linux-kernel - Re: [PATCH v4 0/3] Allow user space to restrict and augment MSR emulation

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Message-ID: <CALMp9eS5+mV2SC-v4gusocrWtXpm-QzGoOTDGhFS9NEmuVNTDw@mail.gmail.com>
Date:   Wed, 19 Aug 2020 15:09:04 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     "Graf (AWS), Alexander" <graf@...zon.de>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>,
        "Raslan, KarimAllah" <karahmed@...zon.de>,
        Aaron Lewis <aaronlewis@...gle.com>,
        kvm list <kvm@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 0/3] Allow user space to restrict and augment MSR emulation

On Wed, Aug 19, 2020 at 2:46 PM Graf (AWS), Alexander <graf@...zon.de> wrote:

> Special MSRs like EFER also irritate me a bit. We can't really trap on them - most code paths just know they're handled in kernel. Maybe I'll add some sanity checks as well...

Why can't we intercept EFER?