RE: [PATCH 07/13] x86/kconfig/64: Enable more virtualization guest options in the defconfig: enable Xen, Xen_PVH, Jailhouse, ACRN, Intel TDX and Hyper-V

[Michael Kelley]

From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Sent: Saturday, June 14, 2025 3:31 AM
> 
> On Thu, May 15, 2025 at 11:40:06PM +0000, Michael Kelley wrote:
> > From: Ingo Molnar <mingo@xxxxxxxxxx> Sent: Thursday, May 15, 2025 6:27 AM
> > >
> > > Since the x86 defconfig aims to be a distro kernel work-alike with
> > > fewer drivers and a shorter build time, refresh all the virtualization
> > > guest Kconfig features, enabling paravirt spinlocks, and
> > > enabling the guest support code for the following guests:
> > >
> > >  - Xen
> > >  - Xen_PVH
> > >  - Jailhouse
> > >  - ACRN
> > >  - Intel TDX
> > >  - Hyper-V
> >
> > I built and tested a Hyper-V guest with defconfig. The Hyper-V storage
> > and keyboard drivers are pulled in automatically, so my previous
> > comment about them being "missing" is moot.
> >
> > But the Linux console for each Hyper-V guest is a synthetic graphics
> > console,
> 
> So clearly I'm a caveman like creature, but surely those things have
> serial console, right? I mean, that's how I access all my test boxes,
> serial console and ssh. What more does one really need :-)
> 
> /me crawls back into his cave.

When Hyper-V is set up with Windows 10/11 on a laptop/desktop,
or with Windows Server on a lab/datacenter server, the UI to a new
VM is always a graphics console. The VM does have a virtual UART
for the serial console, but it requires manual steps to map to a named
pipe on the Windows host, and then running something like PuTTY
against the named pipe. I do exactly that when debugging a Linux
boot problem, but otherwise it's less hassle to use the graphics
console to boot up, and then ssh into the VM.

It would be nice if Hyper-V had an option to set up new VMs with
a serial console by default, but I doubt that will ever happen. That's
Hyper-V's legacy as a hypervisor for running Windows guests. :-(

In an Azure cloud VM, Azure automatically does the steps to set
up the serial console, which appears in the Azure Portal. So there's
no additional hassle.

Michael