On 11.12.2024 16:50, Lukas Zapolskas wrote:
> To allow for combining the requests from multiple userspace clients, an
> intermediary layer between the HW/FW interfaces and userspace is
> created, containing the information for the counter requests and
> tracking of insert and extract indices. Each session starts inactive and
> must be explicitly activated via PERF_CONTROL.START, and explicitly
> stopped via PERF_CONTROL.STOP. Userspace identifies a single client with
> its session ID and the panthor file it is associated with.
>
> The SAMPLE and STOP commands both produce a single sample when called,
> and these samples can be disambiguated via the opaque user data field
> passed in the PERF_CONTROL uAPI. If this functionality is not desired,
> these fields can be kept as zero, as the kernel copies this value into
> the corresponding sample without attempting to interpret it.
>
> Currently, only manual sampling sessions are supported, providing
> samples when userspace calls PERF_CONTROL.SAMPLE, and only a single
> session is allowed at a time. Multiple sessions and periodic sampling
> will be enabled in following patches.
>
> No protected is provided against the 32-bit hardware counter overflows,
Spelling: protected
> so for the moment it is up to userspace to ensure that the counters are
> sampled at a reasonable frequency.
> The counter set enum is added to the uapi to clarify the restrictions on
> calling the interface.
>
> Signed-off-by: Lukas Zapolskas <lukas.zapolskas@xxxxxxx>
> ---
> drivers/gpu/drm/panthor/panthor_device.h | 3 +
> drivers/gpu/drm/panthor/panthor_drv.c | 1 +
> drivers/gpu/drm/panthor/panthor_perf.c | 697 ++++++++++++++++++++++-
> include/uapi/drm/panthor_drm.h | 50 +-
> 4 files changed, 732 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index aca33d03036c..9ed1e9aed521 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -210,6 +210,9 @@ struct panthor_file {
> /** @ptdev: Device attached to this file. */
> struct panthor_device *ptdev;
>
> + /** @drm_file: Corresponding drm_file */
> + struct drm_file *drm_file;
I think you could do away with this member, wrote more about this below.
> /** @vms: VM pool attached to this file. */
> struct panthor_vm_pool *vms;
>
> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> index 458175f58b15..2848ab442d10 100644
> --- a/drivers/gpu/drm/panthor/panthor_drv.c
> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> @@ -1505,6 +1505,7 @@ panthor_open(struct drm_device *ddev, struct drm_file *file)
> }
>
> pfile->ptdev = ptdev;
> + pfile->drm_file = file;
Same as above, feel like this is not necessary.
>
> ret = panthor_vm_pool_create(pfile);
> if (ret)
> diff --git a/drivers/gpu/drm/panthor/panthor_perf.c b/drivers/gpu/drm/panthor/panthor_perf.c
> index 6498279ec036..42d8b6f8c45d 100644
> --- a/drivers/gpu/drm/panthor/panthor_perf.c
> +++ b/drivers/gpu/drm/panthor/panthor_perf.c
> @@ -3,16 +3,162 @@
> /* Copyright 2024 Arm ltd. */
>
> #include <drm/drm_file.h>
> +#include <drm/drm_gem.h>
> #include <drm/drm_gem_shmem_helper.h>
> #include <drm/drm_managed.h>
> +#include <drm/drm_print.h>
> #include <drm/panthor_drm.h>
>
> +#include <linux/circ_buf.h>
> +#include <linux/iosys-map.h>
> +#include <linux/pm_runtime.h>
> +
> #include "panthor_device.h"
> #include "panthor_fw.h"
> #include "panthor_gpu.h"
> #include "panthor_perf.h"
> #include "panthor_regs.h"
>
> +/**
> + * PANTHOR_PERF_EM_BITS - Number of bits in a user-facing enable mask. This must correspond
> + * to the maximum number of counters available for selection on the newest
> + * Mali GPUs (128 as of the Mali-Gx15).
> + */
> +#define PANTHOR_PERF_EM_BITS (BITS_PER_TYPE(u64) * 2)
> +
> +/**
> + * enum panthor_perf_session_state - Session state bits.
> + */
> +enum panthor_perf_session_state {
> + /** @PANTHOR_PERF_SESSION_ACTIVE: The session is active and can be used for sampling. */
> + PANTHOR_PERF_SESSION_ACTIVE = 0,
> +
> + /**
> + * @PANTHOR_PERF_SESSION_OVERFLOW: The session encountered an overflow in one of the
> + * counters during the last sampling period. This flag
> + * gets propagated as part of samples emitted for this
> + * session, to ensure the userspace client can gracefully
> + * handle this data corruption.
