On Fri, Jun 20, 2014 at 02:07:05AM -0400, Paolo Bonzini wrote: > > > ----- Messaggio originale ----- > > Da: "Aurelien Jarno" <aurelien@xxxxxxxxxxx> > > A: "Sanjay Lal" <sanjayl@xxxxxxxxxxx> > > Cc: "James Hogan" <james.hogan@xxxxxxxxxx>, qemu-devel@xxxxxxxxxx, "Peter Maydell" <peter.maydell@xxxxxxxxxx>, > > kvm@xxxxxxxxxxxxxxx, "Gleb Natapov" <gleb@xxxxxxxxxx>, "Paolo Bonzini" <pbonzini@xxxxxxxxxx> > > 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 <aurelien@xxxxxxxxxxx> 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@xxxxxxxxxxx http://www.aurel32.net -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
