linux-kernel - Re: [PATCH 4/4] x86,module: Detect CRn and DRn manipulation

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Date:   Wed, 8 Apr 2020 10:37:38 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Andrew Cooper <andrew.cooper3@...rix.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, hch@...radead.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        mingo <mingo@...hat.com>, bp <bp@...en8.de>, hpa@...or.com,
        x86 <x86@...nel.org>, "Kenneth R. Crudup" <kenny@...ix.com>,
        Jessica Yu <jeyu@...nel.org>,
        Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Tony Luck <tony.luck@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        jannh@...gle.com, keescook@...omium.org, David.Laight@...lab.com,
        Doug Covelli <dcovelli@...are.com>, mhiramat@...nel.org
Subject: Re: [PATCH 4/4] x86,module: Detect CRn and DRn manipulation

On Wed, Apr 08, 2020 at 02:22:45AM +0200, Paolo Bonzini wrote:
> On 08/04/20 01:15, Andrew Cooper wrote:
> >> Anyhow, I do not think it is the only use-case which is not covered by your
> >> patches (even considering CRs/DRs alone). For example, there is no kernel
> >> function to turn on CR4.VMXE, which is required to run hypervisors on x86.
> > How about taking this opportunity to see if there is a way to improve on
> > the status quo for co-existing hypervisor modules?
> 
> Almost serious question: why?  I can understand VMware, but why can't at
> least VirtualBox use KVM on Linux?  I am not sure if they are still
> running device emulation in ring zero, but if so do you really want to
> do that these days?

Having had the 'joy' of looking at the virtual-puke^Wbox code recently,
nobody with half a hair of sense on their head will want to ever touch
that thing again.

It's a security nightmare, and that's the best part of it.