> + */
How would a client normally deal with data corruption in a sample?
> + PANTHOR_PERF_SESSION_OVERFLOW,
> +
> + /** @PANTHOR_PERF_SESSION_MAX: Bits needed to represent the state. Must be last.*/
> + PANTHOR_PERF_SESSION_MAX,
> +};
> +
> +struct panthor_perf_enable_masks {
> + /**
> + * @link: List node used to keep track of the enable masks aggregated by the sampler.
> + */
> + struct list_head link;
> +
> + /** @refs: Number of references taken out on an instantiated enable mask. */
> + struct kref refs;
> +
> + /**
> + * @mask: Array of bitmasks indicating the counters userspace requested, where
> + * one bit represents a single counter. Used to build the firmware configuration
> + * and ensure that userspace clients obtain only the counters they requested.
> + */
> + DECLARE_BITMAP(mask, PANTHOR_PERF_EM_BITS)[DRM_PANTHOR_PERF_BLOCK_MAX];
> +};
> +
> +struct panthor_perf_counter_block {
> + struct drm_panthor_perf_block_header header;
> + u64 counters[];
> +};
I think I remember reading in the spec thata block header was 12 bytes in length
but the one defined here seems to have many more fields.
> +struct panthor_perf_session {
> + DECLARE_BITMAP(state, PANTHOR_PERF_SESSION_MAX);
I'm wondering, because I don't remember having seen this pattern before.
Is it common in kernel code to declare bitmaps for masks of enum values in this way?
> + /**
> + * @user_sample_size: The size of a single sample as exposed to userspace. For the sake of
> + * simplicity, the current implementation exposes the same structure
> + * as provided by firmware, after annotating the sample and the blocks,
> + * and zero-extending the counters themselves (to account for in-kernel
> + * accumulation).
> + *
> + * This may also allow further memory-optimizations of compressing the
> + * sample to provide only requested blocks, if deemed to be worth the
> + * additional complexity.
> + */
> + size_t user_sample_size;
> +
> + /**
> + * @sample_freq_ns: Period between subsequent sample requests. Zero indicates that
> + * userspace will be responsible for requesting samples.
> + */
> + u64 sample_freq_ns;
> +
> + /** @sample_start_ns: Sample request time, obtained from a monotonic raw clock. */
> + u64 sample_start_ns;
> +
> + /**
> + * @user_data: Opaque handle passed in when starting a session, requesting a sample (for
> + * manual sampling sessions only) and when stopping a session. This handle
> + * allows the disambiguation of a sample in the ringbuffer.
> + */
> + u64 user_data;
> +
> + /**
> + * @eventfd: Event file descriptor context used to signal userspace of a new sample
> + * being emitted.
> + */
> + struct eventfd_ctx *eventfd;
> +
> + /**
> + * @enabled_counters: This session's requested counters. Note that these cannot change
> + * for the lifetime of the session.
> + */
> + struct panthor_perf_enable_masks *enabled_counters;
It seems the enable mask for a session is tied to the session's lifetime. In
panthor_perf_session_setup(), you create one and then increase its reference
count from within panthor_perf_sampler_add(), which is not being called from
anywhere else. Maybe in that case you could do without the reference count and
have a non-pointer struct panthor_perf_enable_masks member here?
> + /** @ringbuf_slots: Slots in the user-facing ringbuffer. */
> + size_t ringbuf_slots;
> +
> + /** @ring_buf: BO for the userspace ringbuffer. */
> + struct drm_gem_object *ring_buf;
> +
> + /**
> + * @control_buf: BO for the insert and extract indices.
> + */
> + struct drm_gem_object *control_buf;
> +
> + /**
> + * @extract_idx: The extract index is used by userspace to indicate the position of the
> + * consumer in the ringbuffer.
> + */
> + u32 *extract_idx;
> +
> + /**
> + * @insert_idx: The insert index is used by the kernel to indicate the position of the
> + * latest sample exposed to userspace.
> + */
> + u32 *insert_idx;
> +
> + /** @samples: The mapping of the @ring_buf into the kernel's VA space. */
> + u8 *samples;
> +
> + /**
> + * @waiting: The list node used by the sampler to track the sessions waiting for a sample.
> + */
> + struct list_head waiting;
> +
> + /**
> + * @pfile: The panthor file which was used to create a session, used for the postclose
> + * handling and to prevent a misconfigured userspace from closing unrelated
> + * sessions.
