On Tue, 03 May 2016 06:52:02 +0200 Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx> wrote: > The KVM_MAX_VCPUS define provides the maximum number of vCPUs per guest, and > also the upper limit for vCPU ids. This is okay for all archs except PowerPC > which can have higher ids, depending on the cpu/core/thread topology. In the > worst case (single threaded guest, host with 8 threads per core), it limits > the maximum number of vCPUS to KVM_MAX_VCPUS / 8. > > This patch separates the vCPU numbering from the total number of vCPUs, with > the introduction of KVM_MAX_VCPU_ID, as the maximal valid value for vCPU ids > plus one. > > The corresponding KVM_CAP_MAX_VCPU_ID allows userspace to validate vCPU ids > before passing them to KVM_CREATE_VCPU. > > Only PowerPC gets unlimited vCPU ids for the moment. This patch doesn't > change anything for other archs. > > Suggested-by: Radim Krcmar <rkrcmar@xxxxxxxxxx> > Signed-off-by: Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx> > --- > Documentation/virtual/kvm/api.txt | 10 ++++++++-- > arch/powerpc/include/asm/kvm_host.h | 2 ++ > arch/powerpc/kvm/powerpc.c | 3 +++ > include/linux/kvm_host.h | 4 ++++ > include/uapi/linux/kvm.h | 1 + > virt/kvm/kvm_main.c | 2 +- > 6 files changed, 19 insertions(+), 3 deletions(-) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 23bfe1bd159c..3b4efa1c088c 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -35,6 +35,10 @@ > > #include <asm/kvm_host.h> > > +#ifndef KVM_MAX_VCPU_ID > +#define KVM_MAX_VCPU_ID KVM_MAX_VCPUS As you are defining KVM_MAX_VCPU_ID in any case, would it make sense to provide the cap in generic code? power will simply override the value. > +#endif > + > /* > * The bit 16 ~ bit 31 of kvm_memory_region::flags are internally used > * in kvm, other bits are visible for userspace which are defined in
