When running with KVM protected mode, the hypervisor is able to generate events into tracefs compatible ring-buffers. Plug those ring-buffers to tracefs. The interface is found in hyp/ and contains the same hierarchy as any host instances easing the support by existing user-space tools.
This currently doesn't provide any event support which will come later. Signed-off-by: Vincent Donnefort <[email protected]> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile index 3cf7adb2b503..865971bb8905 100644 --- a/arch/arm64/kvm/Makefile +++ b/arch/arm64/kvm/Makefile @@ -29,6 +29,8 @@ kvm-$(CONFIG_HW_PERF_EVENTS) += pmu-emul.o pmu.o kvm-$(CONFIG_ARM64_PTR_AUTH) += pauth.o kvm-$(CONFIG_PTDUMP_STAGE2_DEBUGFS) += ptdump.o +kvm-$(CONFIG_TRACING) += hyp_trace.o + always-y := hyp_constants.h hyp-constants.s define rule_gen_hyp_constants diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index a102c3aebdbc..cef933eb1cd4 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -25,6 +25,7 @@ #define CREATE_TRACE_POINTS #include "trace_arm.h" +#include "hyp_trace.h" #include <linux/uaccess.h> #include <asm/ptrace.h> @@ -2316,6 +2317,9 @@ static int __init init_subsystems(void) kvm_register_perf_callbacks(NULL); + err = hyp_trace_init_tracefs(); + if (err) + kvm_err("Failed to initialize Hyp tracing\n"); out: if (err) hyp_cpu_pm_exit(); diff --git a/arch/arm64/kvm/hyp/hyp-constants.c b/arch/arm64/kvm/hyp/hyp-constants.c index b257a3b4bfc5..5c4a797a701f 100644 --- a/arch/arm64/kvm/hyp/hyp-constants.c +++ b/arch/arm64/kvm/hyp/hyp-constants.c @@ -3,11 +3,15 @@ #include <linux/kbuild.h> #include <nvhe/memory.h> #include <nvhe/pkvm.h> +#include <nvhe/trace.h> int main(void) { DEFINE(STRUCT_HYP_PAGE_SIZE, sizeof(struct hyp_page)); DEFINE(PKVM_HYP_VM_SIZE, sizeof(struct pkvm_hyp_vm)); DEFINE(PKVM_HYP_VCPU_SIZE, sizeof(struct pkvm_hyp_vcpu)); +#ifdef CONFIG_TRACING + DEFINE(STRUCT_HYP_BUFFER_PAGE_SIZE, sizeof(struct hyp_buffer_page)); +#endif return 0; } diff --git a/arch/arm64/kvm/hyp_trace.c b/arch/arm64/kvm/hyp_trace.c new file mode 100644 index 000000000000..be5bc602abc4 --- /dev/null +++ b/arch/arm64/kvm/hyp_trace.c @@ -0,0 +1,663 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2024 Google LLC + * Author: Vincent Donnefort <[email protected]> + */ + +#include <linux/arm-smccc.h> +#include <linux/percpu-defs.h> +#include <linux/tracefs.h> + +#include <asm/kvm_host.h> +#include <asm/kvm_hyptrace.h> + +#include "hyp_constants.h" +#include "hyp_trace.h" + +#define RB_POLL_MS 100 + +#define TRACEFS_DIR "hypervisor" +#define TRACEFS_MODE_WRITE 0640 +#define TRACEFS_MODE_READ 0440 + +static struct hyp_trace_buffer { + struct hyp_trace_desc *desc; + struct ring_buffer_remote remote; + struct trace_buffer *trace_buffer; + size_t desc_size; + bool tracing_on; + int nr_readers; + struct mutex lock; +} hyp_trace_buffer = { + .lock = __MUTEX_INITIALIZER(hyp_trace_buffer.lock), +}; + +static size_t hyp_trace_buffer_size = 7 << 10; + +/* Number of pages the ring-buffer requires to accommodate for