> + */
> + struct panthor_file *pfile;
> +
> + /**
> + * @ref: Session reference count. The sample delivery to userspace is asynchronous, meaning
> + * the lifetime of the session must extend at least until the sample is exposed to
> + * userspace.
> + */
> + struct kref ref;
> +};
> +
> +
> struct panthor_perf {
> /**
> * @block_set: The global counter set configured onto the HW.
> @@ -63,39 +209,154 @@ void panthor_perf_info_init(struct panthor_device *ptdev)
> perf_info->shader_blocks = hweight64(ptdev->gpu_info.shader_present);
> }
>
> -int panthor_perf_session_setup(struct panthor_device *ptdev, struct panthor_perf *perf,
> - struct drm_panthor_perf_cmd_setup *setup_args,
> - struct panthor_file *pfile)
> +static struct panthor_perf_enable_masks *panthor_perf_em_new(void)
> {
> - return -EOPNOTSUPP;
> + struct panthor_perf_enable_masks *em = kmalloc(sizeof(*em), GFP_KERNEL);
> +
> + if (!em)
> + return ERR_PTR(-ENOMEM);
> +
> + INIT_LIST_HEAD(&em->link);
> +
> + kref_init(&em->refs);
> +
> + return em;
> }
>
> -int panthor_perf_session_teardown(struct panthor_file *pfile, struct panthor_perf *perf,
> - u32 sid)
> +static struct panthor_perf_enable_masks *panthor_perf_create_em(struct drm_panthor_perf_cmd_setup
> + *setup_args)
> {
> - return -EOPNOTSUPP;
> + struct panthor_perf_enable_masks *em = panthor_perf_em_new();
> +
> + if (IS_ERR_OR_NULL(em))
> + return em;
> +
> + bitmap_from_arr64(em->mask[DRM_PANTHOR_PERF_BLOCK_FW],
> + setup_args->fw_enable_mask, PANTHOR_PERF_EM_BITS);
> + bitmap_from_arr64(em->mask[DRM_PANTHOR_PERF_BLOCK_CSG],
> + setup_args->csg_enable_mask, PANTHOR_PERF_EM_BITS);
> + bitmap_from_arr64(em->mask[DRM_PANTHOR_PERF_BLOCK_CSHW],
> + setup_args->cshw_enable_mask, PANTHOR_PERF_EM_BITS);
> + bitmap_from_arr64(em->mask[DRM_PANTHOR_PERF_BLOCK_TILER],
> + setup_args->tiler_enable_mask, PANTHOR_PERF_EM_BITS);
> + bitmap_from_arr64(em->mask[DRM_PANTHOR_PERF_BLOCK_MEMSYS],
> + setup_args->memsys_enable_mask, PANTHOR_PERF_EM_BITS);
> + bitmap_from_arr64(em->mask[DRM_PANTHOR_PERF_BLOCK_SHADER],
> + setup_args->shader_enable_mask, PANTHOR_PERF_EM_BITS);
To save some repetition, maybe do this, although it might depend on uAPI
structures being arranged in the right way, and the compiler not inserting
unusual padding between consecutive members:
unsigned int block; u64 *mask;
for (mask = &setup_args->fw_enable_mask[0], block = DRM_PANTHOR_PERF_BLOCK_FW;
block < DRM_PANTHOR_PERF_BLOCK_LAST; block++, mask += 2)
bitmap_from_arr64(em->mask[block], mask, PANTHOR_PERF_EM_BITS);
> + return em;
> }
>
> -int panthor_perf_session_start(struct panthor_file *pfile, struct panthor_perf *perf,
> - u32 sid, u64 user_data)
> +static void panthor_perf_destroy_em_kref(struct kref *em_kref)
> {
> - return -EOPNOTSUPP;
> + struct panthor_perf_enable_masks *em = container_of(em_kref, typeof(*em), refs);
> +
> + if (!list_empty(&em->link))
> + return;
Could this lead to a situation where the enable mask's refcnt reaches 0,
but because it hadn't yet been removed from the session's list, the
mask object is never freed?
> + kfree(em);
> }
>
> -int panthor_perf_session_stop(struct panthor_file *pfile, struct panthor_perf *perf,
> - u32 sid, u64 user_data)
> +static size_t get_annotated_block_size(size_t counters_per_block)
> {
> - return -EOPNOTSUPP;
> + return struct_size_t(struct panthor_perf_counter_block, counters, counters_per_block);
> }
>
> -int panthor_perf_session_sample(struct panthor_file *pfile, struct panthor_perf *perf,
> - u32 sid, u64 user_data)
> +static u32 session_read_extract_idx(struct panthor_perf_session *session)
> +{
> + /* Userspace will update their own extract index to indicate that a sample is consumed
> + * from the ringbuffer, and we must ensure we read the latest value.
