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i915_perf.c
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i915_perf.c
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/*
* Copyright © 2015-2016 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* Authors:
* Robert Bragg <robert@sixbynine.org>
*/
/**
* DOC: i915 Perf Overview
*
* Gen graphics supports a large number of performance counters that can help
* driver and application developers understand and optimize their use of the
* GPU.
*
* This i915 perf interface enables userspace to configure and open a file
* descriptor representing a stream of GPU metrics which can then be read() as
* a stream of sample records.
*
* The interface is particularly suited to exposing buffered metrics that are
* captured by DMA from the GPU, unsynchronized with and unrelated to the CPU.
*
* Streams representing a single context are accessible to applications with a
* corresponding drm file descriptor, such that OpenGL can use the interface
* without special privileges. Access to system-wide metrics requires root
* privileges by default, unless changed via the dev.i915.perf_event_paranoid
* sysctl option.
*
*/
/**
* DOC: i915 Perf History and Comparison with Core Perf
*
* The interface was initially inspired by the core Perf infrastructure but
* some notable differences are:
*
* i915 perf file descriptors represent a "stream" instead of an "event"; where
* a perf event primarily corresponds to a single 64bit value, while a stream
* might sample sets of tightly-coupled counters, depending on the
* configuration. For example the Gen OA unit isn't designed to support
* orthogonal configurations of individual counters; it's configured for a set
* of related counters. Samples for an i915 perf stream capturing OA metrics
* will include a set of counter values packed in a compact HW specific format.
* The OA unit supports a number of different packing formats which can be
* selected by the user opening the stream. Perf has support for grouping
* events, but each event in the group is configured, validated and
* authenticated individually with separate system calls.
*
* i915 perf stream configurations are provided as an array of u64 (key,value)
* pairs, instead of a fixed struct with multiple miscellaneous config members,
* interleaved with event-type specific members.
*
* i915 perf doesn't support exposing metrics via an mmap'd circular buffer.
* The supported metrics are being written to memory by the GPU unsynchronized
* with the CPU, using HW specific packing formats for counter sets. Sometimes
* the constraints on HW configuration require reports to be filtered before it
* would be acceptable to expose them to unprivileged applications - to hide
* the metrics of other processes/contexts. For these use cases a read() based
* interface is a good fit, and provides an opportunity to filter data as it
* gets copied from the GPU mapped buffers to userspace buffers.
*
*
* Issues hit with first prototype based on Core Perf
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* The first prototype of this driver was based on the core perf
* infrastructure, and while we did make that mostly work, with some changes to
* perf, we found we were breaking or working around too many assumptions baked
* into perf's currently cpu centric design.
*
* In the end we didn't see a clear benefit to making perf's implementation and
* interface more complex by changing design assumptions while we knew we still
* wouldn't be able to use any existing perf based userspace tools.
*
* Also considering the Gen specific nature of the Observability hardware and
* how userspace will sometimes need to combine i915 perf OA metrics with
* side-band OA data captured via MI_REPORT_PERF_COUNT commands; we're
* expecting the interface to be used by a platform specific userspace such as
* OpenGL or tools. This is to say; we aren't inherently missing out on having
* a standard vendor/architecture agnostic interface by not using perf.
*
*
* For posterity, in case we might re-visit trying to adapt core perf to be
* better suited to exposing i915 metrics these were the main pain points we
* hit:
*
* - The perf based OA PMU driver broke some significant design assumptions:
*
* Existing perf pmus are used for profiling work on a cpu and we were
* introducing the idea of _IS_DEVICE pmus with different security
* implications, the need to fake cpu-related data (such as user/kernel
* registers) to fit with perf's current design, and adding _DEVICE records
* as a way to forward device-specific status records.
*
* The OA unit writes reports of counters into a circular buffer, without
* involvement from the CPU, making our PMU driver the first of a kind.
