From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- arch/x86/kernel/tsc_sync.c | 534 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 534 insertions(+) create mode 100644 arch/x86/kernel/tsc_sync.c (limited to 'arch/x86/kernel/tsc_sync.c') diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c new file mode 100644 index 000000000..9452dc966 --- /dev/null +++ b/arch/x86/kernel/tsc_sync.c @@ -0,0 +1,534 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * check TSC synchronization. + * + * Copyright (C) 2006, Red Hat, Inc., Ingo Molnar + * + * We check whether all boot CPUs have their TSC's synchronized, + * print a warning if not and turn off the TSC clock-source. + * + * The warp-check is point-to-point between two CPUs, the CPU + * initiating the bootup is the 'source CPU', the freshly booting + * CPU is the 'target CPU'. + * + * Only two CPUs may participate - they can enter in any order. + * ( The serial nature of the boot logic and the CPU hotplug lock + * protects against more than 2 CPUs entering this code. ) + */ +#include +#include +#include +#include +#include +#include + +struct tsc_adjust { + s64 bootval; + s64 adjusted; + unsigned long nextcheck; + bool warned; +}; + +static DEFINE_PER_CPU(struct tsc_adjust, tsc_adjust); +static struct timer_list tsc_sync_check_timer; + +/* + * TSC's on different sockets may be reset asynchronously. + * This may cause the TSC ADJUST value on socket 0 to be NOT 0. + */ +bool __read_mostly tsc_async_resets; + +void mark_tsc_async_resets(char *reason) +{ + if (tsc_async_resets) + return; + tsc_async_resets = true; + pr_info("tsc: Marking TSC async resets true due to %s\n", reason); +} + +void tsc_verify_tsc_adjust(bool resume) +{ + struct tsc_adjust *adj = this_cpu_ptr(&tsc_adjust); + s64 curval; + + if (!boot_cpu_has(X86_FEATURE_TSC_ADJUST)) + return; + + /* Skip unnecessary error messages if TSC already unstable */ + if (check_tsc_unstable()) + return; + + /* Rate limit the MSR check */ + if (!resume && time_before(jiffies, adj->nextcheck)) + return; + + adj->nextcheck = jiffies + HZ; + + rdmsrl(MSR_IA32_TSC_ADJUST, curval); + if (adj->adjusted == curval) + return; + + /* Restore the original value */ + wrmsrl(MSR_IA32_TSC_ADJUST, adj->adjusted); + + if (!adj->warned || resume) { + pr_warn(FW_BUG "TSC ADJUST differs: CPU%u %lld --> %lld. Restoring\n", + smp_processor_id(), adj->adjusted, curval); + adj->warned = true; + } +} + +/* + * Normally the tsc_sync will be checked every time system enters idle + * state, but there is still caveat that a system won't enter idle, + * either because it's too busy or configured purposely to not enter + * idle. + * + * So setup a periodic timer (every 10 minutes) to make sure the check + * is always on. + */ + +#define SYNC_CHECK_INTERVAL (HZ * 600) + +static void tsc_sync_check_timer_fn(struct timer_list *unused) +{ + int next_cpu; + + tsc_verify_tsc_adjust(false); + + /* Run the check for all onlined CPUs in turn */ + next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask); + if (next_cpu >= nr_cpu_ids) + next_cpu = cpumask_first(cpu_online_mask); + + tsc_sync_check_timer.expires += SYNC_CHECK_INTERVAL; + add_timer_on(&tsc_sync_check_timer, next_cpu); +} + +static int __init start_sync_check_timer(void) +{ + if (!cpu_feature_enabled(X86_FEATURE_TSC_ADJUST) || tsc_clocksource_reliable) + return 0; + + timer_setup(&tsc_sync_check_timer, tsc_sync_check_timer_fn, 0); + tsc_sync_check_timer.expires = jiffies + SYNC_CHECK_INTERVAL; + add_timer(&tsc_sync_check_timer); + + return 0; +} +late_initcall(start_sync_check_timer); + +static void tsc_sanitize_first_cpu(struct tsc_adjust *cur, s64 bootval, + unsigned int cpu, bool bootcpu) +{ + /* + * First online CPU in a package stores the boot value in the + * adjustment