linux-kernel - Re: [PATCH 38/62] x86/sev-es: Handle instruction fetches from user-space

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Date:   Tue, 17 Mar 2020 14:34:22 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     Andy Lutomirski <luto@...nel.org>, Joerg Roedel <joro@...tes.org>,
        X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        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>
Subject: Re: [PATCH 38/62] x86/sev-es: Handle instruction fetches from user-space

On Fri, Mar 13, 2020 at 2:12 AM Joerg Roedel <jroedel@...e.de> wrote:
>
> On Wed, Feb 12, 2020 at 01:42:48PM -0800, Andy Lutomirski wrote:
> > I realize that this is a somewhat arbitrary point in the series to
> > complain about this, but: the kernel already has infrastructure to
> > decode and fix up an instruction-based exception.  See
> > fixup_umip_exception().  Please refactor code so that you can share
> > the same infrastructure rather than creating an entirely new thing.
>
> Okay, but 'infrastructure' is a bold word for the call path down
> fixup_umip_exception().

I won't argue with that.

> It uses the in-kernel instruction decoder, which
> I already use in my patch-set. But I agree that some code in this
> patch-set is duplicated and already present in the instruction decoder,
> and that fixup_umip_exception() has more robust instruction decoding.
>
> I factor the instruction decoding part out and make is usable for the
> #VC handler too and remove the code that is already present in the
> instruction decoder.

Thanks!

>
> Regards,
>
>         Joerg
>