+Mark
On 10/01/17 11:38, Punit Agrawal wrote:
> Both AArch32 and AArch64 mode of the ARMv8 architecture support trapping
> certain VM operations, e.g, TLB and cache maintenance
> operations. Selective trapping of these operations for specific VMs can
> be used to track the frequency with which these occur during execution.
>
> Add a software PMU on the host that can support tracking VM
> operations (in the form of PMU events). Supporting new events requires
> providing callbacks to configure the VM to enable/disable the trapping
> and read a count of the frequency.
>
> The host PMU events can be controlled by tools like perf that use
> standard kernel perf interfaces.
>
> Signed-off-by: Punit Agrawal <punit.agrawal@xxxxxxx>
> Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> ---
> arch/arm/include/asm/kvm_host.h | 8 ++
> arch/arm/kvm/arm.c | 2 +
> arch/arm64/include/asm/kvm_host.h | 8 ++
> virt/kvm/arm/host_pmu.c | 272 ++++++++++++++++++++++++++++++++++++++
> 4 files changed, 290 insertions(+)
> create mode 100644 virt/kvm/arm/host_pmu.c
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 26f0c8a0b790..b988f8801b86 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -289,6 +289,14 @@ static inline int kvm_arch_dev_ioctl_check_extension(struct kvm *kvm, long ext)
> int kvm_perf_init(void);
> int kvm_perf_teardown(void);
>
> +#if !defined(CONFIG_KVM_HOST_PMU)
> +static inline int kvm_host_pmu_init(void) { return 0; }
> +static inline void kvm_host_pmu_teardown(void) { }
> +#else
> +int kvm_host_pmu_init(void);
> +void kvm_host_pmu_teardown(void);
> +#endif
> +
> void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
>
> struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 11676787ad49..058626b65b8d 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -1263,6 +1263,7 @@ static int init_subsystems(void)
> goto out;
>
> kvm_perf_init();
> + kvm_host_pmu_init();
> kvm_coproc_table_init();
>
> out:
> @@ -1453,6 +1454,7 @@ int kvm_arch_init(void *opaque)
> void kvm_arch_exit(void)
> {
> kvm_perf_teardown();
> + kvm_host_pmu_teardown();
> }
>
> static int arm_init(void)
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 1e83b707f14c..018f887e8964 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -349,6 +349,14 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
> int kvm_perf_init(void);
> int kvm_perf_teardown(void);
>
> +#if !defined(CONFIG_KVM_HOST_PMU)
> +static inline int kvm_host_pmu_init(void) { return 0; }
> +static inline void kvm_host_pmu_teardown(void) { }
> +#else
> +int kvm_host_pmu_init(void);
> +void kvm_host_pmu_teardown(void);
> +#endif
> +
> struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
>
> static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr,
> diff --git a/virt/kvm/arm/host_pmu.c b/virt/kvm/arm/host_pmu.c
> new file mode 100644
> index 000000000000..fc610ccc169a
> --- /dev/null
> +++ b/virt/kvm/arm/host_pmu.c
> @@ -0,0 +1,272 @@
> +#include <linux/cpumask.h>
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/kvm_host.h>
> +#include <linux/list.h>
> +#include <linux/perf_event.h>
> +#include <linux/pid.h>
> +#include <linux/sched.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock_types.h>
> +#include <linux/sysfs.h>
> +
> +#include <asm/kvm_emulate.h>
> +
> +enum host_pmu_events {
> + KVM_HOST_MAX_EVENTS,
> +};
> +
> +struct host_pmu {
> + struct pmu pmu;
> + spinlock_t event_list_lock;
> + struct list_head event_list_head;
> +} host_pmu;
> +#define to_host_pmu(p) (container_of(p, struct host_pmu, pmu))
> +
> +typedef void (*configure_event_fn)(struct kvm *kvm, bool enable);
> +typedef u64 (*get_event_count_fn)(struct kvm *kvm);
> +
> +struct kvm_event_cb {
> + enum host_pmu_events event;
> + get_event_count_fn get_event_count;
> + configure_event_fn configure_event;
> +};
> +
> +struct event_data {
> + bool enable;
> + struct kvm *kvm;
> + struct kvm_event_cb *cb;
> + struct work_struct work;
> + struct list_head event_list;
> +};
> +
> +static struct kvm_event_cb event_callbacks[] = {
> +};
> +
> +static struct attribute *event_attrs[] = {
> + NULL,
> +};
> +
> +static struct attribute_group events_attr_group = {
> + .name = "events",
> + .attrs = event_attrs,
> +};
> +
> +
> +#define VM_MASK GENMASK_ULL(31, 0)
> +#define EVENT_MASK GENMASK_ULL(32, 39)
> +#define EVENT_SHIFT (32)
> +
> +#define to_pid(cfg) ((cfg) & VM_MASK)
> +#define to_event(cfg) (((cfg) & EVENT_MASK) >> EVENT_SHIFT)
> +
> +PMU_FORMAT_ATTR(vm, "config:0-31");
> +PMU_FORMAT_ATTR(event, "config:32-39");
I'm a bit confused by these. Can't you get the PID of the VM you're
tracing directly from perf, without having to encode things? And if you
can't, surely this should be a function of the size of pid_t?
