1 files changed, 349 insertions, 0 deletions
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
new file mode 100644
index 000000000..c067887d4
--- /dev/null
+++ b/arch/x86/kernel/kvmclock.c
@@ -0,0 +1,349 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*  KVM paravirtual clock driver. A clocksource implementation
+    Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
+*/
+
+#include <linux/clocksource.h>
+#include <linux/kvm_para.h>
+#include <asm/pvclock.h>
+#include <asm/msr.h>
+#include <asm/apic.h>
+#include <linux/percpu.h>
+#include <linux/hardirq.h>
+#include <linux/cpuhotplug.h>
+#include <linux/sched.h>
+#include <linux/sched/clock.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/set_memory.h>
+#include <linux/cc_platform.h>
+
+#include <asm/hypervisor.h>
+#include <asm/x86_init.h>
+#include <asm/kvmclock.h>
+
+static int kvmclock __initdata = 1;
+static int kvmclock_vsyscall __initdata = 1;
+static int msr_kvm_system_time __ro_after_init;
+static int msr_kvm_wall_clock __ro_after_init;
+static u64 kvm_sched_clock_offset __ro_after_init;
+
+static int __init parse_no_kvmclock(char *arg)
+{
+	kvmclock = 0;
+	return 0;
+}
+early_param("no-kvmclock", parse_no_kvmclock);
+
+static int __init parse_no_kvmclock_vsyscall(char *arg)
+{
+	kvmclock_vsyscall = 0;
+	return 0;
+}
+early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
+
+/* Aligned to page sizes to match whats mapped via vsyscalls to userspace */
+#define HVC_BOOT_ARRAY_SIZE \
+	(PAGE_SIZE / sizeof(struct pvclock_vsyscall_time_info))
+
+static struct pvclock_vsyscall_time_info
+			hv_clock_boot[HVC_BOOT_ARRAY_SIZE] __bss_decrypted __aligned(PAGE_SIZE);
+static struct pvclock_wall_clock wall_clock __bss_decrypted;
+static struct pvclock_vsyscall_time_info *hvclock_mem;
+DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu);
+EXPORT_PER_CPU_SYMBOL_GPL(hv_clock_per_cpu);
+
+/*
+ * The wallclock is the time of day when we booted. Since then, some time may
+ * have elapsed since the hypervisor wrote the data. So we try to account for
+ * that with system time
+ */
+static void kvm_get_wallclock(struct timespec64 *now)
+{
+	wrmsrl(msr_kvm_wall_clock, slow_virt_to_phys(&wall_clock));
+	preempt_disable();
+	pvclock_read_wallclock(&wall_clock, this_cpu_pvti(), now);
+	preempt_enable();
+}
+
+static int kvm_set_wallclock(const struct timespec64 *now)
+{
+	return -ENODEV;
+}
+
+static u64 kvm_clock_read(void)
+{
+	u64 ret;
+
+	preempt_disable_notrace();
+	ret = pvclock_clocksource_read(this_cpu_pvti());
+	preempt_enable_notrace();
+	return ret;
+}
+
+static u64 kvm_clock_get_cycles(struct clocksource *cs)
+{
+	return kvm_clock_read();
+}
+
+static u64 kvm_sched_clock_read(void)
+{
+	return kvm_clock_read() - kvm_sched_clock_offset;
+}
+
+static inline void kvm_sched_clock_init(bool stable)
+{
+	if (!stable)
+		clear_sched_clock_stable();
+	kvm_sched_clock_offset = kvm_clock_read();
+	paravirt_set_sched_clock(kvm_sched_clock_read);
+
+	pr_info("kvm-clock: using sched offset of %llu cycles",
+		kvm_sched_clock_offset);
+
+	BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
+		sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
+}
+
+/*
+ * If we don't do that, there is the possibility that the guest
+ * will calibrate under heavy load - thus, getting a lower lpj -
+ * and execute the delays themselves without load. This is wrong,
+ * because no delay loop can finish beforehand.
