KVM: x86: Raise the hard VCPU count limit

The patch raises the hard limit of VCPU count to 254.

This will allow developers to easily work on scalability
and will allow users to test high VCPU setups easily without
patching the kernel.

To prevent possible issues with current setups, KVM_CAP_NR_VCPUS
now returns the recommended VCPU limit (which is still 64) - this
should be a safe value for everybody, while a new KVM_CAP_MAX_VCPUS
returns the hard limit which is now 254.

Cc: Avi Kivity <avi@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Suggested-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index aace6b8691a2..206979877888 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -463,7 +463,7 @@ struct kvm_ppc_pvinfo {
 #define KVM_CAP_VAPIC 6
 #define KVM_CAP_EXT_CPUID 7
 #define KVM_CAP_CLOCKSOURCE 8
-#define KVM_CAP_NR_VCPUS 9       /* returns max vcpus per vm */
+#define KVM_CAP_NR_VCPUS 9       /* returns recommended max vcpus per vm */
 #define KVM_CAP_NR_MEMSLOTS 10   /* returns max memory slots per vm */
 #define KVM_CAP_PIT 11
 #define KVM_CAP_NOP_IO_DELAY 12
@@ -553,6 +553,7 @@ struct kvm_ppc_pvinfo {
 #define KVM_CAP_SPAPR_TCE 63
 #define KVM_CAP_PPC_SMT 64
 #define KVM_CAP_PPC_RMA 65
+#define KVM_CAP_MAX_VCPUS 66       /* returns max vcpus per vm */
 #define KVM_CAP_S390_GMAP 71
 
 #ifdef KVM_CAP_IRQ_ROUTING