[KVM-NYX] Error: IP Payloads are LIP!

[Kristinaa78]

While trying to follow the installation process, kafl fuzz fails with

Intel PT is not supported on this CPU!

error. Permissions to /dev/kvm should be set correctly. In my dmesg output there is BOOT_IMAGE=/boot/vmlinuz-6.0.0-nyx+ but also [KVM-NYX] Error: IP Payloads are LIP! error. I use a fairly new CPU - i5-1335U and Intel PT should be, in fact, supported. Is there any way how can I resolve this?

[Wenzel]

Hi,

can you give me the output of this command line ?

echo -n "Intel PT support: "; if $(grep -q "intel_pt" /proc/cpuinfo); then echo "✅"; else echo "❌"; fi

The error you are seeing is located here:
https://github.com/IntelLabs/kafl.linux/blob/kvm-nyx-6.0/arch/x86/kvm/vmx/vmx_pt.c#L1119

@schumilo can you shed some lights on this LIP Intel PT feature ?
What does it refer to ?
I found some reference to Linear Instruction Pointer, but not a PT expert.

[Kristinaa78]

Yes, sure. It says it's enabled:

I have also traced the error message down to the very line you posted but have no idea how to proceed.

[Kristinaa78]

Update: I have tried to disable E-cores in BIOS and no error occurs. dmesg reports that CPU is supported! and kafl fuzz does not fail anymore. However, performance decrease might make it unusable.

[Wenzel]

Thanks for sharing that result here, I'll keep a note 🗒️ !
Happy fuzzing !