On Mon, Jan 20, 2025, Bagas Sanjaya wrote: > 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: The lower limit of 1024 in the Kconfig exists to ensure backwards compatibility. CONFIG_KVM_MAX_NR_VCPUS is effectively exposed to userspace via KVM_CAP_MAX_VCPUS, and prior to the Kconfig KVM hardcoded KVM_CAP_MAX_VCPUS to 1024. I did float the idea of setting the range to 1 - 4096, but we opted to go with the conservative approach because the benefits are relatively minor, and we didn't want to risk indirectly breaking userspace. > > 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
