On 26.04.2013, at 13:04, Pranavkumar Sawargaonkar wrote: > This patch-set implements early printk support for virtio console devices without using any hypercalls. > > The current virtio early printk code in kernel expects that hypervisor will provide some mechanism generally a hypercall to support early printk. This patch-set does not break existing hypercall based early print support. > > This implementation adds: > 1. Early writeonly register named early_wr in virtio console's config space. > 2. Host feature flags namely VIRTIO_CONSOLE_F_EARLY_WRITE for telling guest about early-write capability in console device. > > Early write mechanism: > 1. When a guest wants to out some character, it has to simply write the character to early_wr register in config space of virtio console device. I won't nack this patch set, but I'll definitely express that I'm not happy with it. MMIO registers are handled by a different layer than the virtio console itself. After the virtio refactoring in QEMU, they will be completely separate drivers. So we'll be in a similar mess with early printk as we are on the s390-virtio machine, where early printk is done through hypercalls and thus we can't directly link it to the console output. I still don't see what the issue is with just implementing a small irq-less virtio driver for early printk. Alex _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
