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Hall" , Richard Cochran Content-Type: text/plain; charset="UTF-8" Configure the pKVM hypervisor tracing clock with the kernel boot clock. For tracing purpose, the boot clock is interesting as it doesn't stop on suspend. However, it is corrected on a regular basis, which implies we need to re-evaluate it every once in a while. Cc: John Stultz Cc: Thomas Gleixner Cc: Stephen Boyd Cc: Christopher S. Hall Cc: Richard Cochran Signed-off-by: Vincent Donnefort diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index 437ac948d136..d122d79718a0 100644 --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -87,6 +87,7 @@ enum __kvm_host_smccc_func { __KVM_HOST_SMCCC_FUNC___pkvm_vcpu_load, __KVM_HOST_SMCCC_FUNC___pkvm_vcpu_put, __KVM_HOST_SMCCC_FUNC___pkvm_tlb_flush_vmid, + __KVM_HOST_SMCCC_FUNC___pkvm_update_clock_tracing, __KVM_HOST_SMCCC_FUNC___pkvm_load_tracing, __KVM_HOST_SMCCC_FUNC___pkvm_unload_tracing, __KVM_HOST_SMCCC_FUNC___pkvm_enable_tracing, diff --git a/arch/arm64/kvm/hyp/include/nvhe/trace.h b/arch/arm64/kvm/hyp/include/nvhe/trace.h index 996e90c0974f..4e11dcdf049b 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/trace.h +++ b/arch/arm64/kvm/hyp/include/nvhe/trace.h @@ -7,6 +7,7 @@ void *tracing_reserve_entry(unsigned long length); void tracing_commit_entry(void); +void __pkvm_update_clock_tracing(u32 mult, u32 shift, u64 epoch_ns, u64 epoch_cyc); int __pkvm_load_tracing(unsigned long desc_va, size_t desc_size); void __pkvm_unload_tracing(void); int __pkvm_enable_tracing(bool enable); @@ -15,6 +16,8 @@ int __pkvm_swap_reader_tracing(unsigned int cpu); static inline void *tracing_reserve_entry(unsigned long length) { return NULL; } static inline void tracing_commit_entry(void) { } +static inline +void __pkvm_update_clock_tracing(u32 mult, u32 shift, u64 epoch_ns, u64 epoch_cyc) { } static inline int __pkvm_load_tracing(unsigned long desc_va, size_t desc_size) { return -ENODEV; } static inline void __pkvm_unload_tracing(void) { } static inline int __pkvm_enable_tracing(bool enable) { return -ENODEV; } diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index 02b2fdd9a8e4..36a263422e4e 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -574,6 +574,18 @@ static void handle___pkvm_teardown_vm(struct kvm_cpu_context *host_ctxt) cpu_reg(host_ctxt, 1) = __pkvm_teardown_vm(handle); } +static void handle___pkvm_update_clock_tracing(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(u32, mult, host_ctxt, 1); + DECLARE_REG(u32, shift, host_ctxt, 2); + DECLARE_REG(u64, epoch_ns, host_ctxt, 3); + DECLARE_REG(u64, epoch_cyc, host_ctxt, 4); + + __pkvm_update_clock_tracing(mult, shift, epoch_ns, epoch_cyc); + + cpu_reg(host_ctxt, 1) = 0; +} + static void handle___pkvm_load_tracing(struct kvm_cpu_context *host_ctxt) { DECLARE_REG(unsigned long, desc_hva, host_ctxt, 1); @@ -642,6 +654,7 @@ static const hcall_t host_hcall[] = { HANDLE_FUNC(__pkvm_vcpu_load), HANDLE_FUNC(__pkvm_vcpu_put), HANDLE_FUNC(__pkvm_tlb_flush_vmid), + HANDLE_FUNC(__pkvm_update_clock_tracing), HANDLE_FUNC(__pkvm_load_tracing), HANDLE_FUNC(__pkvm_unload_tracing), HANDLE_FUNC(__pkvm_enable_tracing), diff --git a/arch/arm64/kvm/hyp/nvhe/trace.c b/arch/arm64/kvm/hyp/nvhe/trace.c index def5cbc75722..d146ac3046de 100644 --- a/arch/arm64/kvm/hyp/nvhe/trace.c +++ b/arch/arm64/kvm/hyp/nvhe/trace.c @@ -255,3 +255,19 @@ int __pkvm_swap_reader_tracing(unsigned int cpu) return ret; } + +void __pkvm_update_clock_tracing(u32 mult, u32 shift, u64 epoch_ns, u64 epoch_cyc) +{ + int cpu; + + /* After this loop, all CPUs are observing the new bank... */ + for (cpu = 0; cpu < hyp_nr_cpus; cpu++) { + struct simple_rb_per_cpu *simple_rb = per_cpu_ptr(trace_buffer.simple_rbs, cpu); + + while (READ_ONCE(simple_rb->status) == SIMPLE_RB_WRITING) + ; + } + + /* ...we can now override the old one and swap. */ + trace_clock_update(mult, shift, epoch_ns, epoch_cyc); +} diff --git a/arch/arm64/kvm/hyp_trace.c b/arch/arm64/kvm/hyp_trace.c index 98051c3fb0c2..4f154ec743f3 100644 --- a/arch/arm64/kvm/hyp_trace.c +++ b/arch/arm64/kvm/hyp_trace.c @@ -5,6 +5,7 @@ */ #include +#include #include #include @@ -12,6 +13,121 @@ #include "hyp_trace.h" +/* Same 10min used by clocksource when width is more than 32-bits */ +#define CLOCK_MAX_CONVERSION_S 600 +/* + * Time to give for the clock init. Long enough to get a good mult/shift + * estimation. Short enough to not delay the tracing start too much. + */ +#define CLOCK_INIT_MS 100 +/* + * Time between clock checks. Must be small enough to catch clock deviation when + * it is still tiny. + */ +#define CLOCK_UPDATE_MS 500 + +static struct hyp_trace_clock { + u64 cycles; + u64 cyc_overflow64; + u64 boot; + u32 mult; + u32 shift; + struct delayed_work work; + struct completion ready; + struct mutex lock; + bool running; +} hyp_clock; + +static void __hyp_clock_work(struct work_struct *work) +{ + struct delayed_work *dwork = to_delayed_work(work); + struct hyp_trace_clock *hyp_clock; + struct system_time_snapshot snap; + u64 rate, delta_cycles; + u64 boot, delta_boot; + + hyp_clock = container_of(dwork, struct hyp_trace_clock, work); + + ktime_get_snapshot(&snap); + boot = ktime_to_ns(snap.boot); + + delta_boot = boot - hyp_clock->boot; + delta_cycles = snap.cycles - hyp_clock->cycles; + + /* Compare hyp clock with the kernel boot clock */ + if (hyp_clock->mult) { + u64 err, cur = delta_cycles; + + if (WARN_ON_ONCE(cur >= hyp_clock->cyc_overflow64)) { + __uint128_t tmp = (__uint128_t)cur * hyp_clock->mult; + + cur = tmp >> hyp_clock->shift; + } else { + cur *= hyp_clock->mult; + cur >>= hyp_clock->shift; + } + cur += hyp_clock->boot; + + err = abs_diff(cur, boot); + /* No deviation, only update epoch if necessary */ + if (!err) { + if (delta_cycles >= (hyp_clock->cyc_overflow64 >> 1)) + goto fast_forward; + + goto resched; + } + + /* Warn if the error is above tracing precision (1us) */ + if (err > NSEC_PER_USEC) + pr_warn_ratelimited("hyp trace clock off by %lluus\n", + err / NSEC_PER_USEC); + } + + rate = div64_u64(delta_cycles * NSEC_PER_SEC, delta_boot); + + clocks_calc_mult_shift(&hyp_clock->mult, &hyp_clock->shift, + rate, NSEC_PER_SEC, CLOCK_MAX_CONVERSION_S); + + /* Add a comfortable 50% margin */ + hyp_clock->cyc_overflow64 = (U64_MAX / hyp_clock->mult) >> 1; + +fast_forward: + hyp_clock->cycles = snap.cycles; + hyp_clock->boot = boot; + kvm_call_hyp_nvhe(__pkvm_update_clock_tracing, hyp_clock->mult, + hyp_clock->shift, hyp_clock->boot, hyp_clock->cycles); + complete(&hyp_clock->ready); + +resched: + schedule_delayed_work(&hyp_clock->work, + msecs_to_jiffies(CLOCK_UPDATE_MS)); +} + +static void hyp_trace_clock_enable(struct hyp_trace_clock *hyp_clock, bool enable) +{ + struct system_time_snapshot snap; + + if (hyp_clock->running == enable) + return; + + if (!enable) { + cancel_delayed_work_sync(&hyp_clock->work); + hyp_clock->running = false; + } + + ktime_get_snapshot(&snap); + + hyp_clock->boot = ktime_to_ns(snap.boot); + hyp_clock->cycles = snap.cycles; + hyp_clock->mult = 0; + + init_completion(&hyp_clock->ready); + INIT_DELAYED_WORK(&hyp_clock->work, __hyp_clock_work); + schedule_delayed_work(&hyp_clock->work, msecs_to_jiffies(CLOCK_INIT_MS)); + wait_for_completion(&hyp_clock->ready); + hyp_clock->running = true; +} + /* Access to this struct within the trace_remote_callbacks are protected by the trace_remote lock */ static struct hyp_trace_buffer { struct hyp_trace_desc *desc; @@ -174,6 +290,8 @@ static void hyp_trace_unload(struct trace_buffer_desc *desc, void *priv) static int hyp_trace_enable_tracing(bool enable, void *priv) { + hyp_trace_clock_enable(&hyp_clock, enable); + return kvm_call_hyp_nvhe(__pkvm_enable_tracing, enable); } @@ -192,7 +310,22 @@ static int hyp_trace_enable_event(unsigned short id, bool enable, void *priv) return 0; } +static int hyp_trace_clock_show(struct seq_file *m, void *v) +{ + seq_puts(m, "[boot]\n"); + + return 0; +} +DEFINE_SHOW_ATTRIBUTE(hyp_trace_clock); + +static int hyp_trace_init_tracefs(struct dentry *d, void *priv) +{ + return tracefs_create_file("trace_clock", 0440, d, NULL, &hyp_trace_clock_fops) ? + 0 : -ENOMEM; +} + static struct trace_remote_callbacks trace_remote_callbacks = { + .init = hyp_trace_init_tracefs, .load_trace_buffer = hyp_trace_load, .unload_trace_buffer = hyp_trace_unload, .enable_tracing = hyp_trace_enable_tracing, -- 2.51.0.618.g983fd99d29-goog