[PATCH 2/3] KVM: x86: Extract __kvm_set_clock() from kvm_vm_ioctl_set_clock()

[Mushahid Hussain <hmushi@amazon.co.uk>]

Move the body of KVM_SET_CLOCK into __kvm_set_clock() and leave the
copy from userspace and the flags check in the ioctl handler. A
following patch steps kvmclock from inside KVM and needs the worker.

No functional change intended.

Assisted-by: Claude:claude-fable-5.1
Signed-off-by: Mushahid Hussain <hmushi@amazon.co.uk>
---
 arch/x86/kvm/x86.c | 40 +++++++++++++++++++++++-----------------
 1 file changed, 23 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 32563a91fba99..19666a80240a5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4354,22 +4354,11 @@ static int kvm_vm_ioctl_get_clock(struct kvm *kvm, void __user *argp)
 	return 0;
 }
 
-static int kvm_vm_ioctl_set_clock(struct kvm *kvm, void __user *argp)
+static void __kvm_set_clock(struct kvm *kvm, struct kvm_clock_data *data)
 {
 	struct kvm_arch *ka = &kvm->arch;
-	struct kvm_clock_data data;
 	u64 now_raw_ns;
 
-	if (copy_from_user(&data, argp, sizeof(data)))
-		return -EFAULT;
-
-	/*
-	 * Only KVM_CLOCK_REALTIME is used, but allow passing the
-	 * result of KVM_GET_CLOCK back to KVM_SET_CLOCK.
-	 */
-	if (data.flags & ~KVM_CLOCK_VALID_FLAGS)
-		return -EINVAL;
-
 	kvm_hv_request_tsc_page_update(kvm);
 	kvm_start_pvclock_update(kvm);
 	pvclock_update_vm_gtod_copy(kvm);
@@ -4379,24 +4368,41 @@ static int kvm_vm_ioctl_set_clock(struct kvm *kvm, void __user *argp)
 	 * in use, we use master_kernel_ns + kvmclock_offset to set
 	 * unsigned 'system_time' so if we use get_kvmclock_ns() (which
 	 * is slightly ahead) here we risk going negative on unsigned
-	 * 'system_time' when 'data.clock' is very small.
+	 * 'system_time' when 'data->clock' is very small.
 	 */
-	if (data.flags & KVM_CLOCK_REALTIME) {
+	if (data->flags & KVM_CLOCK_REALTIME) {
 		u64 now_real_ns = ktime_get_real_ns();
 
 		/*
 		 * Avoid stepping the kvmclock backwards.
 		 */
-		if (now_real_ns > data.realtime)
-			data.clock += now_real_ns - data.realtime;
+		if (now_real_ns > data->realtime)
+			data->clock += now_real_ns - data->realtime;
 	}
 
 	if (ka->use_master_clock)
 		now_raw_ns = ka->master_kernel_ns;
 	else
 		now_raw_ns = get_kvmclock_base_ns();
-	ka->kvmclock_offset = data.clock - now_raw_ns;
+	ka->kvmclock_offset = data->clock - now_raw_ns;
 	kvm_end_pvclock_update(kvm);
+}
+
+static int kvm_vm_ioctl_set_clock(struct kvm *kvm, void __user *argp)
+{
+	struct kvm_clock_data data;
+
+	if (copy_from_user(&data, argp, sizeof(data)))
+		return -EFAULT;
+
+	/*
+	 * Only KVM_CLOCK_REALTIME is used, but allow passing the
+	 * result of KVM_GET_CLOCK back to KVM_SET_CLOCK.
+	 */
+	if (data.flags & ~KVM_CLOCK_VALID_FLAGS)
+		return -EINVAL;
+
+	__kvm_set_clock(kvm, &data);
 	return 0;
 }
 
-- 
2.47.3