Re: KVM planes branches

On Mon, Jan 19, 2026 at 12:22 PM Carlos López <[email protected]> wrote:
>
> Hi,
>
> On 1/7/26 3:02 PM, Oliver Steffen wrote:
> > Hi everyone,
> > happy new year!
> >
> > I am curious about the state of the KVM planes effort and want
> > to experiment with it a bit.
> > I tried out the KVM planes branches we have in our GitHub org.
> > I built Qemu and the host kernel from there and I am able to launch
> > the current SVSM with that. QEMU just needed the patch for MADT-via-IGVM.
> > But the OVMF does not seem to start. All I see is
> >
> > ...
> > [SVSM] VTPM: TPM 2.0 Reference Implementation initialized
> > [SVSM] [CPU 0] Virtual memory pages used: 0 * 4K, 0 * 2M
> > [SVSM] VMSA PA: 0x8000f49000
> > [SVSM] Launching Firmware
> > [init] COCONUT-SVSM init process starting
> > [SVSM] Terminating task init, exit_code 0
> > [SVSM] Launching request-processing task on CPU 1
> > [SVSM] Launching request-processing task on CPU 2
> > [SVSM] Launching request-processing task on CPU 0
> > [SVSM] Launching request-processing task on CPU 3
> >
> > and then it seems to hang forever.
> > Is that expected? Do I need a specific commit of SVSM or EDK2?
>
> I managed to track down the issue to an infinite loop within KVM. Please
> try the following fix:
>
>     https://github.com/coconut-svsm/linux/pull/19
>
> In my environment this allows edk2 to make progress and reach the grub
> menu. As mentioned in a previous email, you will need to revert
> 539624271cb8 ("sev: require the debug register virtualization feature")
> temporarily in the SVSM.

Finally got around to try your PR. I am able to boot a Fedora 43 guest
through grub
into Linux, but it then hangs early:

[...]
[    0.000000] Linux version 6.17.1-300.fc43.x86_64
(mockbuild@5381c258a4b3436489a448ea66bda8ce) (gcc (GCC) 15.2.1
20250924 (Red Hat 15.2.1-2), GNU ld version 2.45-1.fc43) #1 SMP
PREEMPT_DYNAMIC Mon Oct  6 15:37:21 UTC 2025
[    0.000000] Command line:
BOOT_IMAGE=(hd0,gpt3)/vmlinuz-6.17.1-300.fc43.x86_64 no_timer_check
console=tty1 console=ttyS0,115200n8 systemd.firstboot=off
root=UUID=55773572-92c8-4d7e-bafd-3f4943a2f380 rootflags=subvol=root
[...]
[    1.650687] printk: legacy console [tty1] enabled
[1.651019] printk: legacy console [ttyS0] enabled
[    2.039270] ACPI: Core revision 20250404
[    2.079399] clocksource: hpet: mask: 0xffffffff max_cycles:
0xffffffff, max_idle_ns: 19112604467 ns
[    2.086852] APIC: Switch to symmetric I/O mode setup
[    2.088986] x2apic enabled
[    2.090394] APIC: Switched APIC routing to: physical x2apic
[    2.111585] ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
[    2.113704] clocksource: tsc-
<hangs>

I added in https://github.com/coconut-svsm/linux/pull/18, same result.
Any ideas on what else to try?

Thanks!
 Oliver
>
> Best,
> Carlos
>