KVM: Per-vcpu inodes

Allocate a distinct inode for every vcpu in a VM.  This has the following
benefits:

 - the filp cachelines are no longer bounced when f_count is incremented on
   every ioctl()
 - the API and internal code are distinctly clearer; for example, on the
   KVM_GET_REGS ioctl, there is no need to copy the vcpu number from
   userspace and then copy the registers back; the vcpu identity is derived
   from the fd used to make the call

Right now the performance benefits are completely theoretical since (a) we
don't support more than one vcpu per VM and (b) virtualization hardware
inefficiencies completely everwhelm any cacheline bouncing effects.  But
both of these will change, and we need to prepare the API today.

Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c
index 5a200c0b4b4..3d8ea7ac2ec 100644
--- a/drivers/kvm/svm.c
+++ b/drivers/kvm/svm.c
@@ -600,10 +600,9 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu)
         kfree(vcpu->svm);
 }
 
-static struct kvm_vcpu *svm_vcpu_load(struct kvm_vcpu *vcpu)
+static void svm_vcpu_load(struct kvm_vcpu *vcpu)
 {
         get_cpu();
-        return vcpu;
 }
 
 static void svm_vcpu_put(struct kvm_vcpu *vcpu)