// 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 <asm/hypervisor.h> #include <asm/mem_encrypt.h> #include <asm/x86_init.h> #include <asm/reboot.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 HV_CLOCK_SIZE (sizeof(struct pvclock_vsyscall_time_info) * NR_CPUS) #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 DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu); static struct pvclock_vsyscall_time_info *hvclock_mem; static inline struct pvclock_vcpu_time_info *this_cpu_pvti(void) { return &this_cpu_read(hv_clock_per_cpu)->pvti; } static inline struct pvclock_vsyscall_time_info *this_cpu_hvclock(void) { return this_cpu_read(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(); pv_ops.time.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; } struct clocksource kvm_clock = { .name = "kvm-clock", .read = kvm_clock_get_cycles, .rating = 400, .mask = CLOCKSOURCE_MASK(64), .flags = CLOCK_SOURCE_IS_CONTINUOUS, }; 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_info("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 /* * After the clock is registered, the host will keep writing to the * registered memory location. If the guest happens to shutdown, this memory * won't be valid. In cases like kexec, in which you install a new kernel, this * means a random memory location will be kept being written. So before any * kind of shutdown from our side, we unregister the clock by writing anything * that does not have the 'enable' bit set in the msr */ #ifdef CONFIG_KEXEC_CORE static void kvm_crash_shutdown(struct pt_regs *regs) { native_write_msr(msr_kvm_system_time, 0, 0); kvm_disable_steal_time(); native_machine_crash_shutdown(regs); } #endif static void kvm_shutdown(void) { native_write_msr(msr_kvm_system_time, 0, 0); kvm_disable_steal_time(); native_machine_shutdown(); } 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 (sev_active()) { 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) { #ifdef CONFIG_X86_64 u8 flags; if (!per_cpu(hv_clock_per_cpu, 0) || !kvmclock_vsyscall) return 0; flags = pvclock_read_flags(&hv_clock_boot[0].pvti); if (!(flags & PVCLOCK_TSC_STABLE_BIT)) return 0; kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK; #endif kvmclock_init_mem(); 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; machine_ops.shutdown = kvm_shutdown; #ifdef CONFIG_KEXEC_CORE machine_ops.crash_shutdown = kvm_crash_shutdown; #endif 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"; }