From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH v5 10/12] hw/mips: malta: Add KVM support Date: Fri, 20 Jun 2014 02:07:05 -0400 (EDT) Message-ID: <786372578.29668656.1403244425225.JavaMail.zimbra@redhat.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: Peter Maydell , James Hogan , kvm@vger.kernel.org, Gleb Natapov , qemu-devel@nongnu.org, Sanjay Lal To: Aurelien Jarno Return-path: In-Reply-To: <20140619214733.GJ24904@hall.aurel32.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org List-Id: kvm.vger.kernel.org ----- 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: Gioved=C3=AC, 19 giugno 2014 23:47:34 > Oggetto: Re: [Qemu-devel] [PATCH v5 10/12] hw/mips: malta: Add KVM suppor= t >=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 wrot= e: > >=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 1MB of > > >> DRAM. > > >=20 > > > 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 t= he > > > user. > > >=20 > >=20 > > In trap and emulate mode, both the kernel and userland run in user mode= on > > the processor. Virtual addresses >=3D 0x80000000 are only accessible in > > kernel mode, and the default flash area (VA: 0xbfc00000/PA: 0x1fc00000) > > falls in this range. > >=20 > > 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. > >=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 simply > not work. My idea was to add a machines-specific option umkernel=3Don, and require it in order to run KVM. Later we can add umkernel=3Don support for TCG as wel= l, while umkernel=3Doff with KVM requires virtualization extensions. The same option can disable pflash boot. What do you think? Paolo