linux-kernel - Re: [PATCH 1/3] x86/sev-es: Introduce from_syscall

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Message-ID: <20210217175939.GA6479@zn.tnic>
Date:   Wed, 17 Feb 2021 18:59:39 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Joerg Roedel <joro@...tes.org>
Cc:     x86@...nel.org, Joerg Roedel <jroedel@...e.de>,
        stable@...r.kernel.org, hpa@...or.com,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        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>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Martin Radev <martin.b.radev@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 1/3] x86/sev-es: Introduce from_syscall_gap() helper

I guess subject prefix should be "x86/traps:" but I'll fix that up while
applying eventually.

On Wed, Feb 17, 2021 at 01:01:41PM +0100, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
> 
> Introduce a helper to check whether an exception came from the syscall
> gap and use it in the SEV-ES code
> 
> Fixes: 315562c9af3d5 ("x86/sev-es: Adjust #VC IST Stack on entering NMI handler")
> Cc: stable@...r.kernel.org # 5.10+
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
>  arch/x86/include/asm/ptrace.h | 8 ++++++++
>  arch/x86/kernel/traps.c       | 3 +--
>  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
> index d8324a236696..14854b2c4944 100644
> --- a/arch/x86/include/asm/ptrace.h
> +++ b/arch/x86/include/asm/ptrace.h
> @@ -94,6 +94,8 @@ struct pt_regs {
>  #include <asm/paravirt_types.h>
>  #endif
>  
> +#include <asm/proto.h>
> +
>  struct cpuinfo_x86;
>  struct task_struct;
>  
> @@ -175,6 +177,12 @@ static inline bool any_64bit_mode(struct pt_regs *regs)
>  #ifdef CONFIG_X86_64
>  #define current_user_stack_pointer()	current_pt_regs()->sp
>  #define compat_user_stack_pointer()	current_pt_regs()->sp
> +
> +static inline bool from_syscall_gap(struct pt_regs *regs)

rip_within_syscall_gap() sounds kinda better to me and it is more
readable when you look at it at the usage site:

	if (rip_within_syscall_gap(regs))
		...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette