Re: [PATCH v1 5/5] i386: Hyper-V VMBus ACPI DSDT entry

[Roman Kagan <rvkagan@yandex-team.ru>]

On Wed, Apr 08, 2020 at 07:16:39AM +0300, Jon Doron wrote:
> On 07/04/2020, Maciej S. Szmigiero wrote:
> > On 07.04.2020 20:56, Roman Kagan wrote:
> > > On Mon, Apr 06, 2020 at 11:20:39AM +0300, Jon Doron wrote:
> > > > Well I want it to be merged in :-)
> > > 
> > > Hmm I'm curious why, it has little to offer over virtio.
> > > 
> > > Anyway the series you've posted seems to be based on a fairly old
> > > version.
> > > 
> > > The one in openvz repo is more recent.  It's still in need for
> > > improvement, too, but should be testable at least.
> 
> Well I have implemented the hyperv synthetic kernel debugger interface, but
> on Windows 10 it requires to have a working VMBus (it's not really using it,
> but without a function vmbus that will answer to the initiate contact then
> the kdnet will simply be stuck in a loop.

I see, thanks, I've never heard of this before.

> With the synthetic kernel debugger interface you can debug older OS (Win7 up
> to latest Win10). The benefit is that its much faster than all other
> interfaces.

I guess you compare it to debugging via serial port.  I wonder where the
difference comes from?  I thought the transport didn't require any
significant throughput, and latency-wise the (emulated) serial port was
just as good as any other.  Am I missing something?

Thanks,
Roman.

> In addition to that Michael Kelley from Microsoft has informed us that
> Microsoft might be dropped the synthetic kernel debugger interface sometime
> in the future, and it seems like the new mode is simply to use hvnet device
> for the communication (which is again much faster).
> 
> Cheers,
> -- Jon.
> > 
> > Isn't the one at
> > https://src.openvz.org/projects/UP/repos/qemu/commits?until=refs%2Fheads%2Fvmbus
> > the latest one?
> > 
> > It seems to be last changed in October 2019 - is there a
> > later one?
> > 
> > > Thanks,
> > > Roman.
> > 
> > Thanks,
> > Maciej