Mark, can you shine some light here?
> +
> +static struct attribute *format_attrs[] = {
> + &format_attr_vm.attr,
> + &format_attr_event.attr,
> + NULL,
> +};
> +
> +static struct attribute_group format_attr_group = {
> + .name = "format",
> + .attrs = format_attrs,
> +};
> +
> +static const struct attribute_group *attr_groups[] = {
> + &events_attr_group,
> + &format_attr_group,
> + NULL,
> +};
> +
> +static void host_event_destroy(struct perf_event *event)
> +{
> + struct host_pmu *host_pmu = to_host_pmu(event->pmu);
> + struct event_data *e_data = event->pmu_private;
> +
> + /*
> + * Ensure outstanding work items related to this event are
> + * completed before freeing resources.
> + */
> + flush_work(&e_data->work);
> +
> + kvm_put_kvm(e_data->kvm);
> +
> + spin_lock(&host_pmu->event_list_lock);
> + list_del(&e_data->event_list);
> + spin_unlock(&host_pmu->event_list_lock);
> + kfree(e_data);
> +}
> +
> +void host_event_work(struct work_struct *work)
> +{
> + struct event_data *e_data = container_of(work, struct event_data, work);
> + struct kvm *kvm = e_data->kvm;
> +
> + e_data->cb->configure_event(kvm, e_data->enable);
> +}
> +
> +static int host_event_init(struct perf_event *event)
> +{
> + struct host_pmu *host_pmu = to_host_pmu(event->pmu);
> + int event_id = to_event(event->attr.config);
> + pid_t task_pid = to_pid(event->attr.config);
> + struct event_data *e_data, *pos;
> + bool found = false;
> + struct pid *pid;
> + struct kvm *kvm;
> + int ret = 0;
> +
> + if (event->attr.type != event->pmu->type)
> + return -ENOENT;
> +
> + if (has_branch_stack(event) ||
> + is_sampling_event(event) ||
> + event->attr.exclude_user ||
> + event->attr.exclude_kernel ||
> + event->attr.exclude_hv ||
> + event->attr.exclude_idle ||
> + event->attr.exclude_guest) {
> + return -EINVAL;
> + }
> +
> + if (event->attach_state == PERF_ATTACH_TASK)
> + return -EOPNOTSUPP;
> +
> + if (event->cpu < 0)
> + return -EINVAL;
> +
> + if (event_id >= KVM_HOST_MAX_EVENTS)
> + return -EINVAL;
> +
> + pid = find_get_pid(task_pid);
> + spin_lock(&kvm_lock);
> + list_for_each_entry(kvm, &vm_list, vm_list) {
> + if (kvm->pid == pid) {
> + kvm_get_kvm(kvm);
> + found = true;
> + break;
> + }
> + }
> + spin_unlock(&kvm_lock);
> + put_pid(pid);
> +
> + if (!found)
> + return -EINVAL;
> +
> + spin_lock(&host_pmu->event_list_lock);
> + /* Make sure we don't already have the (event_id, kvm) pair */
> + list_for_each_entry(pos, &host_pmu->event_list_head, event_list) {
> + if (pos->cb->event == event_id &&
> + pos->kvm->pid == pid) {
> + kvm_put_kvm(kvm);
> + ret = -EOPNOTSUPP;
> + goto unlock;
> + }
> + }
> +
> + e_data = kzalloc(sizeof(*e_data), GFP_KERNEL);
> + e_data->kvm = kvm;
> + e_data->cb = &event_callbacks[event_id];
> + INIT_WORK(&e_data->work, host_event_work);
> + event->pmu_private = e_data;
