From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 012D5C433EF for ; Tue, 7 Sep 2021 17:10:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D7CF1610C9 for ; Tue, 7 Sep 2021 17:10:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345606AbhIGRLJ (ORCPT ); Tue, 7 Sep 2021 13:11:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:39836 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345505AbhIGRLI (ORCPT ); Tue, 7 Sep 2021 13:11:08 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C0F4560187; Tue, 7 Sep 2021 17:10:01 +0000 (UTC) Received: from 82-132-222-194.dab.02.net ([82.132.222.194] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mNebf-009RVV-QZ; Tue, 07 Sep 2021 18:10:00 +0100 Date: Tue, 07 Sep 2021 18:09:58 +0100 Message-ID: <87bl54cnx5.wl-maz@kernel.org> From: Marc Zyngier To: Peter Maydell Cc: QEMU Developers , Andrew Jones , Eric Auger , kvmarm , kvm-devel , Android Kernel Team Subject: Re: [PATCH 3/3] docs/system/arm/virt: Fix documentation for the 'highmem' option In-Reply-To: References: <20210822144441.1290891-1-maz@kernel.org> <20210822144441.1290891-4-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 82.132.222.194 X-SA-Exim-Rcpt-To: peter.maydell@linaro.org, qemu-devel@nongnu.org, drjones@redhat.com, eric.auger@redhat.com, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi Peter, On Tue, 07 Sep 2021 13:51:13 +0100, Peter Maydell wrote: > > On Sun, 22 Aug 2021 at 15:45, Marc Zyngier wrote: > > > > The documentation for the 'highmem' option indicates that it controls > > the placement of both devices and RAM. The actual behaviour of QEMU > > seems to be that RAM is allowed to go beyond the 4GiB limit, and > > that only devices are constraint by this option. > > > > Align the documentation with the actual behaviour. > > I think it would be better to align the behaviour with the documentation. > > The intent of 'highmem' is to allow a configuration for use with guests > that can't address more than 32 bits (originally, 32-bit guests without > LPAE support compiled in). It seems like a bug that we allow the user > to specify more RAM than will fit into that 32-bit range. We should > instead make QEMU exit with an error if the user tries to specify > both highmem=off and a memory size that's too big to fit. I'm happy to address this if you are OK with the change in user visible behaviour. However, I am still struggling with my original goal, which is to allow QEMU to create a usable KVM_based VM on systems with a small IPA space (36 bits on the system I have). What would an acceptable way to convey this to the code that deals with the virt memory map so that it falls back to something that actually works? Thanks, M. -- Without deviation from the norm, progress is not possible. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D9567C433F5 for ; Tue, 7 Sep 2021 17:10:07 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 579D360187 for ; Tue, 7 Sep 2021 17:10:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 579D360187 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id E0DD54B1E0; Tue, 7 Sep 2021 13:10:06 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id KtAYaOm3HSky; Tue, 7 Sep 2021 13:10:04 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 876EF4B1F0; Tue, 7 Sep 2021 13:10:04 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id F00404B1FC for ; Tue, 7 Sep 2021 13:10:03 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id RnWCGJs4HOIQ for ; Tue, 7 Sep 2021 13:10:02 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id DA90E4B1CB for ; Tue, 7 Sep 2021 13:10:02 -0400 (EDT) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C0F4560187; Tue, 7 Sep 2021 17:10:01 +0000 (UTC) Received: from 82-132-222-194.dab.02.net ([82.132.222.194] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mNebf-009RVV-QZ; Tue, 07 Sep 2021 18:10:00 +0100 Date: Tue, 07 Sep 2021 18:09:58 +0100 Message-ID: <87bl54cnx5.wl-maz@kernel.org> From: Marc Zyngier To: Peter Maydell Subject: Re: [PATCH 3/3] docs/system/arm/virt: Fix documentation for the 'highmem' option In-Reply-To: References: <20210822144441.1290891-1-maz@kernel.org> <20210822144441.1290891-4-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 82.132.222.194 X-SA-Exim-Rcpt-To: peter.maydell@linaro.org, qemu-devel@nongnu.org, drjones@redhat.com, eric.auger@redhat.com, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: kvm-devel , QEMU Developers , Android Kernel Team , kvmarm X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi Peter, On Tue, 07 Sep 2021 13:51:13 +0100, Peter Maydell wrote: > > On