On Wed, May 01, 2013 at 07:53:49AM +0100, Anup Patel wrote: > On Wed, May 1, 2013 at 7:37 AM, Rusty Russell <ru...@rustcorp.com.au> wrote: > > Alexander Graf <ag...@suse.de> writes: > >> There are not device specific registers in > >> virtio-console. Virtio-console lives behind a virtio bus which doesn't > >> know what these registers are. > > > > You're not going to make coherent arguments without reading that actual > > patch we're discussing. And you're going to just waste everyone else's > > time. > > > >> Even if you shove it into config space, > > > > Which is what the patch does... > > > >> it'd be broken because config access happens without intercepts on > >> some platforms. > > > > But people keep assuming it, which is one reason virtio_ccw switched > > from passive lguest-style config to active. Only lguest and the old kvm > > virtio use it, and lguest can change. > > > > An emergency output is a reasonable idea, and this is a reasonable > > implementation. The question is practical: will it be used? Because we > > don't implement reasonable ideas which aren't going to be used. > > We are already using it for Guest bring-up on APM ARM64 board using > KVMTOOL and so far it has been really helpful in debugging KVM ARM64 > guest issues. > > Also, this is a very useful debugging method for Guest bring-up on > other architectures supported by KVM and other Hypervisors that > support VirtIO.
FWIW: I've hacked together a small set of patches allowing us to use the x86 ioport peripherals on arm/arm64 in kvmtool. This means you can use the 8250 for earlyprintk on the latter, and even as the main console if you like since it has a device-tree binding. I'll post the patches as an RFC to the kvm list. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
