linux-kernel - Re: [PATCH 50/62] x86/sev-es: Handle VMMCALL Events

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Message-Id: <DC865D59-CAD2-4D1C-919B-1C954B1EFFB1@amacapital.net>
Date:   Tue, 11 Feb 2020 16:14:53 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Joerg Roedel <joro@...tes.org>
Cc:     x86@...nel.org, hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        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>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH 50/62] x86/sev-es: Handle VMMCALL Events



> On Feb 11, 2020, at 5:53 AM, Joerg Roedel <joro@...tes.org> wrote:
> 
> From: Tom Lendacky <thomas.lendacky@....com>
> 
> Implement a handler for #VC exceptions caused by VMMCALL instructions.
> This patch is only a starting point, VMMCALL emulation under SEV-ES
> needs further hypervisor-specific changes to provide additional state.
> 

How about we just don’t do VMMCALL if we’re a SEV-ES guest?  Otherwise we add thousands of cycles of extra latency for no good reason.