+ * Any heuristics is subject to fail, because ultimately, a large
+ * poll of guests can be running and trouble each other. So we preset
+ * lpj here
+ */
+static unsigned long kvm_get_tsc_khz(void)
+{
+	setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
+	return pvclock_tsc_khz(this_cpu_pvti());
+}
+
+static void __init kvm_get_preset_lpj(void)
+{
+	unsigned long khz;
+	u64 lpj;
+
+	khz = kvm_get_tsc_khz();
+
+	lpj = ((u64)khz * 1000);
+	do_div(lpj, HZ);
+	preset_lpj = lpj;
+}
+
+bool kvm_check_and_clear_guest_paused(void)
+{
+	struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
+	bool ret = false;
+
+	if (!src)
+		return ret;
+
+	if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) {
+		src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED;
+		pvclock_touch_watchdogs();
+		ret = true;
+	}
+	return ret;
+}
+
+static int kvm_cs_enable(struct clocksource *cs)
+{
+	vclocks_set_used(VDSO_CLOCKMODE_PVCLOCK);
+	return 0;
+}
+
+struct clocksource kvm_clock = {
+	.name	= "kvm-clock",
+	.read	= kvm_clock_get_cycles,
+	.rating	= 400,
+	.mask	= CLOCKSOURCE_MASK(64),
+	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.enable	= kvm_cs_enable,
+};
+EXPORT_SYMBOL_GPL(kvm_clock);
+
+static void kvm_register_clock(char *txt)
+{
+	struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
+	u64 pa;
+
+	if (!src)
+		return;
+
+	pa = slow_virt_to_phys(&src->pvti) | 0x01ULL;
+	wrmsrl(msr_kvm_system_time, pa);
+	pr_debug("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt);
+}
+
+static void kvm_save_sched_clock_state(void)
+{
+}
+
+static void kvm_restore_sched_clock_state(void)
+{
+	kvm_register_clock("primary cpu clock, resume");
+}
+
+#ifdef CONFIG_X86_LOCAL_APIC
+static void kvm_setup_secondary_clock(void)
+{
+	kvm_register_clock("secondary cpu clock");
+}
+#endif
+
+void kvmclock_disable(void)
+{
+	if (msr_kvm_system_time)
+		native_write_msr(msr_kvm_system_time, 0, 0);
+}
+
+static void __init kvmclock_init_mem(void)
+{
+	unsigned long ncpus;
+	unsigned int order;
+	struct page *p;
+	int r;
+
+	if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus())
+		return;
+
+	ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE;
+	order = get_order(ncpus * sizeof(*hvclock_mem));
+
+	p = alloc_pages(GFP_KERNEL, order);
+	if (!p) {
+		pr_warn("%s: failed to alloc %d pages", __func__, (1U << order));
+		return;
+	}
+
+	hvclock_mem = page_address(p);
+
+	/*
+	 * hvclock is shared between the guest and the hypervisor, must
+	 * be mapped decrypted.
+	 */
+	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
+		r = set_memory_decrypted((unsigned long) hvclock_mem,
+					 1UL << order);
+		if (r) {
+			__free_pages(p, order);
+			hvclock_mem = NULL;
+			pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n");
+			return;
+		}
+	}
+
+	memset(hvclock_mem, 0, PAGE_SIZE << order);
+}
+
+static int __init kvm_setup_vsyscall_timeinfo(void)
+{
+	if (!kvm_para_available() || !kvmclock || nopv)
+		return 0;
+
+	kvmclock_init_mem();
+
+#ifdef CONFIG_X86_64
+	if (per_cpu(hv_clock_per_cpu, 0) && kvmclock_vsyscall) {
+		u8 flags;
+
+		flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
+		if (!(flags & PVCLOCK_TSC_STABLE_BIT))
+			return 0;
+
+		kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK;
+	}
+#endif
+
+	return 0;
+}
+early_initcall(kvm_setup_vsyscall_timeinfo);
+
+static int kvmclock_setup_percpu(unsigned int cpu)
+{
+	struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu);
+
+	/*
+	 * The per cpu area setup replicates CPU0 data to all cpu
+	 * pointers. So carefully check. CPU0 has been set up in init
+	 * already.
+	 */
+	if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
+		return 0;
+
+	/* Use the static page for the first CPUs, allocate otherwise */
+	if (cpu < HVC_BOOT_ARRAY_SIZE)
+		p = &hv_clock_boot[cpu];
+	else if (hvclock_mem)
+		p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE;
+	else
+		return -ENOMEM;
+
+	per_cpu(hv_clock_per_cpu, cpu) = p;
+	return p ? 0 : -ENOMEM;
+}
+
+void __init kvmclock_init(void)
+{
+	u8 flags;
+
+	if (!kvm_para_available() || !kvmclock)
+		return;
+
+	if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
+		msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
+		msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
+	} else if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
+		msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
+		msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
+	} else {
+		return;
+	}
+
+	if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
+			      kvmclock_setup_percpu, NULL) < 0) {
+		return;
+	}
+
+	pr_info("kvm-clock: Using msrs %x and %x",
+		msr_kvm_system_time, msr_kvm_wall_clock);
+
+	this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]);
+	kvm_register_clock("primary cpu clock");
+	pvclock_set_pvti_cpu0_va(hv_clock_boot);
+
+	if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
+		pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
+
+	flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
+	kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
+
+	x86_platform.calibrate_tsc = kvm_get_tsc_khz;
+	x86_platform.calibrate_cpu = kvm_get_tsc_khz;
+	x86_platform.get_wallclock = kvm_get_wallclock;
+	x86_platform.set_wallclock = kvm_set_wallclock;
+#ifdef CONFIG_X86_LOCAL_APIC
+	x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
+#endif
+	x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
+	x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
+	kvm_get_preset_lpj();
+
+	/*
+	 * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate
+	 * with P/T states and does not stop in deep C-states.
+	 *
+	 * Invariant TSC exposed by host means kvmclock is not necessary:
+	 * can use TSC as clocksource.
+	 *
+	 */
+	if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
+	    boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
+	    !check_tsc_unstable())
+		kvm_clock.rating = 299;
+
+	clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
+	pv_info.name = "KVM";
+}