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FROMLIST: KVM: arm64: Add clock for hyp tracefs

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Configure the hypervisor tracing clock before starting tracing. 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.

Bug: 357781595
Link: https://lore.kernel.org/all/20240911093029.3279154-10-vdonnefort@google.com/
Cc: John Stultz <jstultz@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Christopher S. Hall <christopher.s.hall@intel.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Lakshmi Sowjanya D <lakshmi.sowjanya.d@intel.com>
Change-Id: I6fbd1a66a7c420626deb61bbd411c820ec978130
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
This commit is contained in:
Vincent Donnefort
2024-09-05 17:11:36 +01:00
committed by Keir Fraser
parent b20b64b1c4
commit 2dc09955d6
5 changed files with 168 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
arch/arm64/include/asm/kvm_asm.h
+1
View File
@@ -85,6 +85,7 @@ enum __kvm_host_smccc_func {
__KVM_HOST_SMCCC_FUNC___pkvm_vcpu_load,
__KVM_HOST_SMCCC_FUNC___pkvm_vcpu_put,
__KVM_HOST_SMCCC_FUNC___pkvm_vcpu_sync_state,
__KVM_HOST_SMCCC_FUNC___pkvm_update_clock_tracing,
__KVM_HOST_SMCCC_FUNC___pkvm_load_tracing,
__KVM_HOST_SMCCC_FUNC___pkvm_teardown_tracing,
__KVM_HOST_SMCCC_FUNC___pkvm_enable_tracing,
arch/arm64/kvm/hyp/include/nvhe/trace.h
+3
View File
@@ -16,6 +16,7 @@ struct hyp_buffer_page {
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_teardown_tracing(void);
int __pkvm_enable_tracing(bool enable);
@@ -24,6 +25,8 @@ 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_teardown_tracing(void) { }
static inline int __pkvm_enable_tracing(bool enable) { return -ENODEV; }
arch/arm64/kvm/hyp/nvhe/hyp-main.c
+13
View File
@@ -1209,6 +1209,18 @@ static void handle___pkvm_finalize_teardown_vm(struct kvm_cpu_context *host_ctxt
cpu_reg(host_ctxt, 1) = __pkvm_finalize_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);
@@ -1275,6 +1287,7 @@ static const hcall_t host_hcall[] = {
HANDLE_FUNC(__pkvm_vcpu_load),
HANDLE_FUNC(__pkvm_vcpu_put),
HANDLE_FUNC(__pkvm_vcpu_sync_state),
HANDLE_FUNC(__pkvm_update_clock_tracing),
HANDLE_FUNC(__pkvm_load_tracing),
HANDLE_FUNC(__pkvm_teardown_tracing),
HANDLE_FUNC(__pkvm_enable_tracing),
arch/arm64/kvm/hyp/nvhe/trace.c
+15
View File
@@ -468,6 +468,21 @@ static void rb_teardown_bpage_backing(void)
hyp_buffer_pages_backing.size = 0;
}
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 hyp_rb_per_cpu *cpu_buffer = per_cpu_ptr(&trace_rb, cpu);
while (atomic_read(&cpu_buffer->status) == HYP_RB_WRITING);
}
/* ...we can now override the old one and swap. */
trace_clock_update(mult, shift, epoch_ns, epoch_cyc);
}
int __pkvm_swap_reader_tracing(unsigned int cpu)
{
struct hyp_rb_per_cpu *cpu_buffer;
arch/arm64/kvm/hyp_trace.c
+136
View File
@@ -16,10 +16,25 @@
#define RB_POLL_MS 100
/* Same 10min used by clocksource when width is more than 32-bits */
#define CLOCK_MAX_CONVERSION_S 600
#define CLOCK_INIT_MS 100
#define CLOCK_POLL_MS 500
#define TRACEFS_DIR "hypervisor"
#define TRACEFS_MODE_WRITE 0640
#define TRACEFS_MODE_READ 0440
struct hyp_trace_clock {
u64 cycles;
u64 max_delta;
u64 boot;
u32 mult;
u32 shift;
struct delayed_work work;
struct completion ready;
};
static struct hyp_trace_buffer {
struct hyp_trace_desc *desc;
struct ring_buffer_writer writer;
@@ -28,6 +43,7 @@ static struct hyp_trace_buffer {
bool tracing_on;
int nr_readers;
struct mutex lock;
struct hyp_trace_clock clock;
} hyp_trace_buffer = {
.lock = __MUTEX_INITIALIZER(hyp_trace_buffer.lock),
};
