Ok. thanks. Yes,I'm obliged to use a kernel minor than 5.7 and I've chosen 5.4. These are the places where I've found the kvm.h file that I need.

/home/marietto/Desktop/Dati/virt/qemu-v5.1.0/include/sysemu/kvm.h

/home/marietto/Desktop/Dati/virt/qemu-v5.1.0/linux-headers/asm-arm/kvm.h

/home/marietto/Desktop/Dati/virt/qemu-v5.1.0/linux-headers/linux/kvm.h

/home/marietto/Desktop/Dati/200/Si/linux-5.4.244/tools/include/uapi/linux/kvm.h
/home/marietto/Desktop/Dati/200/Si/linux-5.4.244/tools/arch/arm/include/uapi/asm/kvm.h
/home/marietto/Desktop/Dati/200/Si/linux-5.4.244/include/uapi/linux/kvm.h
/home/marietto/Desktop/Dati/200/Si/linux-5.4.244/include/config/kvm.h
/home/marietto/Desktop/Dati/200/Si/linux-5.4.244/include/trace/events/kvm.h
/home/marietto/Desktop/Dati/200/Si/linux-5.4.244/arch/arm/include/uapi/asm/kvm.h

Basically it seems that I can get it from the qemu 5.1 or from the kernel 5.4 source code files. Can you tell me what's the correct one ? You talked about linux-headers,so it might be this :

/home/marietto/Desktop/Dati/virt/qemu-v5.1.0/linux-headers/linux/kvm.h

?

where should I copy it ? to /usr/include/linux is the right place ?

thanks.

On Wed, Aug 30, 2023 at 9:46 AM Daniel P. Berrangé <berrange@redhat.com> wrote:

On Tue, Aug 29, 2023 at 09:22:35PM +0200, Mario Marietto wrote:
> Hello.
>
> I'm running Debian bookworm on my ARM Chromebook,model "xe303c12" and
> I've recompiled the kernel (5.4) to enable KVM,so now my system sounds like
> this :

That's surely not the default kernel that comes with Debian bookworm,
as that 5.4 version is many years old.

IIUC the standard bookworm kernel will be 6.4

> root@chromarietto:~#  virsh domcapabilities --machine virt
> --emulatorbin /usr/local/bin/qemu-system-arm
>
> 2023-08-29 10:17:59.110+0000: 1763: error : virHostCPUGetKVMMaxVCPUs:1228 :
> KVM is not supported on this platform: Function not implemented ;
> error: failed to get emulator capabilities
> error: KVM is not supported on this platform: Function not implemented

This shows libvirt was built against a kernel that lacks the
kvm.h header file.

This is expected for armv7 as support for KVM on 32-bit arm was
deleted in the 5.7 kernel. I expect libvirt was built against
the kernel headers from Debian's default 6.4 kernel and thus
lacks KVM support.

Your booting of the old 5.4 kernel doesn't solve this - you
would actually need to build libvirt (and QEMU) against this
outdated kernel too.


With regards,
Daniel
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Mario.