linux-kernel - Re: [PATCH] mm: Add new vma flag VM_LOCAL

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Message-ID: <20180515123542.GB12217@hirez.programming.kicks-ass.net>
Date:   Tue, 15 May 2018 14:35:42 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Boaz Harrosh <boazh@...app.com>,
        Matthew Wilcox <willy@...radead.org>,
        Jeff Moyer <jmoyer@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Rik van Riel <riel@...hat.com>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Amit Golander <Amit.Golander@...app.com>
Subject: Re: [PATCH] mm: Add new vma flag VM_LOCAL_CPU

On Tue, May 15, 2018 at 01:07:51PM +0100, Mark Rutland wrote:
> 					// speculatively allocates TLB

Ohh, right, I completely forgot about that, but that actually does
happen. We had trouble with AMD doing just that only about a year ago or
so IIRC.

CPUs are completely free to speculatively load TLB entries for pages
they never actually end up touching (typically prefetcher based), as
long as there's valid page-tables for them at the time.

So yes, you're right.