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Date:   Mon, 6 Apr 2020 05:23:43 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     LKML <linux-kernel@vger.kernel.org>, x86@kernel.org,
        "Kenneth R. Crudup" <kenny@panix.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Jessica Yu <jeyu@kernel.org>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Xiaoyao Li <xiaoyao.li@intel.com>,
        Nadav Amit <namit@vmware.com>,
        Thomas Hellstrom <thellstrom@vmware.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [patch 1/2] x86,module: Detect VMX modules and disable
 Split-Lock-Detect
Message-ID: <20200406122343.GA10683@infradead.org>
References: <20200402123258.895628824@linutronix.de>
 <20200402124205.242674296@linutronix.de>
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On Thu, Apr 02, 2020 at 02:32:59PM +0200, Thomas Gleixner wrote:
> From: Peter Zijlstra <peterz@infradead.org>
> 
> It turns out that with Split-Lock-Detect enabled (default) any VMX
> hypervisor needs at least a little modification in order to not blindly
> inject the #AC into the guest without the guest being ready for it.
> 
> Since there is no telling which module implements a hypervisor, scan the
> module text and look for the VMLAUNCH instruction. If found, the module is
> assumed to be a hypervisor of some sort and SLD is disabled.
> 
> Hypervisors, which have been modified and are known to work correctly,
> can add:
> 
>   MODULE_INFO(sld_safe, "Y");
> 
> to explicitly tell the module loader they're good.
> 
> NOTE: it is unfortunate that struct load_info is not available to the
>       arch module code, this means CONFIG_CPU_SUP_INTEL gunk is needed
>       in generic code.
> 
> NOTE: while we can 'trivially' fix KVM, we're still stuck with stuff
>       like VMware and VirtualBox doing their own thing.

This is just crazy.  We have never cared about any out tree module, why
would we care here where it creates a real complexity.  Just fix KVM
and ignore anything else.