> + */
> + return smp_load_acquire(session->extract_idx);
> +}
> +
> +static u32 session_read_insert_idx(struct panthor_perf_session *session)
> +{
> + return *session->insert_idx;
> +}
> +
> +static void session_get(struct panthor_perf_session *session)
> +{
> + kref_get(&session->ref);
> +}
> +
> +static void session_free(struct kref *ref)
> +{
> + struct panthor_perf_session *session = container_of(ref, typeof(*session), ref);
> +
> + if (session->samples) {
> + struct iosys_map map = IOSYS_MAP_INIT_VADDR(session->samples);
> +
> + drm_gem_vunmap_unlocked(session->ring_buf, &map);
> + drm_gem_object_put(session->ring_buf);
> + }
> +
> + if (session->insert_idx && session->extract_idx) {
I think none of these could ever be NULLif session setup succeeded.
> + struct iosys_map map = IOSYS_MAP_INIT_VADDR(session->extract_idx);
> +
> + drm_gem_vunmap_unlocked(session->control_buf, &map);
> + drm_gem_object_put(session->control_buf);
> + }
> +
> + kref_put(&session->enabled_counters->refs, panthor_perf_destroy_em_kref);
> + eventfd_ctx_put(session->eventfd);
> +
> + devm_kfree(session->pfile->ptdev->base.dev, session);
What is the point of using devm allocations in this case, if we always free
the session manually?
> +}
> +
> +static void session_put(struct panthor_perf_session *session)
> +{
> + kref_put(&session->ref, session_free);
> +}
> +
> +/**
> + * session_find - Find a session associated with the given session ID and
> + * panthor_file.
> + * @pfile: Panthor file.
> + * @perf: Panthor perf.
> + * @sid: Session ID.
> + *
> + * The reference count of a valid session is increased to ensure it does not disappear
> + * in the window between the XA lock being dropped and the internal session functions
> + * being called.
> + *
> + * Return: valid session pointer or an ERR_PTR.
> + */
> +static struct panthor_perf_session *session_find(struct panthor_file *pfile,
> + struct panthor_perf *perf, u32 sid)
> {
> - return -EOPNOTSUPP;
> + struct panthor_perf_session *session;
>
> + if (!perf)
> + return ERR_PTR(-EINVAL);
> +
> + xa_lock(&perf->sessions);
> + session = xa_load(&perf->sessions, sid);
> +
> + if (!session || xa_is_err(session)) {
> + xa_unlock(&perf->sessions);
> + return ERR_PTR(-EBADF);
I think we should return NULL in case !session holds true, for panthor_perf_session_start to catch it and return -EINVAL.
> + }
> +
> + if (session->pfile != pfile) {
> + xa_unlock(&perf->sessions);
> + return ERR_PTR(-EINVAL);
> + }
> +
> + session_get(session);
> + xa_unlock(&perf->sessions);
> +
> + return session;
> }
>
> -void panthor_perf_session_destroy(struct panthor_file *pfile, struct panthor_perf *perf) { }
> +static size_t session_get_max_sample_size(const struct drm_panthor_perf_info *const info)
Since this seems to be the size of the sample given to UM, maybe renaming it to
contain _user_ would make its purpose more apparent.
> +{
> + const size_t block_size = get_annotated_block_size(info->counters_per_block);
> + const size_t block_nr = info->cshw_blocks + info->csg_blocks + info->fw_blocks +
> + info->tiler_blocks + info->memsys_blocks + info->shader_blocks;
> +
> + return sizeof(struct drm_panthor_perf_sample_header) + (block_size * block_nr);
> +}
>
> /**
> * panthor_perf_init - Initialize the performance counter subsystem.
> @@ -130,6 +391,399 @@ int panthor_perf_init(struct panthor_device *ptdev)
> ptdev->perf = perf;
>
> return 0;
> +
> +}
> +
> +static int session_validate_set(u8 set)
> +{
> + if (set > DRM_PANTHOR_PERF_SET_TERTIARY)
> + return -EINVAL;
> +
> + if (set == DRM_PANTHOR_PERF_SET_PRIMARY)
> + return 0;
> +
> + if (set > DRM_PANTHOR_PERF_SET_PRIMARY)
> + return capable(CAP_PERFMON) ? 0 : -EACCES;
I'm a bit clueless about the capability API, so I don't quite understand how
this is the way whe decide whether a counter set is legal.
