linux-kernel - Re: kconfig does not accept a lower value for KVM_MAX_NR

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Message-ID: <Z42Q-sbPMA9zZMIC@archie.me>
Date: Mon, 20 Jan 2025 06:55:38 +0700
From: Bagas Sanjaya <bagasdotme@...il.com>
To: Toralf Förster <toralf.foerster@....de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux KVM <kvm@...r.kernel.org>
Cc: Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: kconfig does not accept a lower value for KVM_MAX_NR_VCPUS

On Sun, Jan 19, 2025 at 12:04:04PM +0100, Toralf Förster wrote:
> I was wondering why I cannot put a lower value here during make oldconfig:
> 
> 
>   Maximum number of vCPUs per KVM guest (KVM_MAX_NR_VCPUS) [1024] (NEW) 16
>   Maximum number of vCPUs per KVM guest (KVM_MAX_NR_VCPUS) [1024] (NEW) 8
>   Maximum number of vCPUs per KVM guest (KVM_MAX_NR_VCPUS) [1024] (NEW)
> 

Hi Toralf,

From arch/x86/kvm/Kconfig:

>config KVM_MAX_NR_VCPUS
>	int "Maximum number of vCPUs per KVM guest"
>	depends on KVM
>	range 1024 4096
>	default 4096 if MAXSMP
>	default 1024
>	help
>	  Set the maximum number of vCPUs per KVM guest. Larger values will increase
>	  the memory footprint of each KVM guest, regardless of how many vCPUs are
>	  created for a given VM.

I don't know your use case, but you can safely choose the default (1024).

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

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