Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755571Ab1EYLW0 (ORCPT ); Wed, 25 May 2011 07:22:26 -0400 Received: from service87.mimecast.com ([94.185.240.25]:35058 "HELO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751392Ab1EYLWZ convert rfc822-to-8bit (ORCPT ); Wed, 25 May 2011 07:22:25 -0400 Subject: Re: [PATCH v6 00/18] ARM: Add support for the Large Physical Address Extensions From: Catalin Marinas To: Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, Nicolas Pitre , David Brown , Russell King - ARM Linux , linux-kernel@vger.kernel.org In-Reply-To: <201105251310.39609.arnd@arndb.de> References: <1306273164-18217-1-git-send-email-catalin.marinas@arm.com> <8yapqn7fyab.fsf@huya.qualcomm.com> <201105251310.39609.arnd@arndb.de> Organization: ARM Limited Date: Wed, 25 May 2011 12:22:15 +0100 Message-ID: <1306322535.31249.14.camel@e102109-lin.cambridge.arm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 X-OriginalArrivalTime: 25 May 2011 11:22:31.0560 (UTC) FILETIME=[09B8E880:01CC1ACE] X-MC-Unique: 111052512222108301 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1905 Lines: 52 On Wed, 2011-05-25 at 12:10 +0100, Arnd Bergmann wrote: > On Wednesday 25 May 2011, Nicolas Pitre wrote: > > > Do you expect non LPAE targets to be able to boot with these changes > > > applied (and LPAE enabled)? I am able to build this tree for the > > > MSM8660 (with a minor patch below), but it fails to boot with LPAE > > > enabled. It seems to work fine with LPAE not enabled. > > > > I wouldn't expect a LPAE kernel to boot on non LPAE capable hardware. > > > > And I don't think we'll ever try to support both LPAE and non-LPAE modes > > in the same kernel binary either since this has implications all over > > the place in core kernel mm code. > > Just for information and to complete the picture, what other of these > combinations are possible? > > * Non-LPAE kernel on LPAE-capable hardware Works fine. The LPAE-capable processors like A15 support the classic page table format as well, it's only a configuration bit to switch to LPAE. > * LPAE kernel as KVM guest of LPAE kernel Should work when KVM for A15 becomes available > * non-LPAE kernel as KVM guest of LPAE kernel Same as above. KVM shouldn't care much about the underlying OS, it just sets up the IPA (Intermediate Physical Address) translations and you can have classic page tables on top. > * LPAE kernel as KVM guest of non-LPAE kernel No. KMV without LPAE uses a shadow page tables mechanism and I'm not aware of any plans to make it (guest) LPAE-aware. > * non-LPAE kernel as KVM guest of non-LPAE kernel on LPAE-enabled > hardware Would work as the current KVM implementation for ARMv7 with classic page tables (but I don't know what the status it). -- Catalin -- 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/