On 24.02.26 12:14, Roger Pau Monné wrote:
On Tue, Feb 24, 2026 at 10:51:35AM +0000, Teddy Astie wrote:It's currently possible to build Linux with CONFIG_PVH|CONFIG_XEN_PVHVM and no CONFIG_XEN_PVH. 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.So the current CONFIG_PVH selection done by CONFIG_XEN_PVH is moot?
No, it isn't. CONFIG_PVH is the common base needed for Xen and KVM guests to be able to run in PVH mode.
Keep CONFIG_XEN_PVH as a shortcut to enable PVH boot, ACPI support and PVHVM. Signed-off-by: Teddy Astie <[email protected]> --- Cc: Juergen Gross <[email protected]> Cc: Boris Ostrovsky <[email protected]> Cc: Oleksandr Tyshchenko <[email protected]> A tentative patch, I'm not sure of the way of dealing with the KConfig part, keeping CONFIG_XEN_PVH as a shortcut is interesting, but there may be other options. There are widespreadly used Linux distributions that have a similar configuration to this one, thus exhibit this issue i.e fail to boot.Do you know the underlying cause of not enabling CONFIG_XEN_PVH? Is the default set to n on the defconfig? Or are distros specifically disabling this option on purpose? It seems like a step backwards to merge this into some bigger generic option, we always try to fine-grain as much as possible. Maybe you could introduce XEN_HVM meta option, that selects both PVHVM and PVH?
No, please don't use "HVM" for that purpose. If anything I'd set the CONFIG_XEN_PVH default to that of CONFIG_XEN_PVHVM. Juergen
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