value. This value might change later via the sync + * mechanism. If that fails we still can yell about boot values not + * being consistent. + * + * On the boot cpu we just force set the ADJUST value to 0 if it's + * non zero. We don't do that on non boot cpus because physical + * hotplug should have set the ADJUST register to a value > 0 so + * the TSC is in sync with the already running cpus. + * + * Also don't force the ADJUST value to zero if that is a valid value + * for socket 0 as determined by the system arch. This is required + * when multiple sockets are reset asynchronously with each other + * and socket 0 may not have an TSC ADJUST value of 0. + */ + if (bootcpu && bootval != 0) { + if (likely(!tsc_async_resets)) { + pr_warn(FW_BUG "TSC ADJUST: CPU%u: %lld force to 0\n", + cpu, bootval); + wrmsrl(MSR_IA32_TSC_ADJUST, 0); + bootval = 0; + } else { + pr_info("TSC ADJUST: CPU%u: %lld NOT forced to 0\n", + cpu, bootval); + } + } + cur->adjusted = bootval; +} + +#ifndef CONFIG_SMP +bool __init tsc_store_and_check_tsc_adjust(bool bootcpu) +{ + struct tsc_adjust *cur = this_cpu_ptr(&tsc_adjust); + s64 bootval; + + if (!boot_cpu_has(X86_FEATURE_TSC_ADJUST)) + return false; + + /* Skip unnecessary error messages if TSC already unstable */ + if (check_tsc_unstable()) + return false; + + rdmsrl(MSR_IA32_TSC_ADJUST, bootval); + cur->bootval = bootval; + cur->nextcheck = jiffies + HZ; + tsc_sanitize_first_cpu(cur, bootval, smp_processor_id(), bootcpu); + return false; +} + +#else /* !CONFIG_SMP */ + +/* + * Store and check the TSC ADJUST MSR if available + */ +bool tsc_store_and_check_tsc_adjust(bool bootcpu) +{ + struct tsc_adjust *ref, *cur = this_cpu_ptr(&tsc_adjust); + unsigned int refcpu, cpu = smp_processor_id(); + struct cpumask *mask; + s64 bootval; + + if (!boot_cpu_has(X86_FEATURE_TSC_ADJUST)) + return false; + + rdmsrl(MSR_IA32_TSC_ADJUST, bootval); + cur->bootval = bootval; + cur->nextcheck = jiffies + HZ; + cur->warned = false; + + /* + * If a non-zero TSC value for socket 0 may be valid then the default + * adjusted value cannot assumed to be zero either. + */ + if (tsc_async_resets) + cur->adjusted = bootval; + + /* + * Check whether this CPU is the first in a package to come up. In + * this case do not check the boot value against another package + * because the new package might have been physically hotplugged, + * where TSC_ADJUST is expected to be different. When called on the + * boot CPU topology_core_cpumask() might not be available yet. + */ + mask = topology_core_cpumask(cpu); + refcpu = mask ? cpumask_any_but(mask, cpu) : nr_cpu_ids; + + if (refcpu >= nr_cpu_ids) { + tsc_sanitize_first_cpu(cur, bootval, smp_processor_id(), + bootcpu); + return false; + } + + ref = per_cpu_ptr(&tsc_adjust, refcpu); + /* + * Compare the boot value and complain if it differs in the + * package. + */ + if (bootval != ref->bootval) + printk_once(FW_BUG "TSC ADJUST differs within socket(s), fixing all errors\n"); + + /* + * The TSC_ADJUST values in a package must be the same. If the boot + * value on this newly upcoming CPU differs from the adjustment + * value of the already online CPU in this package, set it to that + * adjusted value. + */ + if (bootval != ref->adjusted) { + cur->adjusted = ref->adjusted; + wrmsrl(MSR_IA32_TSC_ADJUST, ref->adjusted); + } + /* + * We have the TSCs forced to be in sync on this package. Skip sync + * test: + */ + return true; +} + +/* + * Entry/exit counters that make sure that both CPUs + * run the measurement code at once: + */ +static atomic_t start_count; +static atomic_t stop_count; +static atomic_t skip_test; +static atomic_t test_runs; + +/* + * We use a raw spinlock in this exceptional case, because + * we want to have the fastest, inlined, non-debug version + * of a critical