Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752623AbbDUIg3 (ORCPT ); Tue, 21 Apr 2015 04:36:29 -0400 Received: from mail.emea.novell.com ([130.57.118.101]:42268 "EHLO mail.emea.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751193AbbDUIgX convert rfc822-to-8bit (ORCPT ); Tue, 21 Apr 2015 04:36:23 -0400 Message-Id: <553628240200007800074272@mail.emea.novell.com> X-Mailer: Novell GroupWise Internet Agent 14.0.1 Date: Tue, 21 Apr 2015 09:36:20 +0100 From: "Jan Beulich" To: "Andrew Cooper" Cc: "David Vrabel" , , "Thomas Gleixner" , , "Xen-devel" , "Boris Ostrovsky" , "Ingo Molnar" , "Rusty Russell" , , "H. Peter Anvin" Subject: Re: [Xen-devel] [PATCH] [RFC] x86/cpu: Fix SMAP check in PVOPS environments References: <1429549782-12962-1-git-send-email-andrew.cooper3@citrix.com> In-Reply-To: <1429549782-12962-1-git-send-email-andrew.cooper3@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 887 Lines: 19 >>> On 20.04.15 at 19:09, wrote: > A different approach, given the dual nature of the AC flag now is to gate > setup_smap() on a kernel rpl of 0. SMAP necessarily can't be used in a > paravirtual situation where the kernel runs in cpl > 0. "Can't" isn't true here - for 64-bit PV Xen guests, which already toggle between two page table variants for kernel and user mode, it would be possible (but perhaps expensive) to mimic the needed behavior by introducing a 3rd set of page tables, containing only the kernel mappings. You may recall that I had even posted an RFC patch to tat effect about a year ago. Jan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/