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Subject: Re: [PATCH v4 11/19] x86/cpu: Print VMX flags in /proc/cpuinfo using
 VMX_FEATURES_*
From:   Liran Alon <liran.alon@oracle.com>
In-Reply-To: <CALMp9eRAYj=dKDtnPymkUA_OOMv+9a4WdPNt4hdpFtBgzwNA9w@mail.gmail.com>
Date:   Thu, 12 Dec 2019 20:04:19 +0200
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Borislav Petkov <bp@alien8.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        =?utf-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Joerg Roedel <joro@8bytes.org>,
        Tony Luck <tony.luck@intel.com>,
        Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>,
        Len Brown <lenb@kernel.org>, Shuah Khan <shuah@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        kvm list <kvm@vger.kernel.org>, linux-edac@vger.kernel.org,
        Linux PM list <linux-pm@vger.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
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References: <20191128014016.4389-1-sean.j.christopherson@intel.com>
 <20191128014016.4389-12-sean.j.christopherson@intel.com>
 <20191212122646.GE4991@zn.tnic>
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 <4A24DE75-4E68-4EC6-B3F3-4ACB0EE82BF0@oracle.com>
 <17c6569e-d0af-539c-6d63-f4c07367d8d1@redhat.com>
 <20191212174357.GE3163@linux.intel.com>
 <52dd758d-a590-52a6-4248-22d6852b75cd@redhat.com>
 <DA429131-7A4C-4B74-A020-6CE7622ED2F8@oracle.com>
 <CALMp9eRAYj=dKDtnPymkUA_OOMv+9a4WdPNt4hdpFtBgzwNA9w@mail.gmail.com>
To:     Jim Mattson <jmattson@google.com>
Sender: linux-kernel-owner@vger.kernel.org
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> On 12 Dec 2019, at 19:57, Jim Mattson <jmattson@google.com> wrote:
>=20
> On Thu, Dec 12, 2019 at 9:53 AM Liran Alon <liran.alon@oracle.com> =
wrote:
>=20
>> Why should CPU VMX features be treated differently than standard =
CPUID deduced features?
>=20
> Do we have the right Intel people on the recipient list to answer this
> question? Presumably, Intel felt that this information should be
> available in supervisor mode only.
>=20
> Sean?

Good question. Probably because it just makes sense that Ring3 will =
never need to use
this info as all VMX instructions are privileged. i.e. Can only be =
executed in Ring0.

De-facto in KVM we have discovered this assumption to be problematic =
BTW,
as KVM created an interface to query VMX MSRs values to properly define =
the requested
vCPU model. :P (See kvm_get_msr_feature())