On Sat, Mar 25, 2023 at 08:13:26PM +0200, Zhi Wang <zhi.wang.linux@xxxxxxxxx> wrote: > On Sun, 12 Mar 2023 10:55:42 -0700 > isaku.yamahata@xxxxxxxxx wrote: > > > From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > > > > TDX has its own limitation on the maximum number of vcpus that the guest > > can accommodate. Allow x86 kvm backend to implement its own KVM_ENABLE_CAP > > handler and implement TDX backend for KVM_CAP_MAX_VCPUS. user space VMM, > > e.g. qemu, can specify its value instead of KVM_MAX_VCPUS. > > > > I think enabling the cap here is actually "configuring the cap". KVM_CAP_MAX > _VCPUS is actually always enabled whether userspace enables it or not. It > would be nice to configure of the max VCPUS in kvm_arch_vm_ioctl() where > routines of configuring a VM should belong. E.g. KVM_SET_MAX_VCPUS. I'm not sure I understand your point. Although KVM_ENABLE_CAP sounds like only on/off feature, but it isn't. It's also used to set parameters. For example, KVM_CAP_MAX_VCPU_ID. KVM_SET_XXX is for run time feature. But the maxium number of vcpus is not runtime changable. Set it at vm creation. -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
