----- Messaggio originale ----- > Da: "Aurelien Jarno" <aurel...@aurel32.net> > A: "Sanjay Lal" <sanj...@kymasys.com> > Cc: "James Hogan" <james.ho...@imgtec.com>, qemu-devel@nongnu.org, "Peter > Maydell" <peter.mayd...@linaro.org>, > k...@vger.kernel.org, "Gleb Natapov" <g...@redhat.com>, "Paolo Bonzini" > <pbonz...@redhat.com> > 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 <aurel...@aurel32.net> 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? Paolo