@@ -74,6 +90,107 @@ bpage_backing_free(struct hyp_buffer_pages_backing *bpage_backing)
free_pages_exact((void *)bpage_backing->start, bpage_backing->size);
}
static void __hyp_clock_work(struct work_struct *work)
{
struct delayed_work *dwork = to_delayed_work(work);
struct hyp_trace_buffer *hyp_buffer;
struct hyp_trace_clock *hyp_clock;
struct system_time_snapshot snap;
u64 rate, delta_cycles;
u64 boot, delta_boot;
u64 err = 0;
hyp_clock = container_of(dwork, struct hyp_trace_clock, work);
hyp_buffer = container_of(hyp_clock, struct hyp_trace_buffer, clock);
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 cur = delta_cycles;
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->max_delta)
goto update_hyp;
goto resched;
}
/* Warn if the error is above tracing precision (1us) */
if (hyp_buffer->tracing_on && err > NSEC_PER_USEC)
pr_warn_ratelimited("hyp trace clock off by %lluus\n",
err / NSEC_PER_USEC);
}
if (delta_boot > U32_MAX) {
do_div(delta_boot, NSEC_PER_SEC);
rate = delta_cycles;
} else {
rate = delta_cycles * NSEC_PER_SEC;
}
do_div(rate, delta_boot);
clocks_calc_mult_shift(&hyp_clock->mult, &hyp_clock->shift,
rate, NSEC_PER_SEC, CLOCK_MAX_CONVERSION_S);
update_hyp:
hyp_clock->max_delta = (U64_MAX / hyp_clock->mult) >> 1;
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);
pr_debug("hyp trace clock update mult=%u shift=%u max_delta=%llu err=%llu\n",
hyp_clock->mult, hyp_clock->shift, hyp_clock->max_delta, err);
resched:
schedule_delayed_work(&hyp_clock->work,
msecs_to_jiffies(CLOCK_POLL_MS));
}
static void hyp_clock_start(struct hyp_trace_buffer *hyp_buffer)
{
struct hyp_trace_clock *hyp_clock = &hyp_buffer->clock;
struct system_time_snapshot snap;
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));
}
static void hyp_clock_stop(struct hyp_trace_buffer *hyp_buffer)
{
struct hyp_trace_clock *hyp_clock = &hyp_buffer->clock;
cancel_delayed_work_sync(&hyp_clock->work);
}
static void hyp_clock_wait(struct hyp_trace_buffer *hyp_buffer)
{
struct hyp_trace_clock *hyp_clock = &hyp_buffer->clock;
wait_for_completion(&hyp_clock->ready);
}
static int __get_reader_page(int cpu)
{
return kvm_call_hyp_nvhe(__pkvm_swap_reader_tracing, cpu);
@@ -294,10 +411,14 @@ static int hyp_trace_start(void)
if (hyp_buffer->tracing_on)
goto out;
hyp_clock_start(hyp_buffer);
ret = hyp_trace_buffer_load(hyp_buffer, hyp_trace_buffer_size);
if (ret)
goto out;
hyp_clock_wait(hyp_buffer);
ret = kvm_call_hyp_nvhe(__pkvm_enable_tracing, true);
if (ret) {
hyp_trace_buffer_teardown(hyp_buffer);
@@ -307,6 +428,9 @@ static int hyp_trace_start(void)
hyp_buffer->tracing_on = true;
out:
if (!hyp_buffer->tracing_on)
hyp_clock_stop(hyp_buffer);
mutex_unlock(&hyp_buffer->lock);
return ret;
@@ -324,6 +448,7 @@ static void hyp_trace_stop(void)
ret = kvm_call_hyp_nvhe(__pkvm_enable_tracing, false);
if (!ret) {
hyp_clock_stop(hyp_buffer);
ring_buffer_poll_writer(hyp_buffer->trace_buffer,
RING_BUFFER_ALL_CPUS);
hyp_buffer->tracing_on = false;
@@ -614,6 +739,14 @@ static const struct file_operations hyp_trace_pipe_fops = {
.release = hyp_trace_pipe_release,
};
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);
int hyp_trace_init_tracefs(void)
{
struct dentry *root, *per_cpu_root;
@@ -638,6 +771,9 @@ int hyp_trace_init_tracefs(void)
tracefs_create_file("trace_pipe", TRACEFS_MODE_WRITE, root,
(void *)RING_BUFFER_ALL_CPUS, &hyp_trace_pipe_fops);
tracefs_create_file("trace_clock", TRACEFS_MODE_READ, root, NULL,
&hyp_trace_clock_fops);
per_cpu_root = tracefs_create_dir("per_cpu", root);
if (!per_cpu_root) {
pr_err("Failed to create tracefs folder "TRACEFS_DIR"/per_cpu/\n");