size */ +#define NR_PAGES(size) \ + ((PAGE_ALIGN(size) >> PAGE_SHIFT) + 1) + +static inline bool hyp_trace_buffer_loaded(struct hyp_trace_buffer *hyp_buffer) +{ + return !!hyp_buffer->trace_buffer; +} + +static inline bool hyp_trace_buffer_used(struct hyp_trace_buffer *hyp_buffer) +{ + return hyp_buffer->nr_readers || hyp_buffer->tracing_on || + !ring_buffer_empty(hyp_buffer->trace_buffer); +} + +static int +bpage_backing_alloc(struct hyp_buffer_pages_backing *bpage_backing, size_t size) +{ + size_t backing_size; + void *start; + + backing_size = PAGE_ALIGN(STRUCT_HYP_BUFFER_PAGE_SIZE * NR_PAGES(size) * + num_possible_cpus()); + + start = alloc_pages_exact(backing_size, GFP_KERNEL_ACCOUNT); + if (!start) + return -ENOMEM; + + bpage_backing->start = (unsigned long)start; + bpage_backing->size = backing_size; + + return 0; +} + +static void +bpage_backing_free(struct hyp_buffer_pages_backing *bpage_backing) +{ + free_pages_exact((void *)bpage_backing->start, bpage_backing->size); +} + +static int __get_reader_page(int cpu) +{ + return kvm_call_hyp_nvhe(__pkvm_swap_reader_tracing, cpu); +} + +static void hyp_trace_free_pages(struct hyp_trace_desc *desc) +{ + struct rb_page_desc *rb_desc; + int cpu, id; + + for_each_rb_page_desc(rb_desc, cpu, &desc->page_desc) { + free_page(rb_desc->meta_va); + for (id = 0; id < rb_desc->nr_page_va; id++) + free_page(rb_desc->page_va[id]); + } +} + +static int hyp_trace_alloc_pages(struct hyp_trace_desc *desc, size_t size) +{ + int err = 0, cpu, id, nr_pages = NR_PAGES(size); + struct trace_page_desc *trace_desc; + struct rb_page_desc *rb_desc; + + trace_desc = &desc->page_desc; + trace_desc->nr_cpus = 0; + + rb_desc = (struct rb_page_desc *)&trace_desc->__data[0]; + + for_each_possible_cpu(cpu) { + rb_desc->cpu = cpu; + rb_desc->nr_page_va = 0; + rb_desc->meta_va = (unsigned long)page_to_virt(alloc_page(GFP_KERNEL)); + if (!rb_desc->meta_va) { + err = -ENOMEM; + break; + } + for (id = 0; id < nr_pages; id++) { + rb_desc->page_va[id] = (unsigned long)page_to_virt(alloc_page(GFP_KERNEL)); + if (!rb_desc->page_va[id]) { + err = -ENOMEM; + break; + } + rb_desc->nr_page_va++; + } + trace_desc->nr_cpus++; + rb_desc = __next_rb_page_desc(rb_desc); + } + + if (err) { + hyp_trace_free_pages(desc); + return err; + } + + return 0; +} + +static int __load_page(unsigned long va) +{ + return kvm_call_hyp_nvhe(__pkvm_host_share_hyp, virt_to_pfn((void *)va), 1); +} + +static void __teardown_page(unsigned long va) +{ + WARN_ON(kvm_call_hyp_nvhe(__pkvm_host_unshare_hyp, virt_to_pfn((void *)va), 1)); +} + +static void hyp_trace_teardown_pages(struct hyp_trace_desc *desc, + int last_cpu) +{ + struct rb_page_desc *rb_desc; + int cpu, id; + + for_each_rb_page_desc(rb_desc, cpu, &desc->page_desc) { + if (cpu > last_cpu) + break; + __teardown_page(rb_desc->meta_va); + for (id = 0; id < rb_desc->nr_page_va; id++) + __teardown_page(rb_desc->page_va[id]); + } +} + +static int hyp_trace_load_pages(struct hyp_trace_desc *desc) +{ + int last_loaded_cpu = 0, cpu, id, err = -EINVAL; + struct rb_page_desc *rb_desc; + + for_each_rb_page_desc(rb_desc, cpu, &desc->page_desc) { + err = __load_page(rb_desc->meta_va); + if (err) + break; + + for (id = 0; id < rb_desc->nr_page_va; id++) { + err = __load_page(rb_desc->page_va[id]); + if (err) + break; + } + + if (!err) + continue; + + for (id--; id >= 0; id--) + __teardown_page(rb_desc->page_va[id]); + + last_loaded_cpu = cpu - 1; + + break; + } + + if (!err) + return 0; + + hyp_trace_teardown_pages(desc, last_loaded_cpu); + + return err; +} + +static int hyp_trace_buffer_load(struct hyp_trace_buffer *hyp_buffer, size_t size) +{ + int ret, nr_pages = NR_PAGES(size); + struct rb_page_desc *rbdesc; + struct hyp_trace_desc *desc; + size_t desc_size; + + if (hyp_trace_buffer_loaded(hyp_buffer)) + return 0; + + desc_size = size_add(offsetof(struct hyp_trace_desc, page_desc), + offsetof(struct trace_page_desc, __data)); + desc_size = size_add(desc_size, + size_mul(num_possible_cpus(), + struct_size(rbdesc, page_va, nr_pages))); + if (desc_size == SIZE_MAX) + return -E2BIG; + + /* + * The hypervisor will unmap the descriptor from the host to protect the + * reading. Page granularity for the allocation ensures no other + * useful data will be unmapped. + */ + desc_size = PAGE_ALIGN(desc_size); + + desc = (struct hyp_trace_desc *)alloc_pages_exact(desc_size, GFP_KERNEL); + if (!desc) + return -ENOMEM; + + ret = hyp_trace_alloc_pages(desc, size); + if (ret) + goto err_free_desc; + + ret = bpage_backing_alloc(&desc->backing, size); + if (ret) + goto err_free_pages; + + ret = hyp_trace_load_pages(desc); + if (ret) + goto err_free_backing; + + ret = kvm_call_hyp_nvhe(__pkvm_load_tracing, (unsigned long)desc, desc_size); + if (ret) + goto err_teardown_pages; + + hyp_buffer->remote.pdesc = &desc->page_desc; + hyp_buffer->remote.get_reader_page = __get_reader_page; + hyp_buffer->trace_buffer = ring_buffer_remote(&hyp_buffer->remote); + if (!hyp_buffer->trace_buffer) { + ret = -ENOMEM; + goto err_teardown_tracing; + } + + hyp_buffer->desc = desc; + hyp_buffer->desc_size = desc_size; + + return 0; + +err_teardown_tracing: + kvm_call_hyp_nvhe(__pkvm_teardown_tracing); +err_teardown_pages: + hyp_trace_teardown_pages(desc, INT_MAX); +err_free_backing: + bpage_backing_free(&desc->backing); +err_free_pages: + hyp_trace_free_pages(desc); +err_free_desc: + free_pages_exact(desc, desc_size); + + return ret; +} + +static void hyp_trace_buffer_teardown(struct hyp_trace_buffer *hyp_buffer) +{ + struct hyp_trace_desc *desc = hyp_buffer->desc; + size_t desc_size = hyp_buffer->desc_size; + + if (!hyp_trace_buffer_loaded(hyp_buffer)) + return; + + if (hyp_trace_buffer_used(hyp_buffer)) + return; + + if (kvm_call_hyp_nvhe(__pkvm_teardown_tracing)) + return; + + ring_buffer_free(hyp_buffer->trace_buffer); + hyp_trace_teardown_pages(desc, INT_MAX); + bpage_backing_free(&desc->backing); + hyp_trace_free_pages(desc); + free_pages_exact(desc, desc_size); + hyp_buffer->trace_buffer = NULL; +} + +static int hyp_trace_start(void) +{ + struct hyp_trace_buffer *hyp_buffer = &hyp_trace_buffer; + int ret = 0; + + mutex_lock(&hyp_buffer->lock); + + if (hyp_buffer->tracing_on) + goto out; + + ret = hyp_trace_buffer_load(hyp_buffer, hyp_trace_buffer_size); + if (ret) + goto out; + + ret = kvm_call_hyp_nvhe(__pkvm_enable_tracing, true); + if (ret) { + hyp_trace_buffer_teardown(hyp_buffer); + goto out; + } + + hyp_buffer->tracing_on = true; + +out: + mutex_unlock(&hyp_buffer->lock); + + return ret; +} + +static void hyp_trace_stop(void) +{ + struct hyp_trace_buffer *hyp_buffer = &hyp_trace_buffer; + int ret; + + mutex_lock(&hyp_buffer->lock); + + if (!hyp_buffer->tracing_on) + goto end; + + ret = kvm_call_hyp_nvhe(__pkvm_enable_tracing, false); + if (!ret) { + ring_buffer_poll_remote(hyp_buffer->trace_buffer, + RING_BUFFER_ALL_CPUS); + hyp_buffer->tracing_on = false; + hyp_trace_buffer_teardown(hyp_buffer); + } + +end: + mutex_unlock(&hyp_buffer->lock); +} + +static ssize_t hyp_tracing_on(struct file *filp, const char __user *ubuf, + size_t cnt, loff_t *ppos) +{ + unsigned long val; + int ret; + + ret = kstrtoul_from_user(ubuf, cnt, 10, &val); + if (ret) + return ret; + + if (val) + ret = hyp_trace_start(); + else + hyp_trace_stop(); + + return ret ? ret : cnt; +} + +static ssize_t hyp_tracing_on_read(struct file *filp, char __user *ubuf, + size_t cnt, loff_t *ppos) +{ + char buf[3]; + int r; + + mutex_lock(&hyp_trace_buffer.lock); + r = sprintf(buf, "%d\n", hyp_trace_buffer.tracing_on); + mutex_unlock(&hyp_trace_buffer.lock); + + return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); +} + +static const struct file_operations hyp_tracing_on_fops = { + .write = hyp_tracing_on, + .read = hyp_tracing_on_read, +}; + +static ssize_t hyp_buffer_size(struct file *filp, const char __user *ubuf, + size_t cnt, loff_t *ppos) +{ + unsigned long val; + int ret; + + ret = kstrtoul_from_user(ubuf, cnt, 10, &val); + if (ret) + return ret; + + if (!val) + return -EINVAL; + + mutex_lock(&hyp_trace_buffer.lock); + hyp_trace_buffer_size = val << 10; /* KB to B */ + mutex_unlock(&hyp_trace_buffer.lock); + + return cnt; +} + +static ssize_t hyp_buffer_size_read(struct file *filp, char __user *ubuf, + size_t cnt, loff_t *ppos) +{ + char buf[64]; + int r; + + mutex_lock(&hyp_trace_buffer.lock); + r = sprintf(buf, "%lu (%s)\n", hyp_trace_buffer_size >> 10, + hyp_trace_buffer_loaded(&hyp_trace_buffer) ? + "loaded" : "unloaded"); + mutex_unlock(&hyp_trace_buffer.lock); + + return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); +} + +static const struct file_operations hyp_buffer_size_fops = { + .write = hyp_buffer_size, + .read = hyp_buffer_size_read, +}; + +static void ht_print_trace_time(struct ht_iterator *iter) +{ + unsigned long usecs_rem; + u64 ts_ns = iter->ts; + + do_div(ts_ns, 1000); + usecs_rem = do_div(ts_ns, USEC_PER_SEC); + + trace_seq_printf(&iter->seq, "%5lu.