section, to be able to prove TSC time-warps: + */ +static arch_spinlock_t sync_lock = __ARCH_SPIN_LOCK_UNLOCKED; + +static cycles_t last_tsc; +static cycles_t max_warp; +static int nr_warps; +static int random_warps; + +/* + * TSC-warp measurement loop running on both CPUs. This is not called + * if there is no TSC. + */ +static cycles_t check_tsc_warp(unsigned int timeout) +{ + cycles_t start, now, prev, end, cur_max_warp = 0; + int i, cur_warps = 0; + + start = rdtsc_ordered(); + /* + * The measurement runs for 'timeout' msecs: + */ + end = start + (cycles_t) tsc_khz * timeout; + + for (i = 0; ; i++) { + /* + * We take the global lock, measure TSC, save the + * previous TSC that was measured (possibly on + * another CPU) and update the previous TSC timestamp. + */ + arch_spin_lock(&sync_lock); + prev = last_tsc; + now = rdtsc_ordered(); + last_tsc = now; + arch_spin_unlock(&sync_lock); + + /* + * Be nice every now and then (and also check whether + * measurement is done [we also insert a 10 million + * loops safety exit, so we dont lock up in case the + * TSC readout is totally broken]): + */ + if (unlikely(!(i & 7))) { + if (now > end || i > 10000000) + break; + cpu_relax(); + touch_nmi_watchdog(); + } + /* + * Outside the critical section we can now see whether + * we saw a time-warp of the TSC going backwards: + */ + if (unlikely(prev > now)) { + arch_spin_lock(&sync_lock); + max_warp = max(max_warp, prev - now); + cur_max_warp = max_warp; + /* + * Check whether this bounces back and forth. Only + * one CPU should observe time going backwards. + */ + if (cur_warps != nr_warps) + random_warps++; + nr_warps++; + cur_warps = nr_warps; + arch_spin_unlock(&sync_lock); + } + } + WARN(!(now-start), + "Warning: zero tsc calibration delta: %Ld [max: %Ld]\n", + now-start, end-start); + return cur_max_warp; +} + +/* + * If the target CPU coming online doesn't have any of its core-siblings + * online, a timeout of 20msec will be used for the TSC-warp measurement + * loop. Otherwise a smaller timeout of 2msec will be used, as we have some + * information about this socket already (and this information grows as we + * have more and more logical-siblings in that socket). + * + * Ideally we should be able to skip the TSC sync check on the other + * core-siblings, if the first logical CPU in a socket passed the sync test. + * But as the TSC is per-logical CPU and can potentially be modified wrongly + * by the bios, TSC sync test for smaller duration should be able + * to catch such errors. Also this will catch the condition where all the + * cores in the socket don't get reset at the same time. + */ +static inline unsigned int loop_timeout(int cpu) +{ + return (cpumask_weight(topology_core_cpumask(cpu)) > 1) ? 2 : 20; +} + +/* + * Source CPU calls into this - it waits for the freshly booted + * target CPU to arrive and then starts the measurement: + */ +void check_tsc_sync_source(int cpu) +{ + int cpus = 2; + + /* + * No need to check if we already know that the TSC is not + * synchronized or if we have no TSC. + */ + if (unsynchronized_tsc()) + return; + + /* + * Set the maximum number of test runs to + * 1 if the CPU does not provide the TSC_ADJUST MSR + * 3 if the MSR is available, so the target can try to adjust + */ + if (!boot_cpu_has(X86_FEATURE_TSC_ADJUST)) + atomic_set(&test_runs, 1); + else + atomic_set(&test_runs, 3); +retry: + /* + * Wait for the target to start or to skip the test: + */ + while (atomic_read(&start_count) != cpus - 1) { + if (atomic_read(&skip_test) > 0) { + atomic_set(&skip_test, 0); + return; + } + cpu_relax(); + } + + /* + * Trigger the target to continue into the measurement too: + */ + atomic_inc(&start_count); + + check_tsc_warp(loop_timeout(cpu)); + + while (atomic_read(&stop_count) != cpus-1) + cpu_relax(); + + /* + * If