From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aurelien Jarno Subject: Re: [Qemu-devel] [PATCH v5 10/12] hw/mips: malta: Add KVM support Date: Fri, 20 Jun 2014 11:10:47 +0200 Message-ID: <20140620091047.GC13901@ohm.rr44.fr> References: <1403043037-1271-1-git-send-email-james.hogan@imgtec.com> <1403043037-1271-11-git-send-email-james.hogan@imgtec.com> <20140619162748.GO7398@ohm.rr44.fr> <577D5B21-4F8B-4A9A-BD25-A76C76987544@kymasys.com> <20140619214733.GJ24904@hall.aurel32.net> <786372578.29668656.1403244425225.JavaMail.zimbra@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Sanjay Lal , James Hogan , qemu-devel@nongnu.org, Peter Maydell , kvm@vger.kernel.org, Gleb Natapov To: Paolo Bonzini Return-path: Received: from hall.aurel32.net ([195.154.112.97]:42778 "EHLO hall.aurel32.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754539AbaFTJLD (ORCPT ); Fri, 20 Jun 2014 05:11:03 -0400 Content-Disposition: inline In-Reply-To: <786372578.29668656.1403244425225.JavaMail.zimbra@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Fri, Jun 20, 2014 at 02:07:05AM -0400, Paolo Bonzini wrote: >=20 >=20 > ----- Messaggio originale ----- > > Da: "Aurelien Jarno" > > A: "Sanjay Lal" > > Cc: "James Hogan" , qemu-devel@nongnu.org, = "Peter Maydell" , > > kvm@vger.kernel.org, "Gleb Natapov" , "Paolo Bonzi= ni" > > Inviato: Gioved=EC, 19 giugno 2014 23:47:34 > > Oggetto: Re: [Qemu-devel] [PATCH v5 10/12] hw/mips: malta: Add KVM = support > >=20 > > On Thu, Jun 19, 2014 at 12:34:24PM -0700, Sanjay Lal wrote: > > >=20 > > > On Jun 19, 2014, at 9:27 AM, Aurelien Jarno wrote: > > >=20 > > > > On Tue, Jun 17, 2014 at 11:10:35PM +0100, James Hogan wrote: > > > >> In KVM mode the bootrom is loaded and executed from the last 1= MB of > > > >> DRAM. > > > >=20 > > > > What is the reason for that? I am not opposed to that, but if i= t is > > > > really needed, it means that loading a bootloader into the flas= h area > > > > (for example YAMON) won't work and that this should be forbidde= n to the > > > > user. > > > >=20 > > >=20 > > > In trap and emulate mode, both the kernel and userland run in use= r mode on > > > the processor. Virtual addresses >=3D 0x80000000 are only accessi= ble in > > > kernel mode, and the default flash area (VA: 0xbfc00000/PA: 0x1fc= 00000) > > > falls in this range. > > >=20 > > > We therefore decided to relocate the bootloader to the last 1MB o= f RAM. > > > This area is excluded from the RAM ranges supplied to the kernel,= so it > > > should not be accessible to the user. > > >=20 > >=20 > > Thanks for the explanation. It means we should disable the support = for > > booting from the flash (using -pflash) in KVM mode, as it would sim= ply > > not work. >=20 > My idea was to add a machines-specific option umkernel=3Don, and requ= ire it > in order to run KVM. Later we can add umkernel=3Don support for TCG = as well, > while umkernel=3Doff with KVM requires virtualization extensions. >=20 > The same option can disable pflash boot. >=20 > What do you think? =46or what I understand the current KVM support in MIPS uses trap and emulate and thus doesn't need hardware support, just a recent kernel with the option enabled. That's why I do wonder if there is a real poin= t in supporting UM kernels in TCG mode. --=20 Aurelien Jarno GPG: 4096R/1DDD8C9B aurelien@aurel32.net http://www.aurel32.net From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34561) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wxuqe-0001MP-Qg for qemu-devel@nongnu.org; Fri, 20 Jun 2014 05:11:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wxuqa-00040J-So for qemu-devel@nongnu.org; Fri, 20 Jun 2014 05:11:04 -0400 Received: from hall.aurel32.net ([2001:bc8:30d7:101::1]:35682) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wxuqa-000408-N4 for qemu-devel@nongnu.org; Fri, 20 Jun 2014 05:11:00 -0400 Date: Fri, 20 Jun 2014 11:10:47 +0200 From: Aurelien Jarno Message-ID: <20140620091047.GC13901@ohm.rr44.fr> References: <1403043037-1271-1-git-send-email-james.hogan@imgtec.com> <1403043037-1271-11-git-send-email-james.hogan@imgtec.com> <20140619162748.GO7398@ohm.rr44.fr> <577D5B21-4F8B-4A9A-BD25-A76C76987544@kymasys.com> <20140619214733.GJ24904@hall.aurel32.net> <786372578.29668656.1403244425225.JavaMail.zimbra@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <786372578.29668656.1403244425225.JavaMail.zimbra@redhat.com> Subject: Re: [Qemu-devel] [PATCH v5 10/12] hw/mips: malta: Add KVM support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Peter Maydell , James Hogan , kvm@vger.kernel.org, Gleb Natapov , qemu-devel@nongnu.org, Sanjay Lal On Fri, Jun 20, 2014 at 02:07:05AM -0400, Paolo Bonzini wrote: > > > ----- Messaggio originale ----- > > Da: "Aurelien Jarno" > > A: "Sanjay Lal" > > Cc: "James Hogan" , qemu-devel@nongnu.org, "Peter Maydell" , > > kvm@vger.kernel.org, "Gleb Natapov" , "Paolo Bonzini" > > Inviato: Giovedì, 19 giugno 2014 23:47:34 > > Oggetto: Re: [Qemu-devel] [PATCH v5 10/12] hw/mips: malta: Add KVM support > > > > On Thu, Jun 19, 2014 at 12:34:24PM -0700, Sanjay Lal wrote: > > > > > > On Jun 19, 2014, at 9:27 AM, Aurelien Jarno wrote: > > > > > > > On Tue, Jun 17, 2014 at 11:10:35PM +0100, James Hogan wrote: > > > >> In KVM mode the bootrom is loaded and executed from the last 1MB of > > > >> DRAM. > > > > > > > > What is the reason for that? I am not opposed to that, but if it is > > > > really needed, it means that loading a bootloader into the flash area > > > > (for example YAMON) won't work and that this should be forbidden to the > > > > user. > > > > > > > > > > In trap and emulate mode, both the kernel and userland run in user mode on > > > the processor. Virtual addresses >= 0x80000000 are only accessible in > > > kernel mode, and the default flash area (VA: 0xbfc00000/PA: 0x1fc00000) > > > falls in this range. > > > > > > We therefore decided to relocate the bootloader to the last 1MB of RAM. > > > This area is excluded from the RAM ranges supplied to the kernel, so it > > > should not be accessible to the user. > > > > > > > Thanks for the explanation. It means we should disable the support for > > booting from the flash (using -pflash) in KVM mode, as it would simply > > not work. > > My idea was to add a machines-specific option umkernel=on, and require it > in order to run KVM. Later we can add umkernel=on support for TCG as well, > while umkernel=off with KVM requires virtualization extensions. > > The same option can disable pflash boot. > > What do you think? For what I understand the current KVM support in MIPS uses trap and emulate and thus doesn't need hardware support, just a recent kernel with the option enabled. That's why I do wonder if there is a real point in supporting UM kernels in TCG mode. -- Aurelien Jarno GPG: 4096R/1DDD8C9B aurelien@aurel32.net http://www.aurel32.net