Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752500AbdFNRkl (ORCPT ); Wed, 14 Jun 2017 13:40:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:56736 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751624AbdFNRkj (ORCPT ); Wed, 14 Jun 2017 13:40:39 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EC853239BE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=luto@kernel.org MIME-Version: 1.0 In-Reply-To: <20170614124032.4159-4-brgerst@gmail.com> References: <20170614124032.4159-1-brgerst@gmail.com> <20170614124032.4159-4-brgerst@gmail.com> From: Andy Lutomirski Date: Wed, 14 Jun 2017 10:40:17 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 3/3] x86/xen: Move paravirt IOPL switching to slow the path To: Brian Gerst , Andrew Cooper Cc: X86 ML , "linux-kernel@vger.kernel.org" , Ingo Molnar , "H . Peter Anvin" , Juergen Gross , Boris Ostrovsky Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 415 Lines: 8 On Wed, Jun 14, 2017 at 5:40 AM, Brian Gerst wrote: > Since tasks using IOPL are very rare, move the switching code to the slow > path for lower impact on normal tasks. I think that Andrew Cooper added a vmassist that we could opt in to that makes Xen PV IOPL switching work more or less just like native. We could maybe opt in to that and avoid needing this stuff at all on newer hypervisors.