drivers: hv: mshv_vtl: Implement restore partition time IOCTL

arch/x86/include/asm/mshyperv.h

@@ -241,6 +241,8 @@ void hyperv_setup_mmu_ops(void);
 void set_hv_tscchange_cb(void (*cb)(void));
 void clear_hv_tscchange_cb(void);
 void hyperv_stop_tsc_emulation(void);
+void hv_save_sched_clock_state(void);
+void hv_restore_sched_clock_state(void);
 int hyperv_flush_guest_mapping(u64 as);
 int hyperv_flush_guest_mapping_range(u64 as,
 		hyperv_fill_flush_list_func fill_func, void *data);

arch/x86/kernel/cpu/mshyperv.c

@@ -266,13 +266,13 @@ static void restore_hv_clock_tsc_state(void)
  * suspend-resume and the offset used to measure time needs to be
  * corrected, post resume.
  */
-static void hv_save_sched_clock_state(void)
+void hv_save_sched_clock_state(void)
 {
 	old_save_sched_clock_state();
 	save_hv_clock_tsc_state();
 }
 
-static void hv_restore_sched_clock_state(void)
+void hv_restore_sched_clock_state(void)
 {
 	restore_hv_clock_tsc_state();
 	old_restore_sched_clock_state();

drivers/hv/mshv_vtl_main.c

@@ -32,6 +32,7 @@
 
 #ifdef CONFIG_X86_64
 #include <linux/cleanup.h>
+#include <linux/stop_machine.h>
 
 #include <asm/apic.h>
 #include <uapi/asm/mtrr.h>
@@ -42,6 +43,7 @@
 #include <asm/vmx.h>
 
 #include "../../kernel/fpu/legacy.h"
+#include "../../kernel/time/timekeeping.h"
 
 #endif
 
@@ -865,6 +867,55 @@ static int mshv_vtl_ioctl_add_vtl0_mem(struct mshv_vtl *vtl, void __user *arg)
 	return 0;
 }
 
+#ifdef CONFIG_X86_64
+static int restore_partition_time_with_cpus_stopped(void *data)
+{
+	struct mshv_partition_time *partition_time = data;
+	struct hv_input_restore_partition_time *input;
+	int result = 0;
+	u64 status;
+
+	/* Save current clock state. Other CPUs are waiting in stop code, so no locks are taken. */
+	sched_clock_suspend();
+	timekeeping_suspend();
+	hv_save_sched_clock_state();
+
+	/* Interrupts are disabled. Make the hypercall to update the TSC. */
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	input->partition_id = HV_PARTITION_ID_SELF;
+	input->tsc_sequence = partition_time->tsc_sequence;
+	input->reserved = 0;
+	input->reference_time_in_100_ns = partition_time->reference_time_in_100_ns;
+	input->tsc = partition_time->tsc;
+	status = hv_do_hypercall(HVCALL_RESTORE_PARTITION_TIME, input, NULL);
+	if (!hv_result_success(status)) {
+		pr_err("HVCALL_RESTORE_PARTITION_TIME failed with %#llx\n", status);
+		result = -EINVAL;
+	}
+
+	/* Restore clock state using current TSC value. */
+	hv_restore_sched_clock_state();
+	timekeeping_resume();
+	sched_clock_resume();
+
+	return result;
+}
+
+static int mshv_restore_partition_time(void __user *arg)
+{
+	struct mshv_partition_time partition_time;
+	int ret;
+
+	if (copy_from_user(&partition_time, arg, sizeof(partition_time)))
+		return -EFAULT;
+
+	/* Stop other CPUs, using the current one to restore partition time. */
+	ret = stop_machine(restore_partition_time_with_cpus_stopped, &partition_time,
+			cpumask_of(raw_smp_processor_id()));
+	return ret;
+}
+#endif
+
 static void mshv_vtl_cancel(int cpu)
 {
 	int here = get_cpu();
@@ -2596,6 +2647,13 @@ mshv_vtl_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 	case MSHV_VTL_ADD_VTL0_MEMORY:
 		ret = mshv_vtl_ioctl_add_vtl0_mem(vtl, (void __user *)arg);
 		break;
+
+#if defined(CONFIG_X86_64)
+	case MSHV_RESTORE_PARTITION_TIME:
+		ret = mshv_restore_partition_time((void __user *)arg);
+		break;
+#endif
+
 #if defined(CONFIG_X86_64) && defined(CONFIG_INTEL_TDX_GUEST)
 	case MSHV_VTL_TDCALL:
 		ret = mshv_vtl_ioctl_tdcall((void __user *)arg);

include/uapi/hyperv/hvgdk_mini.h

@@ -261,6 +261,8 @@ union hv_hypervisor_version_info {
 #define HVCALL_GET_VP_CPUID_VALUES		0x00f4
 #define HVCALL_START_VP				0x0099
 #define HVCALL_GET_VP_INDEX_FROM_APIC_ID		0x009a
+#define HVCALL_RESTORE_PARTITION_TIME		0x0103
+
 
 /*
  * Some macros - i.e. GENMASK_ULL and BIT_ULL - are not currently supported by
@@ -1310,4 +1312,14 @@ struct hv_input_install_intercept {
 	union hv_intercept_parameters intercept_parameter;
 } __packed;
 
+#if defined(__x86_64__)
+struct hv_input_restore_partition_time {
+	__u64 partition_id;
+	__u32 tsc_sequence;
+	__u32 reserved;
+	__u64 reference_time_in_100_ns;
+	__u64 tsc;
+} __packed;
+#endif
+
 #endif /* _UAPI_HV_HVGDK_MINI_H */

include/uapi/linux/mshv.h

@@ -306,6 +306,13 @@ struct mshv_map_device_intr {
 	__u8 padding[7];
 } __packed;
 
+struct mshv_partition_time {
+	__u32 tsc_sequence;
+	__u32 reserved;
+	__u64 reference_time_in_100_ns;
+	__u64 tsc;
+} __packed;
+
 #define MSHV_KICK_CPUS_FLAG_WAIT_FOR_CPUS	(1 << 0)
 #define MSHV_KICK_CPUS_FLAG_CANCEL_CPU_RUN	(1 << 1)
 
@@ -371,6 +378,7 @@ struct mshv_map_device_intr {
 						       struct mshv_map_device_intr)
 
 /* For x86-64 only */
+#define MSHV_RESTORE_PARTITION_TIME	_IOW(MSHV_IOCTL, 0x13, struct mshv_partition_time)
 #define MSHV_VTL_GUEST_VSM_VMSA_PFN	_IOWR(MSHV_IOCTL, 0x34, __u64)
 
 /* For x86-64 SEV-SNP only */