%06lu: ", + (unsigned long)ts_ns, usecs_rem); +} + +static void ht_print_trace_cpu(struct ht_iterator *iter) +{ + trace_seq_printf(&iter->seq, "[%03d]\t", iter->ent_cpu); +} + +static int ht_print_trace_fmt(struct ht_iterator *iter) +{ + if (iter->lost_events) + trace_seq_printf(&iter->seq, "CPU:%d [LOST %lu EVENTS]\n", + iter->ent_cpu, iter->lost_events); + + ht_print_trace_cpu(iter); + ht_print_trace_time(iter); + + return trace_seq_has_overflowed(&iter->seq) ? -EOVERFLOW : 0; +}; + +static struct ring_buffer_event *__ht_next_pipe_event(struct ht_iterator *iter) +{ + struct ring_buffer_event *evt = NULL; + int cpu = iter->cpu; + + if (cpu != RING_BUFFER_ALL_CPUS) { + if (ring_buffer_empty_cpu(iter->trace_buffer, cpu)) + return NULL; + + iter->ent_cpu = cpu; + + return ring_buffer_peek(iter->trace_buffer, cpu, &iter->ts, + &iter->lost_events); + } + + iter->ts = LLONG_MAX; + for_each_possible_cpu(cpu) { + struct ring_buffer_event *_evt; + unsigned long lost_events; + u64 ts; + + if (ring_buffer_empty_cpu(iter->trace_buffer, cpu)) + continue; + + _evt = ring_buffer_peek(iter->trace_buffer, cpu, &ts, + &lost_events); + if (!_evt) + continue; + + if (ts >= iter->ts) + continue; + + iter->ts = ts; + iter->ent_cpu = cpu; + iter->lost_events = lost_events; + evt = _evt; + } + + return evt; +} + +static void *ht_next_pipe_event(struct ht_iterator *iter) +{ + struct ring_buffer_event *event; + + event = __ht_next_pipe_event(iter); + if (!event) + return NULL; + + iter->ent = (struct hyp_entry_hdr *)&event->array[1]; + iter->ent_size = event->array[0]; + + return iter; +} + +static ssize_t +hyp_trace_pipe_read(struct file *file, char __user *ubuf, + size_t cnt, loff_t *ppos) +{ + struct ht_iterator *iter = (struct ht_iterator *)file->private_data; + int ret; + +copy_to_user: + ret = trace_seq_to_user(&iter->seq, ubuf, cnt); + if (ret != -EBUSY) + return ret; + + trace_seq_init(&iter->seq); + + ret = ring_buffer_wait(iter->trace_buffer, iter->cpu, 0, NULL, NULL); + if (ret < 0) + return ret; + + while (ht_next_pipe_event(iter)) { + int prev_len = iter->seq.seq.len; + + if (ht_print_trace_fmt(iter)) { + iter->seq.seq.len = prev_len; + break; + } + + ring_buffer_consume(iter->trace_buffer, iter->ent_cpu, NULL, + NULL); + } + + goto copy_to_user; +} + +static void __poll_remote(struct work_struct *work) +{ + struct delayed_work *dwork = to_delayed_work(work); + struct ht_iterator *iter; + + iter = container_of(dwork, struct ht_iterator, poll_work); + + ring_buffer_poll_remote(iter->trace_buffer, iter->cpu); + + schedule_delayed_work((struct delayed_work *)work, + msecs_to_jiffies(RB_POLL_MS)); +} + +static int hyp_trace_pipe_open(struct inode *inode, struct file *file) +{ + struct hyp_trace_buffer *hyp_buffer = &hyp_trace_buffer; + int cpu = (s64)inode->i_private; + struct ht_iterator *iter = NULL; + int ret; + + mutex_lock(&hyp_buffer->lock); + + if (hyp_buffer->nr_readers == INT_MAX) { + ret = -EBUSY; + goto unlock; + } + + ret = hyp_trace_buffer_load(hyp_buffer, hyp_trace_buffer_size); + if (ret) + goto unlock; + + iter = kzalloc(sizeof(*iter), GFP_KERNEL); + if (!iter) { + ret = -ENOMEM; + goto unlock; + } + iter->trace_buffer = hyp_buffer->trace_buffer; + iter->cpu = cpu; + trace_seq_init(&iter->seq); + file->private_data = iter; + + ret = ring_buffer_poll_remote(hyp_buffer->trace_buffer, cpu); + if (ret) + goto unlock; + + INIT_DELAYED_WORK(&iter->poll_work, __poll_remote); + schedule_delayed_work(&iter->poll_work, msecs_to_jiffies(RB_POLL_MS)); + + hyp_buffer->nr_readers++; + +unlock: + if (ret) { + hyp_trace_buffer_teardown(hyp_buffer); + kfree(iter); + } + + mutex_unlock(&hyp_buffer->lock); + + return ret; +} + +static int hyp_trace_pipe_release(struct inode *inode, struct file *file) +{ + struct hyp_trace_buffer *hyp_buffer = &hyp_trace_buffer; + struct ht_iterator *iter = file->private_data; + + cancel_delayed_work_sync(&iter->poll_work); + + mutex_lock(&hyp_buffer->lock); + + WARN_ON(--hyp_buffer->nr_readers < 0); + + hyp_trace_buffer_teardown(hyp_buffer); + + mutex_unlock(&hyp_buffer->lock); + + kfree(iter); + + return 0; +} + +static const struct file_operations hyp_trace_pipe_fops = { + .open = hyp_trace_pipe_open, + .read = hyp_trace_pipe_read, + .release = hyp_trace_pipe_release, +}; + +int hyp_trace_init_tracefs(void) +{ + struct dentry *root, *per_cpu_root; + char per_cpu_name[16]; + long cpu; + + if (!is_protected_kvm_enabled()) + return 0; + + root = tracefs_create_dir(TRACEFS_DIR, NULL); + if (!root) { + pr_err("Failed to create tracefs "TRACEFS_DIR"/\n"); + return -ENODEV; + } + + tracefs_create_file("tracing_on", TRACEFS_MODE_WRITE, root, NULL, + &hyp_tracing_on_fops); + + tracefs_create_file("buffer_size_kb", TRACEFS_MODE_WRITE, root, NULL, + &hyp_buffer_size_fops); + + tracefs_create_file("trace_pipe", TRACEFS_MODE_WRITE, root, + (void *)RING_BUFFER_ALL_CPUS, &hyp_trace_pipe_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"); + return -ENODEV; + } + + for_each_possible_cpu(cpu) { + struct dentry *per_cpu_dir; + + snprintf(per_cpu_name, sizeof(per_cpu_name), "cpu%ld", cpu); + per_cpu_dir = tracefs_create_dir(per_cpu_name, per_cpu_root); + if (!per_cpu_dir) { + pr_warn("Failed to create tracefs "TRACEFS_DIR"/per_cpu/cpu%ld\n", + cpu); + continue; + } + + tracefs_create_file("trace_pipe", TRACEFS_MODE_READ, per_cpu_dir, + (void *)cpu, &hyp_trace_pipe_fops); + } + + return 0; +} diff --git a/arch/arm64/kvm/hyp_trace.h b/arch/arm64/kvm/hyp_trace.h new file mode 100644 index 000000000000..14fc06c625a6 --- /dev/null +++ b/arch/arm64/kvm/hyp_trace.h @@ -0,0 +1,28 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef __ARM64_KVM_HYP_TRACE_H__ +#define __ARM64_KVM_HYP_TRACE_H__ + +#include <linux/trace_seq.h> +#include <linux/workqueue.h> + +struct ht_iterator { + struct trace_buffer *trace_buffer; + int cpu; + struct hyp_entry_hdr *ent; + unsigned long lost_events; + int ent_cpu; + size_t ent_size; + u64 ts; + void *spare; + size_t copy_leftover; + struct trace_seq seq; + struct delayed_work poll_work; +}; + +#ifdef CONFIG_TRACING +int hyp_trace_init_tracefs(void); +#else +static inline int hyp_trace_init_tracefs(void) { return 0; } +#endif +#endif -- 2.47.1.613.gc27f4b7a9f-goog
