Re: [PATCH v3 3/8] x86/split_lock: Cache the value of MSR_TEST_CTRL in percpu data

[Xiaoyao Li]

On 2/7/2020 4:23 AM, Arvind Sankar wrote:
> On Thu, Feb 06, 2020 at 03:04:07PM +0800, Xiaoyao Li wrote:
> > Cache the value of MSR_TEST_CTRL in percpu data msr_test_ctrl_cache,
> > which will be used by KVM module.
> >
> > It also avoids an expensive RDMSR instruction if SLD needs to be context
> > switched.
> >
> > Suggested-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> > Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> > ---
> >   arch/x86/include/asm/cpu.h  |  2 ++
> >   arch/x86/kernel/cpu/intel.c | 19 ++++++++++++-------
> >   2 files changed, 14 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
> > index ff567afa6ee1..2b20829db450 100644
> > --- a/arch/x86/include/asm/cpu.h
> > +++ b/arch/x86/include/asm/cpu.h
> > @@ -27,6 +27,8 @@ struct x86_cpu {
> >   };
> >   
> >   #ifdef CONFIG_HOTPLUG_CPU
> > +DECLARE_PER_CPU(u64, msr_test_ctrl_cache);
> > +
>
> Why does this depend on HOTPLUG_CPU?

Sorry, my bad,

It should be under CONFIG_CPU_SUP_INTEL