.o
> >  obj-$(CONFIG_X86_64)	+= bugs_64.o
> >  
> > +obj-$(CONFIG_X86_VMWARE)		+= vmware.o hypervisor.o
> >  obj-$(CONFIG_X86_CPU_DEBUG)		+= cpu_debug.o
> 
> vmware can be considered a CPU here, so i think making the disabling 
> also depend on PROCESSOR_SELECT.

Ingo, this code is not just to be used by VMware, the reason we did this
generically was so that a guest could run unaltered on *any* fully
virtualized hypervisor.
And give that this code is just a boot setup thing, the only thing this
patch saves over here is not running the detection code on native
systems. All the rest of the code is guarded by the
"boot_cpu_data.x86_hyper_vendor" checks anyways.  

I don't really see the point of adding one more config option just for
this. 

Thanks,
Alok


> 
> 	Ingo

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