linux-kernel - Re: [patch 51/60] x86/mm: Allow flushing for future ASID switches

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Message-ID: <20171204230659.GG20227@worktop.programming.kicks-ass.net>
Date:   Tue, 5 Dec 2017 00:06:59 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Borislav Petkov <bpetkov@...e.de>,
        Greg KH <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...gle.com>,
        Hugh Dickins <hughd@...gle.com>,
        Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        David Laight <David.Laight@...lab.com>,
        Eduardo Valentin <eduval@...zon.com>, aliguori@...zon.com,
        Will Deacon <will.deacon@....com>,
        Daniel Gruss <daniel.gruss@...k.tugraz.at>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>, michael.schwarz@...k.tugraz.at,
        Borislav Petkov <bp@...en8.de>, moritz.lipp@...k.tugraz.at,
        richard.fellner@...dent.tugraz.at, Andrew Banman <abanman@....com>,
        mike.travis@....com
Subject: Re: [patch 51/60] x86/mm: Allow flushing for future ASID switches

On Mon, Dec 04, 2017 at 02:54:46PM -0800, Andy Lutomirski wrote:
> On Mon, Dec 4, 2017 at 2:47 PM, Peter Zijlstra <peterz@...radead.org> wrote:

> > As is __flush_tlb_single() does user and __flush_tlb_one() does
> > user+kernel.
> 
> Yep.  A one-liner above the function to that effect would make it
> *way* clearer what's going on.

Bah, since my notes are upstairs I actually got that wrong,
do_kernel_range_flush() also uses __flush_tlb_single(), but then it
finishes with invalidate_pcid_other(), so effectively it shoots down
world.

So we should probably switch do_kernel_range_flush() to
__flush_tlb_one() and tlb_uv.c (pending SGI approval) to
__flush_tlb_single().

I'll dig through my notes in the morning and do a patch with comments.