From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by finch.gentoo.org (Postfix) with ESMTPS id EB17E138206 for ; Wed, 3 Jan 2018 20:53:14 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 27947E0841; Wed, 3 Jan 2018 20:53:10 +0000 (UTC) Received: from mail-pg0-x241.google.com (mail-pg0-x241.google.com [IPv6:2607:f8b0:400e:c05::241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id B3BE8E0835 for ; Wed, 3 Jan 2018 20:53:09 +0000 (UTC) Received: by mail-pg0-x241.google.com with SMTP id q12so1130937pgt.7 for ; Wed, 03 Jan 2018 12:53:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to; bh=41oMYDoratEj4kE+hSWd2HCGLWg3uHbB+EkIFvyAIkI=; b=XRAzKQeAm0ycZjbTIyug4cXhtW8vjeR/41cJPwwdu1SjDiXEWSTEBvVaUoPDUW/cyv RTfKffjGzoyfAZn2CVgqWwZfOC0att6ebqpiIi0gkmZ7nCRFb78+m/GIAdBxnFiztyfi 6h8cp2KlvaUZFoYbvfkXHfxW1V6AH16KpFDB9v5ryb6+Rh+koRKaSfegt7LjZm8bHlFL FKfkMAXW3EcBmIKY1/DFyR0rzez4baZErCXh1oL3scrkNizUyMl6LQGrdcw0VA47l9f+ IAzie4AGf2SOTOjjg41wITOZev4X/+Sq8guPoJxe6FoS8AsYF0MX9YFzKCNAr5RCGDWq XoLw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to; bh=41oMYDoratEj4kE+hSWd2HCGLWg3uHbB+EkIFvyAIkI=; b=l4Ef7iF20afDpXeM9bYLcLZWNN8J5rzgyPgQfStVDwiqZpuVkIbHvPvlHShB5Dp6pu ocBdp9rnqHcmwnAtfwESOkmkMkt6bFVKpCZDg7x9FGKtveKIr958e4ocN4g2MrZobOGb 16y+xS+kopyAMA2mUw0rsqr5OWtLobPr0FLd5K4v5Ux9AQyXzGUSqQlR65ViOlQ/FJ0O VQvtV70C3FazdJJMnFBkRcpLqnpu92m4i27Pxbwlw+G+XfwktFhrciYkBcv/mvuIz89u x0eFnJzl92v6mtiox0y964keylBnjGpJqSUFriALyrl4sjJzPjxkAyTA+FVQtsq389U1 iifA== X-Gm-Message-State: AKGB3mKNdgwoDSutUaHFMF1nEQjQqtT/9BBkpjOF57QcRcTMypYwGPla sR+N+3j6JJQi6Bc+6yjEgBhBWPJpCSicN9s9RUroU4RX X-Google-Smtp-Source: ACJfBotzPMJO2WtobMeBaL0Kanb3NzltEAri5L38J9qVhRk/BLwAVruNbpqh94tJC5CUA/kOkZHuNYT2/wlcX3jUHMc= X-Received: by 10.101.67.2 with SMTP id j2mr2235619pgq.242.1515012788192; Wed, 03 Jan 2018 12:53:08 -0800 (PST) Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 Sender: freemanrich@gmail.com Received: by 10.100.151.169 with HTTP; Wed, 3 Jan 2018 12:53:07 -0800 (PST) In-Reply-To: <5A4D3E92.5010908@youngman.org.uk> References: <2CA973AB-B583-4F4F-A0B3-0FE347A672BD@stellar.eclipse.co.uk> <5A4D3E92.5010908@youngman.org.uk> From: Rich Freeman Date: Wed, 3 Jan 2018 15:53:07 -0500 X-Google-Sender-Auth: sNX1sJr0V3Tjtwao5UbDqJK968Q Message-ID: Subject: Re: [gentoo-user] Re: old kernels are installed during the upgrade To: gentoo-user@lists.gentoo.org Content-Type: text/plain; charset="UTF-8" X-Archives-Salt: d7323331-99ec-4716-ac45-f785ecda6438 X-Archives-Hash: 92572a4502fda92b1043a5bba8242670 On Wed, Jan 3, 2018 at 3:35 PM, Wols Lists wrote: > > And as I understand it the code can be disabled with either a compile > time option or command line switch to the kernel. I suspect the compile-time option is PAGE_TABLE_ISOLATION (which was newly added in 4.14.11). The command line option nopti will disable it at runtime. Rumor has it that it will be disabled on AMD CPUs in 4.14.12, but I can't point to anywhere authoritative for that news so I'd consider it a rumor. I've also heard that Arch has deployed it early to 4.14.11, and I wouldn't be surprised if many distros do this if it is intended to go into the next stable, as there would be no point subjecting AMD users to performance issues. I haven't spoken to the Gentoo kernel team about what their plans are for it. In any case, nopti on the command line is probably the cleanest solution. I personally avoided disabling the feature in the compiled kernel because I don't want to be using the same config file on an Intel CPU in a year or two and forget I have it forced off. > The relevant code is > called KAISER, which forces kernel and user address space into different > contexts, and causes a nasty context-switching overhead on both Intel > and AMD cpus. > I believe the kernel went with "Page Table Isolation (PTI)" rather that KAISER, probably to avoid ethnic issues. Apparently this was deemed to have a more acceptable acronym than Forcefully Unmap Complete Kernel With Interrupt Trampolines. -- Rich