> + return -EINVAL;
> +}
> +
> +/**
> + * panthor_perf_session_setup - Create a user-visible session.
> + *
> + * @ptdev: Handle to the panthor device.
> + * @perf: Handle to the perf control structure.
> + * @setup_args: Setup arguments passed in via ioctl.
> + * @pfile: Panthor file associated with the request.
> + *
> + * Creates a new session associated with the session ID returned. When initialized, the
> + * session must explicitly request sampling to start with a successive call to PERF_CONTROL.START.
> + *
> + * Return: non-negative session identifier on success or negative error code on failure.
> + */
> +int panthor_perf_session_setup(struct panthor_device *ptdev, struct panthor_perf *perf,
> + struct drm_panthor_perf_cmd_setup *setup_args,
> + struct panthor_file *pfile)
> +{
> + struct panthor_perf_session *session;
> + struct drm_gem_object *ringbuffer;
> + struct drm_gem_object *control;
> + const size_t slots = setup_args->sample_slots;
> + struct panthor_perf_enable_masks *em;
> + struct iosys_map rb_map, ctrl_map;
> + size_t user_sample_size;
> + int session_id;
> + int ret;
> +
> + ret = session_validate_set(setup_args->block_set);
> + if (ret)
> + return ret;
> +
> + session = devm_kzalloc(ptdev->base.dev, sizeof(*session), GFP_KERNEL);
> + if (ZERO_OR_NULL_PTR(session))
> + return -ENOMEM;
> +
> + ringbuffer = drm_gem_object_lookup(pfile->drm_file, setup_args->ringbuf_handle);
> + if (!ringbuffer) {
> + ret = -EINVAL;
> + goto cleanup_session;
> + }
I guess this would never be the same ringbuffer we created in
panthor_perf_sampler_init(). I don't think it can be, because that one was is
created as a kernel bo, and has no public facing GEM handler. But then this
means we're doing a copy between the FW ringbuffer and the user-supplied
one. However, I remember from past conversations that the goal of a new
implementation was to avoid doing many perfcnt sample copies between the kernel
and UM, because that would require a huge bandwith when the sample period is
small.
> + control = drm_gem_object_lookup(pfile->drm_file, setup_args->control_handle);
> + if (!control) {
> + ret = -EINVAL;
> + goto cleanup_ringbuf;
> + }
> +
> + user_sample_size = session_get_max_sample_size(&ptdev->perf_info) * slots;
> +
> + if (ringbuffer->size != PFN_ALIGN(user_sample_size)) {
> + ret = -ENOMEM;
> + goto cleanup_control;
> + }
How is information about the max sample size given to UM? I guess through the
values returned through the getparam ioctl(), specifically sample_header_size
and block_header_size?
> + ret = drm_gem_vmap_unlocked(ringbuffer, &rb_map);
> + if (ret)
> + goto cleanup_control;
> +
> +
> + ret = drm_gem_vmap_unlocked(control, &ctrl_map);
> + if (ret)
> + goto cleanup_ring_map;
> +
> + session->eventfd = eventfd_ctx_fdget(setup_args->fd);
> + if (IS_ERR_OR_NULL(session->eventfd)) {
> + ret = PTR_ERR_OR_ZERO(session->eventfd) ?: -EINVAL;
> + goto cleanup_control_map;
> + }
I think eventfd_ctx_fdget can only return error values, so there's no need to
check for NULL or ZERO.
> + em = panthor_perf_create_em(setup_args);
> + if (IS_ERR_OR_NULL(em)) {
> + ret = -ENOMEM;
> + goto cleanup_eventfd;
> + }
> +
> + INIT_LIST_HEAD(&session->waiting);
> + session->extract_idx = ctrl_map.vaddr;
> + *session->extract_idx = 0;
> + session->insert_idx = session->extract_idx + 1;
> + *session->insert_idx = 0;
> +
> + session->samples = rb_map.vaddr;
I think you might've forgotten this:
session->ringbuf_slots = slots;
> + /* TODO This will need validation when we support periodic sampling sessions */
> + if (setup_args->sample_freq_ns) {
> + ret = -EOPNOTSUPP;
> + goto cleanup_em;
> + }
> +
> + session->sample_freq_ns = setup_args->sample_freq_ns;
> + session->user_sample_size = user_sample_size;
> + session->enabled_counters = em;
> + session->ring_buf = ringbuffer;
> + session->control_buf = control;
> + session->pfile = pfile;
> +
> + ret = xa_alloc_cyclic(&perf->sessions, &session_id, session, perf->session_range,
> + &perf->next_session, GFP_KERNEL);
What do we need the next_session index for?