> + event->cpu = cpumask_first(cpu_online_mask);
> + event->destroy = host_event_destroy;
> +
> + list_add_tail(&e_data->event_list, &host_pmu->event_list_head);
> +
> +unlock:
> + spin_unlock(&host_pmu->event_list_lock);
> +
> + return ret;
> +}
> +
> +static void host_event_update(struct perf_event *event)
> +{
> + struct event_data *e_data = event->pmu_private;
> + struct kvm_event_cb *cb = e_data->cb;
> + struct kvm *kvm = e_data->kvm;
> + struct hw_perf_event *hw = &event->hw;
> + u64 prev_count, new_count;
> +
> + do {
> + prev_count = local64_read(&hw->prev_count);
> + new_count = cb->get_event_count(kvm);
> + } while (local64_xchg(&hw->prev_count, new_count) != prev_count);
> +
> + local64_add(new_count - prev_count, &event->count);
> +}
> +
> +static void host_event_start(struct perf_event *event, int flags)
> +{
> + struct event_data *e_data = event->pmu_private;
> + struct kvm_event_cb *cb = e_data->cb;
> + struct kvm *kvm = e_data->kvm;
> + u64 val;
> +
> + val = cb->get_event_count(kvm);
> + local64_set(&event->hw.prev_count, val);
> +
> + e_data->enable = true;
> + schedule_work(&e_data->work);
> +}
> +
> +static void host_event_stop(struct perf_event *event, int flags)
> +{
> + struct event_data *e_data = event->pmu_private;
> +
> + e_data->enable = false;
> + schedule_work(&e_data->work);
> +
> + if (flags & PERF_EF_UPDATE)
> + host_event_update(event);
> +}
> +
> +static int host_event_add(struct perf_event *event, int flags)
> +{
> + if (flags & PERF_EF_START)
> + host_event_start(event, flags);
> +
> + return 0;
> +}
> +
> +static void host_event_del(struct perf_event *event, int flags)
> +{
> + host_event_stop(event, PERF_EF_UPDATE);
> +}
> +
> +static void host_event_read(struct perf_event *event)
> +{
> + host_event_update(event);
> +}
> +
> +static void init_host_pmu(struct host_pmu *host_pmu)
> +{
> + host_pmu->pmu = (struct pmu) {
> + .task_ctx_nr = perf_sw_context,
> + .attr_groups = attr_groups,
> + .event_init = host_event_init,
> + .add = host_event_add,
> + .del = host_event_del,
> + .start = host_event_start,
> + .stop = host_event_stop,
> + .read = host_event_read,
> + .capabilities = PERF_PMU_CAP_NO_INTERRUPT,
> + };
> +
> + INIT_LIST_HEAD(&host_pmu->event_list_head);
> + spin_lock_init(&host_pmu->event_list_lock);
> +}
> +
> +int kvm_host_pmu_init(void)
> +{
> + init_host_pmu(&host_pmu);
> +
> + return perf_pmu_register(&host_pmu.pmu, "kvm", -1);
> +}
> +
> +void kvm_host_pmu_teardown(void)
> +{
> + perf_pmu_unregister(&host_pmu.pmu);
> +}
>
This patch really makes me think that there is nothing arm-specific in
here at all. Why can't it be a generic feature through which
architectures can expose events in a generic way (or as close as
possible to being generic)?
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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