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From:   Andy Lutomirski <luto@amacapital.net>
Mime-Version: 1.0 (1.0)
Subject: Re: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter
Date:   Thu, 21 Nov 2019 15:18:46 -0800
Message-Id: <B2612A75-BEC8-4FF7-9FDA-A7B55C2E0B4A@amacapital.net>
References: <3908561D78D1C84285E8C5FCA982C28F7F4DC167@ORSMSX115.amr.corp.intel.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        "Yu, Fenghua" <fenghua.yu@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        H Peter Anvin <hpa@zytor.com>,
        "Raj, Ashok" <ashok.raj@intel.com>,
        "Shankar, Ravi V" <ravi.v.shankar@intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
In-Reply-To: <3908561D78D1C84285E8C5FCA982C28F7F4DC167@ORSMSX115.amr.corp.intel.com>
To:     "Luck, Tony" <tony.luck@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> On Nov 21, 2019, at 2:29 PM, Luck, Tony <tony.luck@intel.com> wrote:
>=20
> =EF=BB=BF
>>=20
>> It would be really, really nice if we could pass this feature through to a=
 VM. Can we?
>=20
> It's hard because the MSR is core scoped rather than thread scoped.  So on=
 an HT
> enabled system a pair of logical processors gets enabled/disabled together=
.
>=20
>=20

Well that sucks.

Could we pass it through if the host has no HT?  Debugging is *so* much easi=
er in a VM.  And HT is a bit dubious these days anyway.=