KVM: Allow userspace to process hypercalls which have no kernel handler

This is useful for paravirtualized graphics devices, for example.

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

2 files changed, 26 insertions, 2 deletions

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 39cf8fd343a3..de93117f1e97 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -1203,7 +1203,16 @@ int kvm_hypercall(struct kvm_vcpu *vcpu, struct kvm_run *run)
         }
         switch (nr) {
         default:
-                ;
+                run->hypercall.args[0] = a0;
+                run->hypercall.args[1] = a1;
+                run->hypercall.args[2] = a2;
+                run->hypercall.args[3] = a3;
+                run->hypercall.args[4] = a4;
+                run->hypercall.args[5] = a5;
+                run->hypercall.ret = ret;
+                run->hypercall.longmode = is_long_mode(vcpu);
+                kvm_arch_ops->decache_regs(vcpu);
+                return 0;
         }
         vcpu->regs[VCPU_REGS_RAX] = ret;
         kvm_arch_ops->decache_regs(vcpu);
@@ -1599,6 +1608,13 @@ static int kvm_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 
         vcpu->mmio_needed = 0;
 
+        if (kvm_run->exit_type == KVM_EXIT_TYPE_VM_EXIT
+            && kvm_run->exit_reason == KVM_EXIT_HYPERCALL) {
+                kvm_arch_ops->cache_regs(vcpu);
+                vcpu->regs[VCPU_REGS_RAX] = kvm_run->hypercall.ret;
+                kvm_arch_ops->decache_regs(vcpu);
+        }
+
         r = kvm_arch_ops->run(vcpu, kvm_run);
 
         vcpu_put(vcpu);
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index c93cf53953af..9151ebfa22e9 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -11,7 +11,7 @@
 #include <asm/types.h>
 #include <linux/ioctl.h>
 
-#define KVM_API_VERSION 6
+#define KVM_API_VERSION 7
 
 /*
  * Architectural interrupt line count, and the size of the bitmap needed
@@ -41,6 +41,7 @@ enum kvm_exit_reason {
         KVM_EXIT_UNKNOWN          = 0,
         KVM_EXIT_EXCEPTION        = 1,
         KVM_EXIT_IO               = 2,
+        KVM_EXIT_HYPERCALL        = 3,
         KVM_EXIT_DEBUG            = 4,
         KVM_EXIT_HLT              = 5,
         KVM_EXIT_MMIO             = 6,
@@ -103,6 +104,13 @@ struct kvm_run {
                         __u32 len;
                         __u8  is_write;
                 } mmio;
+                /* KVM_EXIT_HYPERCALL */
+                struct {
+                        __u64 args[6];
+                        __u64 ret;
+                        __u32 longmode;
+                        __u32 pad;
+                } hypercall;
         };
 };