> + if (ret < 0)
> + goto cleanup_em;
> +
> + kref_init(&session->ref);
> +
> + return session_id;
> +
> +cleanup_em:
> + kref_put(&em->refs, panthor_perf_destroy_em_kref);
> +
> +cleanup_eventfd:
> + eventfd_ctx_put(session->eventfd);
> +
> +cleanup_control_map:
> + drm_gem_vunmap_unlocked(control, &ctrl_map);
> +
> +cleanup_ring_map:
> + drm_gem_vunmap_unlocked(ringbuffer, &rb_map);
> +
> +cleanup_control:
> + drm_gem_object_put(control);
> +
> +cleanup_ringbuf:
> + drm_gem_object_put(ringbuffer);
> +
> +cleanup_session:
> + devm_kfree(ptdev->base.dev, session);
> +
> + return ret;
> +}
> +
> +static int session_stop(struct panthor_perf *perf, struct panthor_perf_session *session,
> + u64 user_data)
> +{
> + if (!test_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state))
> + return 0;
> +
> + const u32 extract_idx = session_read_extract_idx(session);
> + const u32 insert_idx = session_read_insert_idx(session);
> +
> + /* Must have at least one slot remaining in the ringbuffer to sample. */
> + if (WARN_ON_ONCE(!CIRC_SPACE_TO_END(insert_idx, extract_idx, session->ringbuf_slots)))
> + return -EBUSY;
> +
> + session->user_data = user_data;
> +
> + clear_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state);
> +
> + /* TODO Calls to the FW interface will go here in later patches. */
> + return 0;
> +}
> +
> +static int session_start(struct panthor_perf *perf, struct panthor_perf_session *session,
> + u64 user_data)
> +{
> + if (test_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state))
> + return 0;
> +
> + set_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state);
> +
> + /*
> + * For manual sampling sessions, a start command does not correspond to a sample,
> + * and so the user data gets discarded.
> + */
> + if (session->sample_freq_ns)
> + session->user_data = user_data;
> +
> + /* TODO Calls to the FW interface will go here in later patches. */
> + return 0;
> +}
> +
> +static int session_sample(struct panthor_perf *perf, struct panthor_perf_session *session,
> + u64 user_data)
> +{
> + if (!test_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state))
> + return -EACCES;
> +
> + const u32 extract_idx = session_read_extract_idx(session);
> + const u32 insert_idx = session_read_insert_idx(session);
> +
> + /* Manual sampling for periodic sessions is forbidden. */
> + if (session->sample_freq_ns)
> + return -EINVAL;
> +
> + /*
> + * Must have at least two slots remaining in the ringbuffer to sample: one for
> + * the current sample, and one for a stop sample, since a stop command should
> + * always be acknowledged by taking a final sample and stopping the session.
> + */
> + if (CIRC_SPACE_TO_END(insert_idx, extract_idx, session->ringbuf_slots) < 2)
> + return -EBUSY;
> +
> + session->sample_start_ns = ktime_get_raw_ns();
> + session->user_data = user_data;
> +
> + /* TODO Calls to the FW interface will go here in later patches. */
> + return 0;
> +}
> +
> +static int session_destroy(struct panthor_perf *perf, struct panthor_perf_session *session)
> +{
> + session_put(session);
> +
> + return 0;
> +}
> +
> +static int session_teardown(struct panthor_perf *perf, struct panthor_perf_session *session)
> +{
> + if (test_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state))
> + return -EINVAL;
> +
> + if (!list_empty(&session->waiting))
> + return -EBUSY;
> +
> + return session_destroy(perf, session);
> +}
> +
> +/**
> + * panthor_perf_session_teardown - Teardown the session associated with the @sid.
> + * @pfile: Open panthor file.
> + * @perf: Handle to the perf control structure.
> + * @sid: Session identifier.
> + *
> + * Destroys a stopped session where the last sample has been explicitly consumed
> + * or discarded. Active sessions will be ignored.
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +int panthor_perf_session_teardown(struct panthor_file *pfile, struct panthor_perf *perf, u32 sid)
> +{
> + int err;
> + struct panthor_perf_session *session;
> +
> + xa_lock(&perf->sessions);
> + session = __xa_store(&perf->sessions, sid, NULL, GFP_KERNEL);
Why not xa_erase() here instead?
