[PATCH 1/1] kvm-s390: Provide guest TOD Clock Get/Set Controls

["Jason J. Herne" <jjherne@xxxxxxxxxxxxxxxxxx>]

From: "Jason J. Herne" <jjherne@xxxxxxxxxxxxxxxxxx>

Enable KVM_SET_CLOCK and KVM_GET_CLOCK ioctls on s390 for managing guest Time
Of Day clock value.

Signed-off-by: Jason J. Herne <jjherne@xxxxxxxxxxxxxxxxxx>
Reviewed-by: David Hildenbrand <dahi@xxxxxxxxxxxxxxxxxx>
---
 Documentation/virtual/kvm/api.txt |  4 +--
 arch/s390/kvm/kvm-s390.c          | 74 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+), 2 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 7610eaa..f7eb604 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -745,7 +745,7 @@ struct kvm_xen_hvm_config {
 4.29 KVM_GET_CLOCK
 
 Capability: KVM_CAP_ADJUST_CLOCK
-Architectures: x86
+Architectures: x86, s390
 Type: vm ioctl
 Parameters: struct kvm_clock_data (out)
 Returns: 0 on success, -1 on error
@@ -764,7 +764,7 @@ struct kvm_clock_data {
 4.30 KVM_SET_CLOCK
 
 Capability: KVM_CAP_ADJUST_CLOCK
-Architectures: x86
+Architectures: x86, s390
 Type: vm ioctl
 Parameters: struct kvm_clock_data (in)
 Returns: 0 on success, -1 on error
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 55aade4..774a2a6 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -31,6 +31,7 @@
 #include <asm/switch_to.h>
 #include <asm/facility.h>
 #include <asm/sclp.h>
+#include<asm/timex.h>
 #include "kvm-s390.h"
 #include "gaccess.h"
 
@@ -159,6 +160,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_S390_IRQCHIP:
 	case KVM_CAP_VM_ATTRIBUTES:
 	case KVM_CAP_MP_STATE:
+	case KVM_CAP_ADJUST_CLOCK:
 		r = 1;
 		break;
 	case KVM_CAP_NR_VCPUS:
@@ -328,6 +330,56 @@ static int kvm_s390_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
 	return ret;
 }
 
+static int kvm_s390_get_guest_tod(struct kvm *kvm,
+				  struct kvm_clock_data *user_clock)
+{
+	u64 current_host_tod;
+	u64 epoch = 0;
+	struct kvm_vcpu *vcpu;
+	unsigned int vcpu_idx;
+	int r;
+
+	/* All vcpu's epochs are in sync. Just Grab the 1st one */
+	kvm_for_each_vcpu(vcpu_idx, vcpu, kvm) {
+		epoch = vcpu->arch.sie_block->epoch;
+		break;
+	}
+
+	r = store_tod_clock(&current_host_tod);
+	if (r)
+		return r;
+
+	user_clock->clock = current_host_tod + epoch;
+	return 0;
+}
+
+/*
+Set the guest's effective TOD clock to the given value. The guest's
+TOD clock is determined by the following formula: gtod = host_tod + epoch.
+NOTE: Even though the epoch value is associated with a vcpu, there is only
+one TOD clock and epoch value per guest.  All vcpu's epoch values must be kept
+synchronized.
+*/
+static int kvm_s390_set_guest_tod(struct kvm *kvm,
+				  struct kvm_clock_data *user_clock)
+{
+	u64 current_host_tod, epoch;
+	struct kvm_vcpu *vcpu;
+	unsigned int vcpu_idx;
+	int r;
+
+	r = store_tod_clock(&current_host_tod);
+	if (r)
+		return r;
+
+	epoch = user_clock->clock - current_host_tod;
+
+	kvm_for_each_vcpu(vcpu_idx, vcpu, kvm)
+		vcpu->arch.sie_block->epoch = epoch;
+
+	return 0;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
@@ -387,6 +439,28 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		r = kvm_s390_vm_has_attr(kvm, &attr);
 		break;
 	}
+	case KVM_GET_CLOCK: {
+		struct kvm_clock_data user_clock;
+
+		r = kvm_s390_get_guest_tod(kvm, &user_clock);
+		if (r)
+			break;
+
+		if (copy_to_user(argp, &user_clock, sizeof(user_clock)))
+			r = -EFAULT;
+
+		break;
+	}
+	case KVM_SET_CLOCK: {
+		struct kvm_clock_data user_clock;
+
+		r = -EFAULT;
+		if (copy_from_user(&user_clock, argp,
+				   sizeof(struct kvm_clock_data)))
+			break;
+		r = kvm_s390_set_guest_tod(kvm, &user_clock);
+		break;
+	}
 	default:
 		r = -ENOTTY;
 	}
-- 
1.8.3.2

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