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

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Message-ID: <9edabe63-b77f-d9d8-d573-7e46d944b972@redhat.com>
Date:   Fri, 8 Mar 2019 08:54:55 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Xiaoyao Li <xiaoyao.li@...ux.intel.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 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