> + if (xa_is_err(session)) {
> + err = xa_err(session);
> + goto restore;
> + }
> +
> + if (session->pfile != pfile) {
> + err = -EINVAL;
> + goto restore;
> + }
> +
> + session_get(session);
> + xa_unlock(&perf->sessions);
> +
> + err = session_teardown(perf, session);
> +
> + session_put(session);
I haven't made sure that reference counting is balanced, but noticed session_teardown() is already
putting the session's kref. I'll have a deeper look into it later on.
> +
> + return err;
> +
> +restore:
> + __xa_store(&perf->sessions, sid, session, GFP_KERNEL);
> + xa_unlock(&perf->sessions);
> +
> + return err;
> +}
> +
> +/**
> + * panthor_perf_session_start - Start sampling on a stopped session.
> + * @pfile: Open panthor file.
> + * @perf: Handle to the panthor perf control structure.
> + * @sid: Session identifier for the desired session.
> + * @user_data: An opaque value passed in from userspace.
> + *
> + * A session counts as stopped when it is created or when it is explicitly stopped after being
> + * started. Starting an active session is treated as a no-op.
> + *
> + * The @user_data parameter will be associated with all subsequent samples for a periodic
> + * sampling session and will be ignored for manual sampling ones in favor of the user data
> + * passed in the PERF_CONTROL.SAMPLE ioctl call.
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +int panthor_perf_session_start(struct panthor_file *pfile, struct panthor_perf *perf,
> + u32 sid, u64 user_data)
> +{
> + struct panthor_perf_session *session = session_find(pfile, perf, sid);
> + int err;
> +
> + if (IS_ERR_OR_NULL(session))
> + return IS_ERR(session) ? PTR_ERR(session) : -EINVAL;
> +
> + err = session_start(perf, session, user_data);
> +
> + session_put(session);
> +
> + return err;
> +}
> +
> +/**
> + * panthor_perf_session_stop - Stop sampling on an active session.
> + * @pfile: Open panthor file.
> + * @perf: Handle to the panthor perf control structure.
> + * @sid: Session identifier for the desired session.
> + * @user_data: An opaque value passed in from userspace.
> + *
> + * A session counts as active when it has been explicitly started via the PERF_CONTROL.START
> + * ioctl. Stopping a stopped session is treated as a no-op.
> + *
> + * To ensure data is not lost when sampling is stopping, there must always be at least one slot
> + * available for the final automatic sample, and the stop command will be rejected if there is not.
> + *
> + * The @user_data will always be associated with the final sample.
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +int panthor_perf_session_stop(struct panthor_file *pfile, struct panthor_perf *perf,
> + u32 sid, u64 user_data)
> +{
> + struct panthor_perf_session *session = session_find(pfile, perf, sid);
> + int err;
> +
> + if (IS_ERR_OR_NULL(session))
> + return IS_ERR(session) ? PTR_ERR(session) : -EINVAL;
> +
> + err = session_stop(perf, session, user_data);
> +
> + session_put(session);
> +
> + return err;
> +}
> +
> +/**
> + * panthor_perf_session_sample - Request a sample on a manual sampling session.
> + * @pfile: Open panthor file.
> + * @perf: Handle to the panthor perf control structure.
> + * @sid: Session identifier for the desired session.
> + * @user_data: An opaque value passed in from userspace.
> + *
> + * Only an active manual sampler is permitted to request samples directly. Failing to meet either
> + * of these conditions will cause the sampling request to be rejected. Requesting a manual sample
> + * with a full ringbuffer will see the request being rejected.
> + *
> + * The @user_data will always be unambiguously associated one-to-one with the resultant sample.
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +int panthor_perf_session_sample(struct panthor_file *pfile, struct panthor_perf *perf,
> + u32 sid, u64 user_data)
> +{
> + struct panthor_perf_session *session = session_find(pfile, perf, sid);
> + int err;
> +
> + if (IS_ERR_OR_NULL(session))
> + return IS_ERR(session) ? PTR_ERR(session) : -EINVAL;
> +
> + err = session_sample(perf, session, user_data);
> +
> + session_put(session);
> +
> + return err;
> +}
> +
> +/**
> + * panthor_perf_session_destroy - Destroy a sampling session associated with the @pfile.
> + * @perf: Handle to the panthor perf control structure.
> + * @pfile: The file being closed.
> + *
> + * Must be called when the corresponding userspace process is destroyed and cannot close its
> + * own sessions. As such, we offer no guarantees about data delivery.