*
* Given the way we were periodically forward data from the GPU-mapped, OA
* buffer to perf's buffer, those bursts of sample writes looked to perf like
* we were sampling too fast and so we had to subvert its throttling checks.
*
* Perf supports groups of counters and allows those to be read via
* transactions internally but transactions currently seem designed to be
* explicitly initiated from the cpu (say in response to a userspace read())
* and while we could pull a report out of the OA buffer we can't
* trigger a report from the cpu on demand.
*
* Related to being report based; the OA counters are configured in HW as a
* set while perf generally expects counter configurations to be orthogonal.
* Although counters can be associated with a group leader as they are
* opened, there's no clear precedent for being able to provide group-wide
* configuration attributes (for example we want to let userspace choose the
* OA unit report format used to capture all counters in a set, or specify a
* GPU context to filter metrics on). We avoided using perf's grouping
* feature and forwarded OA reports to userspace via perf's 'raw' sample
* field. This suited our userspace well considering how coupled the counters
* are when dealing with normalizing. It would be inconvenient to split
* counters up into separate events, only to require userspace to recombine
* them. For Mesa it's also convenient to be forwarded raw, periodic reports
* for combining with the side-band raw reports it captures using
* MI_REPORT_PERF_COUNT commands.
*
* - As a side note on perf's grouping feature; there was also some concern
* that using PERF_FORMAT_GROUP as a way to pack together counter values
* would quite drastically inflate our sample sizes, which would likely
* lower the effective sampling resolutions we could use when the available
* memory bandwidth is limited.
*
* With the OA unit's report formats, counters are packed together as 32
* or 40bit values, with the largest report size being 256 bytes.
*
* PERF_FORMAT_GROUP values are 64bit, but there doesn't appear to be a
* documented ordering to the values, implying PERF_FORMAT_ID must also be
* used to add a 64bit ID before each value; giving 16 bytes per counter.
*
* Related to counter orthogonality; we can't time share the OA unit, while
* event scheduling is a central design idea within perf for allowing
* userspace to open + enable more events than can be configured in HW at any
* one time. The OA unit is not designed to allow re-configuration while in
* use. We can't reconfigure the OA unit without losing internal OA unit
* state which we can't access explicitly to save and restore. Reconfiguring
* the OA unit is also relatively slow, involving ~100 register writes. From
* userspace Mesa also depends on a stable OA configuration when emitting
* MI_REPORT_PERF_COUNT commands and importantly the OA unit can't be
* disabled while there are outstanding MI_RPC commands lest we hang the
* command streamer.
*
* The contents of sample records aren't extensible by device drivers (i.e.
* the sample_type bits). As an example; Sourab Gupta had been looking to
* attach GPU timestamps to our OA samples. We were shoehorning OA reports
* into sample records by using the 'raw' field, but it's tricky to pack more
* than one thing into this field because events/core.c currently only lets a
* pmu give a single raw data pointer plus len which will be copied into the
* ring buffer. To include more than the OA report we'd have to copy the
* report into an intermediate larger buffer. I'd been considering allowing a
* vector of data+len values to be specified for copying the raw data, but
* it felt like a kludge to being using the raw field for this purpose.
*
* - It felt like our perf based PMU was making some technical compromises
* just for the sake of using perf:
*
* perf_event_open() requires events to either relate to a pid or a specific
* cpu core, while our device pmu related to neither. Events opened with a
* pid will be automatically enabled/disabled according to the scheduling of
* that process - so not appropriate for us. When an event is related to a
* cpu id, perf ensures pmu methods will be invoked via an inter process
* interrupt on that core. To avoid invasive changes our userspace opened OA
* perf events for a specific cpu. This was workable but it meant the
* majority of the OA driver ran in atomic context, including all OA report
* forwarding, which wasn't really necessary in our case and seems to make
* our locking requirements somewhat complex as we handled the interaction
* with the rest of the i915 driver.
