Re: [PATCH v1 3/6] xen/arm: create dom0less virtio-pci DT node

[Julien Grall <julien@xxxxxxx>]

Hi Edgar,

On 25/09/2024 17:34, Edgar E. Iglesias wrote:
> On Wed, Sep 25, 2024 at 08:44:41AM +0100, Julien Grall wrote:
> > Hi,
> > On 24/09/2024 17:23, Edgar E. Iglesias wrote:
> > > From: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
> > >
> > > When virtio-pci is specified in the dom0less domU properties, create a
> > > virtio-pci node in the guest's device tree. Set up an mmio handler with
> > > a register for the guest to poll when the backend has connected and
> > > virtio-pci bus is ready to be probed. Grant tables may be used by
> > > specifying virtio-pci = "grants";.
> > >
> > > [Edgar: Use GPEX PCI INTX interrupt swizzling (from PCI specs).
> > >    Make grants iommu-map cover the entire PCI bus.
> > >    Add virtio-pci-ranges to specify memory-map for direct-mapped guests.
> > >    Document virtio-pci dom0less fdt bindings.]
> > > Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
> > > Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xxxxxxx>
> > > ---
> > >    docs/misc/arm/device-tree/booting.txt |  21 +++
> > >    xen/arch/arm/dom0less-build.c         | 238 ++++++++++++++++++++++++++
> > >    xen/arch/arm/include/asm/kernel.h     |  15 ++
> > >    3 files changed, 274 insertions(+)
> > >
> > > diff --git a/docs/misc/arm/device-tree/booting.txt 
> > > b/docs/misc/arm/device-tree/booting.txt
> > > index 3a04f5c57f..82f3bd7026 100644
> > > --- a/docs/misc/arm/device-tree/booting.txt
> > > +++ b/docs/misc/arm/device-tree/booting.txt
> > > @@ -276,6 +276,27 @@ with the following properties:
> > >        passed through. This option is the default if this property is missing
> > >        and the user does not provide the device partial device tree for the 
> > > domain.
> > > +- virtio-pci
> > Similar question to the other patches, why is this specific to virtio PCI?
> > QEMU (or another device module) is free to emulate whatever it wants behind
> > the PCI hosbtridge.
> There's no hard limitatino to only virtio-pci devices it's more of a
> recommendation that PVH guests should not use "emulated" devices but
> there's nothing stopping it.
Could you provide a bit more details where this requirement is coming 
from? For instance, I would expect we would need to do some emulation to 
boot Windows on Arm.
Cheers,

--
Julien Grall