linux-kernel - Re: [RFC PATCH 00/62] Linux as SEV-ES Guest Support

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Date:   Tue, 11 Feb 2020 14:12:04 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Peter Zijlstra <peterz@...radead.org>, X86 ML <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        Linux Virtualization <virtualization@...ts.linux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [RFC PATCH 00/62] Linux as SEV-ES Guest Support

On Tue, Feb 11, 2020 at 7:43 AM Joerg Roedel <joro@...tes.org> wrote:
>
> On Tue, Feb 11, 2020 at 03:50:08PM +0100, Peter Zijlstra wrote:
>
> > Oh gawd; so instead of improving the whole NMI situation, AMD went and
> > made it worse still ?!?
>
> Well, depends on how you want to see it. Under SEV-ES an IRET will not
> re-open the NMI window, but the guest has to tell the hypervisor
> explicitly when it is ready to receive new NMIs via the NMI_COMPLETE
> message.  NMIs stay blocked even when an exception happens in the
> handler, so this could also be seen as a (slight) improvement.
>

I don't get it.  VT-x has a VMCS bit "Interruptibility
state"."Blocking by NMI" that tracks the NMI masking state.  Would it
have killed AMD to solve the problem they same way to retain
architectural behavior inside a SEV-ES VM?

--Andy