Error : virHostCPUGetKVMMaxVCPUs:1228 : KVM is not supported on this platform: Function not implemented.

[Mario Marietto]

So. ok. If I understood correctly : In my system the file kvm.h is missing.
I should install the kernel headers file if I want it. I could do this if
the kernel in use was 6.1,but I'm forced to use 5.4. I can't install the
kernel headers for the kernel 5.4 on top of debian bookworm. Or at least,at
the moment I don't know how to do this. I'm not sure that the kernel
headers for the 5.4 kernel are present between the packages. Or maybe I can
build it from scratch or I can find it somewhere ? Even in this case, I'm
not sure that they will work on a system that has been compiled on top of a
6.x kernel. I think that I should re-compile libvirt and QEMU on top of the
5.4 kernel and for this reason I should use an older version of
Debian,maybe 8 or 9. Maybe later,I can upgrade the userland from 8/9 to
12,keeping intact the same kernel. What do you think ? Do you see a shorter
solution ? for sure I don't like to reinstall and recompile everything on
an older version of Linux.

On Wed, Aug 30, 2023 at 11:19 AM Mario Marietto <marietto2008 at gmail.com>
wrote:

> ok. I've copied this file :
>
> /home/marietto/Desktop/Dati/virt/qemu-v5.1.0/linux-headers/linux/kvm.h
>
> to this directory :
>
> /usr/include/linux
>
> the previous error is gone,but it still doesn't work :
>
> # virsh domcapabilities --machine virt --emulatorbin
> /usr/local/bin/qemu-system-arm
> error: failed to get emulator capabilities
> error: KVM is not supported on this platform: Function not implemented
>
>
> this time there isn't any specific error :(
>
> On Wed, Aug 30, 2023 at 11:11 AM Mario Marietto <marietto2008 at gmail.com>
> wrote:
>
>> 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 at 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 at 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
>>> --
>>> |: https://berrange.com      -o-
>>> https://www.flickr.com/photos/dberrange :|
>>> |: https://libvirt.org         -o-
>>> https://fstop138.berrange.com :|
>>> |: https://entangle-photo.org    -o-
>>> https://www.instagram.com/dberrange :|
>>>
>>>
>>
>> --
>> Mario.
>>
>
>
> --
> Mario.
>


-- 
Mario.
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