linux-kernel - Re: [PATCH v2 7/9] x86: Use current USER_CS to setup correct context on vmx entry

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Date:   Mon, 5 Oct 2020 12:54:11 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Gabriel Krisman Bertazi <krisman@...labora.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Christoph Hellwig <hch@....de>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Robert Richter <rric@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>, kernel@...labora.com
Subject: Re: [PATCH v2 7/9] x86: Use current USER_CS to setup correct context
 on vmx entry

On Sat, Oct 03, 2020 at 04:04:22PM -0700, Andy Lutomirski wrote:
> On Fri, Oct 2, 2020 at 5:15 PM Andy Lutomirski <luto@...nel.org> wrote:
> > But it's also more subtly wrong -- this corrupts all the segment attributes
> > in the case where a segment points to the GDT and the GDT attributes are
> > non-default.

Part of me wants to ask if it's even possible to get into such a scenario,
but a much larger part of me doesn't want to think about segmentation any
more :-)

> > I would also be okay with making the KVM code match the context switch
> > code, but this may be distinctly nontrivial.

Ya.
 
> If you're okay waiting for a couple days, I'll just do this.  I have
> it 2/3-done already, except I'm running into the utter catastrophe
> that is 32-bit stackprotector, so I'm going to fix that first.  (Or
> delete it if I get toosick of it.)

By all means.  I dragged my feet for several months, I can certainly do
nothing for a few more days.