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/svm.c b/drivers/kvm/svm.c
index 72cac0488b31..f6e86528f031 100644
--- a/drivers/kvm/svm.c
+++ b/drivers/kvm/svm.c
@@ -1669,6 +1669,18 @@ static int is_disabled(void)
         return 0;
 }
 
+static void
+svm_patch_hypercall(struct kvm_vcpu *vcpu, unsigned char *hypercall)
+{
+        /*
+         * Patch in the VMMCALL instruction:
+         */
+        hypercall[0] = 0x0f;
+        hypercall[1] = 0x01;
+        hypercall[2] = 0xd9;
+        hypercall[3] = 0xc3;
+}
+
 static struct kvm_arch_ops svm_arch_ops = {
         .cpu_has_kvm_support = has_svm,
         .disabled_by_bios = is_disabled,
@@ -1717,6 +1729,7 @@ static struct kvm_arch_ops svm_arch_ops = {
         .run = svm_vcpu_run,
         .skip_emulated_instruction = skip_emulated_instruction,
         .vcpu_setup = svm_vcpu_setup,
+        .patch_hypercall = svm_patch_hypercall,
 };
 
 static int __init svm_init(void)