Re: [PATCH v3 28/28] docs: update Xen-on-KVM documentation

David Woodhouse
2023-10-25T18:27:37Z

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On Wed, 2023-10-25 at 13:20 -0500, Eric Blake wrote:
> On Wed, Oct 25, 2023 at 03:50:42PM +0100, David Woodhouse wrote:
> > From: David Woodhouse <dwmw@amazon.co.uk>
> >
> > Add notes about console and network support, and how to launch PV guests.
> > Clean up the disk configuration examples now that that's simpler, and
> > remove the comment about IDE unplug on q35/AHCI now that it's fixed.
> >
> > Also update stale avocado test filename in MAINTAINERS.
> >
> > Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> > ---
> > +Xen paravirtual devices
> > +-----------------------
> > +
> > +The Xen PCI platform device is enabled automatically for a Xen guest. This
> > +allows a guest to unplug all emulated devices, in order to use paravirtual
> > +block and network drivers instead.
> > +
> > +Those paravirtual Xen block, network (and console) devices can be created
> > +through the command line, and/or hot-plugged.
> > +
> > +To provide a Xen console device, define a character device and then a device
> > +of type ``xen-console`` to connect to it. For the Xen console equivalent of
> > +the handy ``-serial mon:stdio`` option, for example:
> > +
> > +.. parsed-literal::
> > +   -chardev -chardev stdio,mux=on,id=char0,signal=off -mon char0 \\
> > +   -device xen-console,chardev=char0
>
> Is -chardev supposed to appear twice here?

It is not. Will fix; thanks.

> ...
> > +
> > +Booting Xen PV guests
> > +---------------------
> > +
> > +Booting PV guest kernels is possible by using the Xen PV shim (a version of Xen
> > +itself, designed to run inside a Xen HVM guest and provide memory management
> > +services for one guest alone).
> > +
> > +The Xen binary is provided as the ``-kernel`` and the guest kernel itself (or
> > +PV Grub image) as the ``-initrd`` image, which actually just means the first
> > +multiboot "module". For example:
> > +
> > +.. parsed-literal::
> > +
> > +  |qemu_system| --accel kvm,xen-version=0x40011,kernel-irqchip=split \\
> > +       -chardev stdio,id=char0 -device xen-console,chardev=char0 \\
> > +       -display none  -m 1G  -kernel xen -initrd bzImage \\
> > +       -append "pv-shim console=xen,pv -- console=hvc0 root=/dev/xvda1" \\
> > +       -drive file=${GUEST_IMAGE},if=xen
>
> Is the space between -- and console= intentionsl?

Yes, that one is correct. The -- is how you separate Xen's command line
(on the left) from the guest kernel command line (on the right).

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