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Re: [RFC PATCH] x86/xen: Consider Xen PVH support in CONFIG_XEN_PVHVM
- To: Jan Beulich <jbeulich@xxxxxxxx>, Teddy Astie <teddy.astie@xxxxxxxxxx>
- From: Jürgen Groß <jgross@xxxxxxxx>
- Date: Tue, 24 Feb 2026 12:13:29 +0100
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- Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
- Delivery-date: Tue, 24 Feb 2026 11:13:45 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 24.02.26 12:01, Jan Beulich wrote:
On 24.02.2026 11:51, Teddy Astie wrote:
It's currently possible to build Linux with CONFIG_PVH|CONFIG_XEN_PVHVM
and no CONFIG_XEN_PVH.
In which case, how can you expect Xen PVH to work?
I agree. Similar to a kernel not working properly on AMD when configured
to support INTEL cpus only.
That leads to inconsistent kernels that fails with
"Missing xen PVH initialization" when booting using PVH boot method or
display various errors and fail to initialize Xen PV drivers when booting
with PVH-GRUB.
platform_pci_unplug: Xen Platform PCI: unrecognised magic value
...
# modprobe xen-blkfront
modprobe: ERROR: could not insert 'xen_blkfront': No such device
# modprobe xen-netfront
modprobe: ERROR: could not insert 'xen_netfront': No such device
When built without CONFIG_XEN_PVH, PVH-specific logic is disabled, hence when
booting with e.g PVH-OVMF, Linux assumes we are a HVM guest, even when we aren't
actually one (in the "with HVM emulated devices" sense).
As it is actually possible to boot Xen PVH without CONFIG_PVH; and that most
Xen-related logic exist within CONFIG_XEN_PVHVM; consider PVH guests support
within CONFIG_XEN_PVHVM instead of CONFIG_XEN_PVH.
XEN_PVHVM serves a different purpose though, iirc.
I does.
CONFIG_XEN_PVH depends on CONFIG_XEN_PVHVM exactly because a lot of the
logic required for PVH mode was implemented as a performance tweak of HVM
under the CONFIG_XEN_PVHVM umbrella.
In case you want to boot as a working PVH guest, you need a kernel
configured with CONFIG_XEN_PVH. It is that simple.
Its a NACK from me.
Juergen
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