KVM: add MSR based hypercall API

This adds a special MSR based hypercall API to KVM. This is to be
used by paravirtual kernels and virtual drivers.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index d1198e2b2b5d..0198d400037f 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -1469,6 +1469,18 @@ static int handle_io(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         return 0;
 }
 
+static void
+vmx_patch_hypercall(struct kvm_vcpu *vcpu, unsigned char *hypercall)
+{
+        /*
+         * Patch in the VMCALL instruction:
+         */
+        hypercall[0] = 0x0f;
+        hypercall[1] = 0x01;
+        hypercall[2] = 0xc1;
+        hypercall[3] = 0xc3;
+}
+
 static int handle_cr(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 {
         u64 exit_qualification;
@@ -2064,6 +2076,7 @@ static struct kvm_arch_ops vmx_arch_ops = {
         .run = vmx_vcpu_run,
         .skip_emulated_instruction = skip_emulated_instruction,
         .vcpu_setup = vmx_vcpu_setup,
+        .patch_hypercall = vmx_patch_hypercall,
 };
 
 static int __init vmx_init(void)