linux-kernel - Re: [PATCH 02/16] x86/entry/32: Enter the kernel via trampoline stack

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Message-ID: <alpine.DEB.2.20.1801162117330.2366@nanos>
Date:   Tue, 16 Jan 2018 21:30:14 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Joerg Roedel <joro@...tes.org>
cc:     Ingo Molnar <mingo@...nel.org>, "H . Peter Anvin" <hpa@...or.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Brian Gerst <brgerst@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Eduardo Valentin <eduval@...zon.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>, aliguori@...zon.com,
        daniel.gruss@...k.tugraz.at, hughd@...gle.com, keescook@...gle.com,
        Andrea Arcangeli <aarcange@...hat.com>,
        Waiman Long <llong@...hat.com>, jroedel@...e.de
Subject: Re: [PATCH 02/16] x86/entry/32: Enter the kernel via trampoline
 stack

On Tue, 16 Jan 2018, Joerg Roedel wrote:
> @@ -89,13 +89,9 @@ static inline void refresh_sysenter_cs(struct thread_struct *thread)
>  /* This is used when switching tasks or entering/exiting vm86 mode. */
>  static inline void update_sp0(struct task_struct *task)
>  {
> -	/* On x86_64, sp0 always points to the entry trampoline stack, which is constant: */
> -#ifdef CONFIG_X86_32
> -	load_sp0(task->thread.sp0);
> -#else
> +	/* sp0 always points to the entry trampoline stack, which is constant: */
>  	if (static_cpu_has(X86_FEATURE_XENPV))
>  		load_sp0(task_top_of_stack(task));
> -#endif
>  }
>  
>  #endif /* _ASM_X86_SWITCH_TO_H */
> diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
> index 654229bac2fc..7270dd834f4b 100644
> --- a/arch/x86/kernel/asm-offsets_32.c
> +++ b/arch/x86/kernel/asm-offsets_32.c
> @@ -47,9 +47,11 @@ void foo(void)
>  	BLANK();
>  
>  	/* Offset from the sysenter stack to tss.sp0 */
> -	DEFINE(TSS_sysenter_stack, offsetof(struct cpu_entry_area, tss.x86_tss.sp0) -
> +	DEFINE(TSS_sysenter_stack, offsetof(struct cpu_entry_area, tss.x86_tss.sp1) -
>  	       offsetofend(struct cpu_entry_area, entry_stack_page.stack));
>  
> +	OFFSET(TSS_sp1, tss_struct, x86_tss.sp1);

Can you please split out the change of TSS_sysenter_stack into a separate
patch?

Other than that, this looks good.

Thanks,

	tglx