[RFT] KVM Planes on Linux 7.1 ready for testing

[RFT] KVM Planes on Linux 7.1 ready for testing

[Jörg Rödel]

Hi all,

An updated version of the KVM Planes patches is now ready for wider testing.
The branches are based on Linux v7.1-rc6 and QEMU 11.0.0. Before sending them
out I'd love to get more people from the COCONUT community test the changes and
report any problems or regressions agains the 6.11 version.

The Linux branch is here:

	https://github.com/joergroedel/linux/tree/kvm-planes-v7.1

The QEMU branch is here:

	https://github.com/joergroedel/qemu/tree/qemu-planes-linux-v7.1

Both need to be used together, the current QEMU svsm-igvm branch will not work
the kernel above.

For QEMU, there are some minor changes needed for the command line:

	- Add a device-plane=2 parameter to the machine specification

	- Use irq-chip=split

As an example, my QEMU command line starts like this:

         qemu-system-x86_64 \
             -enable-kvm \
             -cpu EPYC-v4 \
             -machine q35,confidential-guest-support=sev0,memory-backend=ram1,igvm-cfg=igvm0,kernel-irqchip=split,device-plane=2 \
             -object memory-backend-memfd,id=ram1,size=32G,share=true \
             -object sev-snp-guest,id=sev0,cbitpos=51,reduced-phys-bits=1 \
             -object igvm-cfg,id=igvm0,file=$IGVM_FILE \
              ...

If no major issues are reported, I plan to post these patches to the mailing
lists for KVM and QEMU by next week.

I plan to update the COCONUT-SVSM downstream branches for KVM and QEMU once
Linux 7.1 is released and regularily rebase the changes to newer kernel and
QEMU versions, also incoperating review feedback from upstream.

Known limitation: The direct-VMSA setting support we have in the 6.11 kernel is
not part of the KVM planes patches yet. I plan to send a separate patch-set for
this feature.

Happy testing!


-Joerg

Re: [RFT] KVM Planes on Linux 7.1 ready for testing

[Luigi Leonardi]

Hi Joerg,

On Tue, Jun 02, 2026 at 12:41:57PM +0200, Jörg Rödel wrote:
>Hi all,
>
>An updated version of the KVM Planes patches is now ready for wider testing.
>The branches are based on Linux v7.1-rc6 and QEMU 11.0.0. Before sending them
>out I'd love to get more people from the COCONUT community test the changes and
>report any problems or regressions agains the 6.11 version.
>
>The Linux branch is here:
>
>	https://github.com/joergroedel/linux/tree/kvm-planes-v7.1
>
>The QEMU branch is here:
>
>	https://github.com/joergroedel/qemu/tree/qemu-planes-linux-v7.1
>

I think commit `ACPI: Rebuild ACPI tables on every read` can be dropped, IIRC
this was necessary when SVSM consumed MADT from fw_cfg.

In `qdev: Add plane property`, in function `device_initfn`, dev->plane
should be set to `qdev_default_plane()`
see https://github.com/coconut-svsm/qemu/pull/31/changes/8fa10020cb97ced3151f67b842ecba57ef76765e

Luigi