Re: [pve-devel] [PATCH pve-manager] qemu: bump max cores to 256 by socket

["DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>]

>>Is the QEMU error message understandable? If yes, I don't see much
>>value

Well, indeed, the message is pretty clear.
maybe just add documentation about limit for q35 && i440fx ?

(I have a customer with a new epyc v4, asking me about this, and I had
no idea that they was a different limit between q35 && i440fx)



with i440fx (and 512 cores)

# qm start 105
kvm: Invalid SMP CPUs 512. The max CPUs supported by machine 'pc-
i440fx-8.1' is 255


with q35 (and 4096 cores)

# qm start 105
kvm: Invalid SMP CPUs 4096. The max CPUs supported by machine 'pc-q35-
8.1' is 1024


-------- Message initial --------
De: Fiona Ebner <f.ebner@proxmox.com>
À: Proxmox VE development discussion <pve-devel@lists.proxmox.com>,
"DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>,
d.csapak@proxmox.com <d.csapak@proxmox.com>, aderumier@odiso.com
<aderumier@odiso.com>
Objet: Re: [pve-devel] [PATCH pve-manager] qemu: bump max cores to 256
by socket
Date: 15/01/2024 14:08:39

Am 15.01.24 um 13:43 schrieb DERUMIER, Alexandre:
> 
> 
> Maybe an improvement in qemu-server, could be to add additional check
> at vm start, (maybe a simple warn), depending of qemu version or
> setup. 
> For example, 1024 cores only works with q35 && qemu 8.1,
> it could be interesting to give an clean hint  mesage to user instead
> a qemu process error.
> 

Is the QEMU error message understandable? If yes, I don't see much
value
in adding such a heuristic and warning ourselves. If no, we can either
improve the QEMU error message or do as you suggested.