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- // 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 = MSR_KVM_SYSTEM_TIME;
- static int msr_kvm_wall_clock __ro_after_init = MSR_KVM_WALL_CLOCK;
- 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)
- {
- 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)) {
- 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";
- }
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