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/vmx.c b/drivers/kvm/vmx.c
index ff956a6302ec..c07178e61122 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -204,7 +204,7 @@ static void vmcs_write64(unsigned long field, u64 value)
  * Switches to specified vcpu, until a matching vcpu_put(), but assumes
  * vcpu mutex is already taken.
  */
-static struct kvm_vcpu *vmx_vcpu_load(struct kvm_vcpu *vcpu)
+static void vmx_vcpu_load(struct kvm_vcpu *vcpu)
 {
         u64 phys_addr = __pa(vcpu->vmcs);
         int cpu;
@@ -242,7 +242,6 @@ static struct kvm_vcpu *vmx_vcpu_load(struct kvm_vcpu *vcpu)
                 rdmsrl(MSR_IA32_SYSENTER_ESP, sysenter_esp);
                 vmcs_writel(HOST_IA32_SYSENTER_ESP, sysenter_esp); /* 22.2.3 */
         }
-        return vcpu;
 }
 
 static void vmx_vcpu_put(struct kvm_vcpu *vcpu)