linux-kernel - Re: [PATCH 62/62] x86/sev-es: Add NMI state tracking

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALCETrWV15+YTGsEwUHBSjT2MYappLANw4fQHjgZgei2UyV1JQ@mail.gmail.com>
Date:   Tue, 11 Feb 2020 14:50:29 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Joerg Roedel <joro@...tes.org>
Cc:     X86 ML <x86@...nel.org>, "H. Peter Anvin" <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>,
        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: [PATCH 62/62] x86/sev-es: Add NMI state tracking

On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro@...tes.org> wrote:
>
> From: Joerg Roedel <jroedel@...e.de>
>
> Keep NMI state in SEV-ES code so the kernel can re-enable NMIs for the
> vCPU when it reaches IRET.

This patch is overcomplicated IMO.  Just do the magic incantation in C
from do_nmi or from here:

        /*
         * For ease of testing, unmask NMIs right away.  Disabled by
         * default because IRET is very expensive.

If you do the latter, you'll need to handle the case where the NMI
came from user mode.

The ideal solution is do_nmi, I think.

if (static_cpu_has(X86_BUG_AMD_FORGOT_ABOUT_NMI))
  sev_es_unmask_nmi();

Feel free to use X86_FEATURE_SEV_ES instead :)

--Andu