linux-kernel - Re: [patch V2 21/28] x86/speculation: Prepare for conditional IBPB in switch

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Message-ID: <alpine.DEB.2.21.1811252009260.1684@nanos.tec.linutronix.de>
Date:   Sun, 25 Nov 2018 20:11:01 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
cc:     x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Tom Lendacky <thomas.lendacky@....com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>,
        Waiman Long <longman9394@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Dave Stewart <david.c.stewart@...el.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [patch V2 21/28] x86/speculation: Prepare for conditional IBPB
 in switch_mm()

On Sun, 25 Nov 2018, Thomas Gleixner wrote:
>  /*
> + * Use bit 0 to mangle the TIF_SPEC_IB state into the mm pointer which is
> + * stored in cpu_tlb_state.last_user_mm_ibpb.
> + */
> +#define LAST_USER_MM_IBPB	0x1UL
> +
> +/*
> +	unsigned long next_tif = task_thread_info(next)->flags;
> +	unsigned long ibpb = (next_tif >> TIF_SPEC_IB) & LAST_USR_MM_IBPB;

That wants to be LAST_USER_ of course. That's what you get for last minute
changes...