v4: allow userspace to adjust kvmclock offset

Commit Message

Glauber Costa Oct. 14, 2009, 2:47 p.m. UTC

None

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 179a919..c9b0d9f 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -410,6 +410,7 @@  struct kvm_arch{
 
 	unsigned long irq_sources_bitmap;
 	u64 vm_init_tsc;
+	s64 kvmclock_offset;
 };
 
 struct kvm_vm_stat {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9601bc6..09f31e2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -699,7 +699,8 @@  static void kvm_write_guest_time(struct kvm_vcpu *v)
 	/* With all the info we got, fill in the values */
 
 	vcpu->hv_clock.system_time = ts.tv_nsec +
-				     (NSEC_PER_SEC * (u64)ts.tv_sec);
+				     (NSEC_PER_SEC * (u64)ts.tv_sec) + v->kvm->arch.kvmclock_offset;
+
 	/*
 	 * The interface expects us to write an even number signaling that the
 	 * update is finished. Since the guest won't see the intermediate
@@ -2441,6 +2442,38 @@  long kvm_arch_vm_ioctl(struct file *filp,
 		r = 0;
 		break;
 	}
+	case KVM_SET_CLOCK: {
+		struct timespec now;
+		struct kvm_clock_data user_ns;
+		u64 now_ns;
+		s64 delta;
+
+		r =  -EFAULT;
+		if (copy_from_user(&user_ns, argp, sizeof(user_ns)))
+			goto out;
+
+		r = 0;
+		ktime_get_ts(&now);
+		now_ns = timespec_to_ns(&now);
+		delta = user_ns.clock - now_ns;
+		kvm->arch.kvmclock_offset = delta;
+		break;	
+	}
+	case KVM_GET_CLOCK: {
+		struct timespec now;
+		struct kvm_clock_data user_ns;
+		u64 now_ns;
+
+		ktime_get_ts(&now);
+		now_ns = timespec_to_ns(&now);
+		user_ns.clock = kvm->arch.kvmclock_offset + now_ns;
+
+		if (copy_to_user(argp, &user_ns, sizeof(user_ns)))
+			r =  -EFAULT;
+
+		break;	
+	}
+
 	default:
 		;
 	}
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index f8f8900..ad0ecbc 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -497,6 +497,11 @@  struct kvm_irqfd {
 	__u8  pad[20];
 };
 
+struct kvm_clock_data {
+	__u64 clock;
+	__u64 pad[2];
+};
+
 /*
  * ioctls for VM fds
  */
@@ -546,6 +551,8 @@  struct kvm_irqfd {
 #define KVM_CREATE_PIT2		   _IOW(KVMIO, 0x77, struct kvm_pit_config)
 #define KVM_SET_BOOT_CPU_ID        _IO(KVMIO, 0x78)
 #define KVM_IOEVENTFD             _IOW(KVMIO, 0x79, struct kvm_ioeventfd)
+#define KVM_SET_CLOCK		  _IOW(KVMIO, 0x7a, struct kvm_clock_data)
+#define KVM_GET_CLOCK		  _IOW(KVMIO, 0x7b, struct kvm_clock_data)
 
 /*
  * ioctls for vcpu fds