From f10a570b093e60c6bd3f210ae909f014f421352a Mon Sep 17 00:00:00 2001 From: Kyle Meyer Date: Thu, 24 Aug 2023 16:52:46 -0500 Subject: KVM: x86: Add CONFIG_KVM_MAX_NR_VCPUS to allow up to 4096 vCPUs Add a Kconfig entry to set the maximum number of vCPUs per KVM guest and set the default value to 4096 when MAXSMP is enabled, as there are use cases that want to create more than the currently allowed 1024 vCPUs and are more than happy to eat the memory overhead. The Hyper-V TLFS doesn't allow more than 64 sparse banks, i.e. allows a maximum of 4096 virtual CPUs. Cap KVM's maximum number of virtual CPUs to 4096 to avoid exceeding Hyper-V's limit as KVM support for Hyper-V is unconditional, and alternatives like dynamically disabling Hyper-V enlightenments that rely on sparse banks would require non-trivial code changes. Suggested-by: Sean Christopherson Signed-off-by: Kyle Meyer Link: https://lore.kernel.org/r/20230824215244.3897419-1-kyle.meyer@hpe.com [sean: massage changelog with --verbose, document #ifdef mess] Signed-off-by: Sean Christopherson --- arch/x86/kvm/Kconfig | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'arch/x86/kvm/Kconfig') diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index ed90f148140d..950c12868d30 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -154,4 +154,15 @@ config KVM_PROVE_MMU config KVM_EXTERNAL_WRITE_TRACKING bool +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. + endif # VIRTUALIZATION -- cgit v1.2.3