Sun, 22 Aug 2021 at 15:45, Marc Zyngier wrote: > > > > The documentation for the 'highmem' option indicates that it controls > > the placement of both devices and RAM. The actual behaviour of QEMU > > seems to be that RAM is allowed to go beyond the 4GiB limit, and > > that only devices are constraint by this option. > > > > Align the documentation with the actual behaviour. > > I think it would be better to align the behaviour with the documentation. > > The intent of 'highmem' is to allow a configuration for use with guests > that can't address more than 32 bits (originally, 32-bit guests without > LPAE support compiled in). It seems like a bug that we allow the user > to specify more RAM than will fit into that 32-bit range. We should > instead make QEMU exit with an error if the user tries to specify > both highmem=off and a memory size that's too big to fit. I'm happy to address this if you are OK with the change in user visible behaviour. However, I am still struggling with my original goal, which is to allow QEMU to create a usable KVM_based VM on systems with a small IPA space (36 bits on the system I have). What would an acceptable way to convey this to the code that deals with the virt memory map so that it falls back to something that actually works? Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 01978C433EF for ; Tue, 7 Sep 2021 17:11:25 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A504860238 for ; Tue, 7 Sep 2021 17:11:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org A504860238 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:45226 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mNed1-0003qX-QN for qemu-devel@archiver.kernel.org; Tue, 07 Sep 2021 13:11:23 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41050) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mNebm-0002Rf-O7 for qemu-devel@nongnu.org; Tue, 07 Sep 2021 13:10:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:54608) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mNebk-0005V4-2Q for qemu-devel@nongnu.org; Tue, 07 Sep 2021 13:10:06 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C0F4560187; Tue, 7 Sep 2021 17:10:01 +0000 (UTC) Received: from 82-132-222-194.dab.02.net ([82.132.222.194] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mNebf-009RVV-QZ; Tue, 07 Sep 2021 18:10:00 +0100 Date: Tue, 07 Sep 2021 18:09:58 +0100 Message-ID: <87bl54cnx5.wl-maz@kernel.org> From: Marc Zyngier To: Peter Maydell Subject: Re: [PATCH 3/3] docs/system/arm/virt: Fix documentation for the 'highmem' option In-Reply-To: References: <20210822144441.1290891-1-maz@kernel.org> <20210822144441.1290891-4-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 82.132.222.194 X-SA-Exim-Rcpt-To: peter.maydell@linaro.org, qemu-devel@nongnu.org, drjones@redhat.com, eric.auger@redhat.com, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Received-SPF: pass client-ip=198.145.29.99; envelope-from=maz@kernel.org; helo=mail.kernel.org X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrew Jones , kvm-devel , QEMU Developers , Eric Auger , Android Kernel Team , kvmarm Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Peter, On Tue, 07 Sep 2021 13:51:13 +0100, Peter Maydell wrote: > > On Sun, 22 Aug 2021 at 15:45, Marc Zyngier wrote: > > > > The documentation for the 'highmem' option indicates that it controls > > the placement of both devices and RAM. The actual behaviour of QEMU > > seems to be that RAM is allowed to go beyond the 4GiB limit, and > > that only devices are constraint by this option. > > > > Align the documentation with the actual behaviour. > > I think it would be better to align the behaviour with the documentation. > > The intent of 'highmem' is to allow a configuration for use with guests > that can't address more than 32 bits (originally, 32-bit guests without > LPAE support compiled in). It seems like a bug that we allow the user > to specify more RAM than will fit into that 32-bit range. We should > instead make QEMU exit with an error if the user tries to specify > both highmem=off and a memory size that's too big to fit. I'm happy to address this if you are OK with the change in user visible behaviour. However, I am still struggling with my original goal, which is to allow QEMU to create a usable KVM_based VM on systems with a small IPA space (36 bits on the system I have). What would an acceptable way to convey this to the code that deals with the virt memory map so that it falls back to something that actually works? Thanks, M. -- Without deviation from the norm, progress is not possible.