> > 4096 is the current maximum value because of the Hyper-V TLFS. See > > BUILD_BUG_ON in arch/x86/kvm/hyperv.c, commit 79661c3, and Vitaly's > > comment on https://lore.kernel.org/all/87r136shcc.fsf@xxxxxxxxxx. > > Mostly out of curiosity, do you care about Hyper-V support? If not, at some > point it'd probably be worth exploring a CONFIG_KVM_HYPERV option to allow > disabling KVM's Hyper-V support at compile time so that we're not bound by the > restrictions of the TLFS. Yes, I care about Hyper-V support. I would like this limitation to be addressed in the future. > Rather than tightly couple this to MAXSMP, what if we add a Kconfig? I know of > at least one scenario, SVM's AVIC/x2AVIC, where it would be desirable to configure > KVM to a much smaller maximum. The biggest downside I can think of is that KVM > selftests would need to be updated (they assume the max is >=512), and some of the > tests might be completely invalid if KVM_MAX_VCPUS is too low (<256?). That sounds good to me. I would prefer to set the range from 1024 to 4096 in this patch.