the test was successful set the number of runs to zero and + * stop. If not, decrement the number of runs an check if we can + * retry. In case of random warps no retry is attempted. + */ + if (!nr_warps) { + atomic_set(&test_runs, 0); + + pr_debug("TSC synchronization [CPU#%d -> CPU#%d]: passed\n", + smp_processor_id(), cpu); + + } else if (atomic_dec_and_test(&test_runs) || random_warps) { + /* Force it to 0 if random warps brought us here */ + atomic_set(&test_runs, 0); + + pr_warn("TSC synchronization [CPU#%d -> CPU#%d]:\n", + smp_processor_id(), cpu); + pr_warn("Measured %Ld cycles TSC warp between CPUs, " + "turning off TSC clock.\n", max_warp); + if (random_warps) + pr_warn("TSC warped randomly between CPUs\n"); + mark_tsc_unstable("check_tsc_sync_source failed"); + } + + /* + * Reset it - just in case we boot another CPU later: + */ + atomic_set(&start_count, 0); + random_warps = 0; + nr_warps = 0; + max_warp = 0; + last_tsc = 0; + + /* + * Let the target continue with the bootup: + */ + atomic_inc(&stop_count); + + /* + * Retry, if there is a chance to do so. + */ + if (atomic_read(&test_runs) > 0) + goto retry; +} + +/* + * Freshly booted CPUs call into this: + */ +void check_tsc_sync_target(void) +{ + struct tsc_adjust *cur = this_cpu_ptr(&tsc_adjust); + unsigned int cpu = smp_processor_id(); + cycles_t cur_max_warp, gbl_max_warp; + int cpus = 2; + + /* Also aborts if there is no TSC. */ + if (unsynchronized_tsc()) + return; + + /* + * Store, verify and sanitize the TSC adjust register. If + * successful skip the test. + * + * The test is also skipped when the TSC is marked reliable. This + * is true for SoCs which have no fallback clocksource. On these + * SoCs the TSC is frequency synchronized, but still the TSC ADJUST + * register might have been wreckaged by the BIOS.. + */ + if (tsc_store_and_check_tsc_adjust(false) || tsc_clocksource_reliable) { + atomic_inc(&skip_test); + return; + } + +retry: + /* + * Register this CPU's participation and wait for the + * source CPU to start the measurement: + */ + atomic_inc(&start_count); + while (atomic_read(&start_count) != cpus) + cpu_relax(); + + cur_max_warp = check_tsc_warp(loop_timeout(cpu)); + + /* + * Store the maximum observed warp value for a potential retry: + */ + gbl_max_warp = max_warp; + + /* + * Ok, we are done: + */ + atomic_inc(&stop_count); + + /* + * Wait for the source CPU to print stuff: + */ + while (atomic_read(&stop_count) != cpus) + cpu_relax(); + + /* + * Reset it for the next sync test: + */ + atomic_set(&stop_count, 0); + + /* + * Check the number of remaining test runs. If not zero, the test + * failed and a retry with adjusted TSC is possible. If zero the + * test was either successful or failed terminally. + */ + if (!atomic_read(&test_runs)) + return; + + /* + * If the warp value of this CPU is 0, then the other CPU + * observed time going backwards so this TSC was ahead and + * needs to move backwards. + */ + if (!cur_max_warp) + cur_max_warp = -gbl_max_warp; + + /* + * Add the result to the previous adjustment value. + * + * The adjustment value is slightly off by the overhead of the + * sync mechanism (observed values are ~200 TSC cycles), but this + * really depends on CPU, node distance and frequency. So + * compensating for this is hard to get right. Experiments show + * that the warp is not longer detectable when the observed warp + * value is used. In the worst case the adjustment needs to go + * through a 3rd run for fine tuning. + */ + cur->adjusted += cur_max_warp; + + pr_warn("TSC ADJUST compensate: CPU%u observed %lld warp. Adjust: %lld\n", + cpu, cur_max_warp, cur->adjusted); + + wrmsrl(MSR_IA32_TSC_ADJUST, cur->adjusted); + goto retry; + +} + +#endif /* CONFIG_SMP */ -- cgit v1.2.3