linux-kernel - Re: [PATCH 30/62] x86/head/64: Move early exception dispatch to C code

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Date:   Tue, 11 Feb 2020 14:44:45 -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 30/62] x86/head/64: Move early exception dispatch to C code

On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro@...tes.org> wrote:
>
> From: Joerg Roedel <jroedel@...e.de>
>
> Move the assembly coded dispatch between page-faults and all other
> exceptions to C code to make it easier to maintain and extend.
>
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
>  arch/x86/kernel/head64.c  | 20 ++++++++++++++++++++
>  arch/x86/kernel/head_64.S | 11 +----------
>  2 files changed, 21 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 7cdfb7113811..d83c62ebaa85 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -36,6 +36,8 @@
>  #include <asm/microcode.h>
>  #include <asm/kasan.h>
>  #include <asm/fixmap.h>
> +#include <asm/extable.h>
> +#include <asm/trap_defs.h>
>
>  /*
>   * Manage page tables very early on.
> @@ -377,6 +379,24 @@ int __init early_make_pgtable(unsigned long address)
>         return __early_make_pgtable(address, pmd);
>  }
>
> +void __init early_exception(struct pt_regs *regs, int trapnr)
> +{
> +       unsigned long cr2;
> +       int r;

How about int (or bool) handled;  Or just if (!early_make_pgtable)
return;  This would also be nicer if you inverted the return value so
that true means "I handled it".

--Andy