linux-kernel - Re: [PATCH v4 16/17] kvm: x86: Add support IA32_CORE

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Message-ID: <6f6bf5b4cfe309914c6f533518ecf5e497f1bd73.camel@linux.intel.com>
Date:   Fri, 08 Mar 2019 16:03:24 +0800
From:   Xiaoyao Li <xiaoyao.li@...ux.intel.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ravi V Shankar <ravi.v.shankar@...el.com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>,
        kvm@...r.kernel.org
Subject: Re: [PATCH v4 16/17] kvm: x86: Add support IA32_CORE_CAPABILITY MSR

On Fri, 2019-03-08 at 08:54 +0100, Paolo Bonzini wrote:
> On 08/03/19 07:10, Xiaoyao Li wrote:
> > > so that non-virtualizable features are hidden and
> > > 
> > > 	if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))
> > > 		data |= CORE_CAP_SPLIT_LOCK_DETECT;
> > > 
> > > so that userspace gets "for free" the FMS list that will be added
> > > later to the kernel.
> > 
> > I think it's redundant. Because there is no case that
> > rdmsrl_safe(MSR_IA32_CORE_CAPABILITY, &data) shows no split lock detection
> > while
> > boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT).
> 
> There will be when the kernel will add a list of FMS values that have
> split lock detection but lack the core capabilities MSR.  Or at least
> that is what Fenghua said in the cover letter.
> 
> Paolo

Got it.
Thanks for your explanation.