Re: [PATCH 0/2] Early printk support for virtio console devices.

From: Anup Patel
Date: Fri Apr 26 2013 - 08:59:50 EST

On 26 April 2013 18:03, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Friday 26 April 2013 17:36:16 Anup Patel wrote:
>> On 26 April 2013 17:03, Peter Maydell <peter.maydell@xxxxxxxxxx> wrote:
>> > On 26 April 2013 12:19, Alexander Graf <agraf@xxxxxxx> wrote:
>> >> 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.
>> >
>> > Good point -- we don't really want to be mixing up the
>> > transport and the backend. You can see it in the kvmtool
>> > patch, in fact -- it introduces an "if this is virtio-console"
>> > special case into the mmio.c file which previously was
>> > entirely backend agnostic.
>> Well, we can always have virtio device specific config registers
>> handle by virtio device backends and generic virtio config register
>> handled by transport.
>> kvmtool patch is hacky because it does not provide virtio device
>> specific config read/write callbacks.
> Couldn't kvmtool implement the interface used by smh_printch()
> for early output instead?
> Or if that's not a fitting inteface, maybe a psci call for writing
> a character to the console?
> Arnd

I am curious about how smh-based or hypercall-based early prints would
be handled in following scenario:

"A board is running KVM ARM enabled kernel and linux console on serial
port. Now a user remotely connects to the board via telnet/ssh and
launches a VM with smh-based or hypercall-based earlyprintk."

In the above scenario, will smh-based or hypercall-based earlyprints
appear to user on remote shell or not ?

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