On 07/05/14 13:17, Peter Maydell wrote: > On 7 May 2014 12:04, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: >> On Wed, May 07 2014 at 11:40:54 am BST, Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx> wrote: >>> All the fuzz is not really about enforcing kernel access... PPC also >>> has a current endianness selector (MSR_LE) but it only makes sense >>> if you are in the cpu context. Initial versions of the virtio biendian >>> support for QEMU PPC64 used an arbitrary cpu: in this case, the >>> only sensible thing to look at to support kernel based virtio is the >>> interrupt endianness selector (LPCR_ILE), because if gives a safe >>> hint of the kernel endianness. >>> >>> The patch set has evolved and now uses current_cpu at device reset time. >>> As a consequence, we are not necessarily tied to the kernel LPCR_ILE >>> selector I guess. > > Ah yes, I'd forgotten the history behind why we ended up looking > at interrupt endianness. > >> That makes a lot of sense, thanks for explaining that. You're basically >> doing the exact same thing we do with kvmtool on ARM. So if we have >> similar architectural features on both sides, why don't we support both >> kernel and userspace access? > > I don't think that we really need to get into whether userspace > access is or is not a good idea -- "endianness of the CPU which > does the virtio reset at the point when it does that reset" is a > nice simple rule that should generalise across architectures, > so why make it more complicated than that? This definition looks pretty good to me. Simple and to the point. Thanks, M. -- Jazz is not dead. It just smells funny... -- 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
