From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f72.google.com (mail-it0-f72.google.com [209.85.214.72]) by kanga.kvack.org (Postfix) with ESMTP id 1C1FB8E0001 for ; Tue, 11 Sep 2018 14:20:47 -0400 (EDT) Received: by mail-it0-f72.google.com with SMTP id u126-v6so12381073itb.0 for ; Tue, 11 Sep 2018 11:20:47 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id q11-v6sor11752857iop.216.2018.09.11.11.20.45 for (Google Transport Security); Tue, 11 Sep 2018 11:20:45 -0700 (PDT) MIME-Version: 1.0 References: <20180830205527.dmemjwxfbwvkdzk2@suse.de> <20180831070722.wnulbbmillxkw7ke@suse.de> <20180911114927.gikd3uf3otxn2ekq@suse.de> In-Reply-To: <20180911114927.gikd3uf3otxn2ekq@suse.de> From: Linus Torvalds Date: Tue, 11 Sep 2018 08:20:33 -1000 Message-ID: Subject: Re: 32-bit PTI with THP = userspace corruption Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Joerg Roedel Cc: Thomas Gleixner , Meelis Roos , Linux Kernel Mailing List , linux-mm , Andrea Arcangeli On Tue, Sep 11, 2018 at 1:49 AM Joerg Roedel wrote: > > I had a look into the THP and the HugeTLBfs code, and that is not > really easy to fix there. As I can see it now, there are a few options > to fix that, but most of them are ugly: Just do (4): disable PTI with PAE. Then we can try to make people perhaps not use !PAE very much, and warn if you have PAE disabled on a machine that supports it. As you say, there shouldn't be much of a performance impact from PAE. There is a more noticeable performance impact from HIGHMEM, not from HIGHMEM_64G, iirc. Linus