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2023-12-11 d2ccde1c8e90d38cee87a1b0309ad2827f3fd30d 
 kernel/arch/x86/kernel/kvmclock.c
....@@ -1,19 +1,6 @@
1
+// SPDX-License-Identifier: GPL-2.0-or-later
12 /*  KVM paravirtual clock driver. A clocksource implementation
23     Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
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-
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-    This program is free software; you can redistribute it and/or modify
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-    it under the terms of the GNU General Public License as published by
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-    the Free Software Foundation; either version 2 of the License, or
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-    (at your option) any later version.
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-
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-    This program is distributed in the hope that it will be useful,
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-    but WITHOUT ANY WARRANTY; without even the implied warranty of
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-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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-    GNU General Public License for more details.
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-
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-    You should have received a copy of the GNU General Public License
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-    along with this program; if not, write to the Free Software
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-    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
174 */
185 
196 #include <linux/clocksource.h>
....@@ -33,7 +20,6 @@
3320 #include <asm/hypervisor.h>
3421 #include <asm/mem_encrypt.h>
3522 #include <asm/x86_init.h>
36
-#include <asm/reboot.h>
3723 #include <asm/kvmclock.h>
3824 
3925 static int kvmclock __initdata = 1;
....@@ -111,7 +97,7 @@
11197 	if (!stable)
11298 		clear_sched_clock_stable();
11399 	kvm_sched_clock_offset = kvm_clock_read();
114
-	pv_time_ops.sched_clock = kvm_sched_clock_read;
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+	pv_ops.time.sched_clock = kvm_sched_clock_read;
115101 
116102 	pr_info("kvm-clock: using sched offset of %llu cycles",
117103 		kvm_sched_clock_offset);
....@@ -163,12 +149,19 @@
163149 	return ret;
164150 }
165151 
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+static int kvm_cs_enable(struct clocksource *cs)
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+{
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+	vclocks_set_used(VDSO_CLOCKMODE_PVCLOCK);
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+	return 0;
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+}
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+
166158 struct clocksource kvm_clock = {
167159 	.name	= "kvm-clock",
168160 	.read	= kvm_clock_get_cycles,
169161 	.rating	= 400,
170162 	.mask	= CLOCKSOURCE_MASK(64),
171163 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
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+	.enable	= kvm_cs_enable,
172165 };
173166 EXPORT_SYMBOL_GPL(kvm_clock);
174167 
....@@ -201,28 +194,9 @@
201194 }
202195 #endif
203196 
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-/*
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- * After the clock is registered, the host will keep writing to the
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- * registered memory location. If the guest happens to shutdown, this memory
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- * won't be valid. In cases like kexec, in which you install a new kernel, this
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- * means a random memory location will be kept being written. So before any
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- * kind of shutdown from our side, we unregister the clock by writing anything
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- * that does not have the 'enable' bit set in the msr
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- */
212
-#ifdef CONFIG_KEXEC_CORE
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-static void kvm_crash_shutdown(struct pt_regs *regs)
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+void kvmclock_disable(void)
214198 {
215199 	native_write_msr(msr_kvm_system_time, 0, 0);
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-	kvm_disable_steal_time();
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-	native_machine_crash_shutdown(regs);
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-}
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-#endif
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-
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-static void kvm_shutdown(void)
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-{
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-	native_write_msr(msr_kvm_system_time, 0, 0);
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-	kvm_disable_steal_time();
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-	native_machine_shutdown();
226200 }
227201 
228202 static void __init kvmclock_init_mem(void)
....@@ -266,20 +240,19 @@
266240 
267241 static int __init kvm_setup_vsyscall_timeinfo(void)
268242 {
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-#ifdef CONFIG_X86_64
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-	u8 flags;
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-
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-	if (!per_cpu(hv_clock_per_cpu, 0) || !kvmclock_vsyscall)
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-		return 0;
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-
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-	flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
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-	if (!(flags & PVCLOCK_TSC_STABLE_BIT))
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-		return 0;
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-
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-	kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
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-#endif
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-
282243 	kvmclock_init_mem();
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+
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+#ifdef CONFIG_X86_64
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+	if (per_cpu(hv_clock_per_cpu, 0) && kvmclock_vsyscall) {
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+		u8 flags;
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+
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+		flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
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+		if (!(flags & PVCLOCK_TSC_STABLE_BIT))
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+			return 0;
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+
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+		kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK;
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+	}
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+#endif
283256 
284257 	return 0;
285258 }
....@@ -350,11 +323,21 @@
350323 #endif
351324 	x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
352325 	x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
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-	machine_ops.shutdown  = kvm_shutdown;
354
-#ifdef CONFIG_KEXEC_CORE
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-	machine_ops.crash_shutdown  = kvm_crash_shutdown;
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-#endif
357326 	kvm_get_preset_lpj();
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+
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+	/*
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+	 * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate
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+	 * with P/T states and does not stop in deep C-states.
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+	 *
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+	 * Invariant TSC exposed by host means kvmclock is not necessary:
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+	 * can use TSC as clocksource.
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+	 *
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+	 */
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+	if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
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+	    boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
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+	    !check_tsc_unstable())
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+		kvm_clock.rating = 299;
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+
358341 	clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
359342 	pv_info.name = "KVM";
360343 }