> + */
> +void panthor_perf_session_destroy(struct panthor_file *pfile, struct panthor_perf *perf)
> +{
> + unsigned long sid;
> + struct panthor_perf_session *session;
> +
> + xa_for_each(&perf->sessions, sid, session)
> + {
> + if (session->pfile == pfile) {
> + session_destroy(perf, session);
> + xa_erase(&perf->sessions, sid);
> + }
> + }
> }
>
> /**
> @@ -146,10 +800,17 @@ void panthor_perf_unplug(struct panthor_device *ptdev)
> if (!perf)
> return;
>
> - if (!xa_empty(&perf->sessions))
> + if (!xa_empty(&perf->sessions)) {
> + unsigned long sid;
> + struct panthor_perf_session *session;
> +
> drm_err(&ptdev->base,
> "Performance counter sessions active when unplugging the driver!");
>
> + xa_for_each(&perf->sessions, sid, session)
> + session_destroy(perf, session);
> + }
> +
> xa_destroy(&perf->sessions);
>
> devm_kfree(ptdev->base.dev, ptdev->perf);
> diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h
> index 8a431431da6b..576d3ad46e6d 100644
> --- a/include/uapi/drm/panthor_drm.h
> +++ b/include/uapi/drm/panthor_drm.h
> @@ -458,6 +458,12 @@ enum drm_panthor_perf_block_type {
>
> /** @DRM_PANTHOR_PERF_BLOCK_SHADER: A shader core counter block. */
> DRM_PANTHOR_PERF_BLOCK_SHADER,
> +
> + /** @DRM_PANTHOR_PERF_BLOCK_LAST: Internal use only. */
> + DRM_PANTHOR_PERF_BLOCK_LAST = DRM_PANTHOR_PERF_BLOCK_SHADER,
> +
> + /** @DRM_PANTHOR_PERF_BLOCK_MAX: Internal use only. */
> + DRM_PANTHOR_PERF_BLOCK_MAX = DRM_PANTHOR_PERF_BLOCK_LAST + 1,
> };
>
> /**
> @@ -1368,6 +1374,44 @@ struct drm_panthor_perf_control {
> __u64 pointer;
> };
>
> +/**
> + * enum drm_panthor_perf_counter_set - The counter set to be requested from the hardware.
> + *
> + * The hardware supports a single performance counter set at a time, so requesting any set other
> + * than the primary may fail if another process is sampling at the same time.
> + *
> + * If in doubt, the primary counter set has the most commonly used counters and requires no
> + * additional permissions to open.
> + */
> +enum drm_panthor_perf_counter_set {
> + /**
> + * @DRM_PANTHOR_PERF_SET_PRIMARY: The default set configured on the hardware.
> + *
> + * This is the only set for which all counters in all blocks are defined.
> + */
> + DRM_PANTHOR_PERF_SET_PRIMARY,
> +
> + /**
> + * @DRM_PANTHOR_PERF_SET_SECONDARY: The secondary performance counter set.
> + *
> + * Some blocks may not have any defined counters for this set, and the block will
> + * have the UNAVAILABLE block state permanently set in the block header.
> + *
> + * Accessing this set requires the calling process to have the CAP_PERFMON capability.
> + */
> + DRM_PANTHOR_PERF_SET_SECONDARY,
> +
> + /**
> + * @DRM_PANTHOR_PERF_SET_TERTIARY: The tertiary performance counter set.
> + *
> + * Some blocks may not have any defined counters for this set, and the block will have
> + * the UNAVAILABLE block state permanently set in the block header. Note that the
> + * tertiary set has the fewest defined counter blocks.
> + *
> + * Accessing this set requires the calling process to have the CAP_PERFMON capability.
> + */
> + DRM_PANTHOR_PERF_SET_TERTIARY,
> +};
>
> /**
> * struct drm_panthor_perf_cmd_setup - Arguments passed to DRM_PANTHOR_IOCTL_PERF_CONTROL
> @@ -1375,13 +1419,17 @@ struct drm_panthor_perf_control {
> */
> struct drm_panthor_perf_cmd_setup {
> /**
> - * @block_set: Set of performance counter blocks.
> + * @block_set: Set of performance counter blocks, member of
> + * enum drm_panthor_perf_block_set.
> *
> * This is a global configuration and only one set can be active at a time. If
> * another client has already requested a counter set, any further requests
> * for a different counter set will fail and return an -EBUSY.
> *
> * If the requested set does not exist, the request will fail and return an -EINVAL.
> + *
> + * Some sets have additional requirements to be enabled, and the setup request will
> + * fail with an -EACCES if these requirements are not satisfied.
> */
Is this what we check inside session_validate_set() ?
> __u8 block_set;
>
> --
> 2.25.1
Adrian Larumbe