*/
#include <linux/anon_inodes.h>
#include <linux/nospec.h>
#include <linux/sizes.h>
#include <linux/uuid.h>
#include "gem/i915_gem_context.h"
#include "gem/i915_gem_internal.h"
#include "gt/intel_engine_pm.h"
#include "gt/intel_engine_regs.h"
#include "gt/intel_engine_user.h"
#include "gt/intel_execlists_submission.h"
#include "gt/intel_gpu_commands.h"
#include "gt/intel_gt.h"
#include "gt/intel_gt_clock_utils.h"
#include "gt/intel_gt_mcr.h"
#include "gt/intel_gt_print.h"
#include "gt/intel_gt_regs.h"
#include "gt/intel_lrc.h"
#include "gt/intel_lrc_reg.h"
#include "gt/intel_rc6.h"
#include "gt/intel_ring.h"
#include "gt/uc/intel_guc_slpc.h"
#include "i915_drv.h"
#include "i915_file_private.h"
#include "i915_perf.h"
#include "i915_perf_oa_regs.h"
#include "i915_reg.h"
/* HW requires this to be a power of two, between 128k and 16M, though driver
* is currently generally designed assuming the largest 16M size is used such
* that the overflow cases are unlikely in normal operation.
*/
#define OA_BUFFER_SIZE SZ_16M
#define OA_TAKEN(tail, head) ((tail - head) & (OA_BUFFER_SIZE - 1))
/**
* DOC: OA Tail Pointer Race
*
* There's a HW race condition between OA unit tail pointer register updates and
* writes to memory whereby the tail pointer can sometimes get ahead of what's
* been written out to the OA buffer so far (in terms of what's visible to the
* CPU).
*
* Although this can be observed explicitly while copying reports to userspace
* by checking for a zeroed report-id field in tail reports, we want to account
* for this earlier, as part of the oa_buffer_check_unlocked to avoid lots of
* redundant read() attempts.
*
* We workaround this issue in oa_buffer_check_unlocked() by reading the reports
* in the OA buffer, starting from the tail reported by the HW until we find a
* report with its first 2 dwords not 0 meaning its previous report is
* completely in memory and ready to be read. Those dwords are also set to 0
* once read and the whole buffer is cleared upon OA buffer initialization. The
* first dword is the reason for this report while the second is the timestamp,
* making the chances of having those 2 fields at 0 fairly unlikely. A more
* detailed explanation is available in oa_buffer_check_unlocked().
*
* Most of the implementation details for this workaround are in
* oa_buffer_check_unlocked() and _append_oa_reports()
*
* Note for posterity: previously the driver used to define an effective tail
* pointer that lagged the real pointer by a 'tail margin' measured in bytes
* derived from %OA_TAIL_MARGIN_NSEC and the configured sampling frequency.
* This was flawed considering that the OA unit may also automatically generate
* non-periodic reports (such as on context switch) or the OA unit may be
* enabled without any periodic sampling.
*/
#define OA_TAIL_MARGIN_NSEC 100000ULL
#define INVALID_TAIL_PTR 0xffffffff
/* The default frequency for checking whether the OA unit has written new
* reports to the circular OA buffer...
*/
#define DEFAULT_POLL_FREQUENCY_HZ 200
#define DEFAULT_POLL_PERIOD_NS (NSEC_PER_SEC / DEFAULT_POLL_FREQUENCY_HZ)
/* for sysctl proc_dointvec_minmax of dev.i915.perf_stream_paranoid */
static u32 i915_perf_stream_paranoid = true;
/* The maximum exponent the hardware accepts is 63 (essentially it selects one
* of the 64bit timestamp bits to trigger reports from) but there's currently
* no known use case for sampling as infrequently as once per 47 thousand years.
*
* Since the timestamps included in OA reports are only 32bits it seems
* reasonable to limit the OA exponent where it's still possible to account for
* overflow in OA report timestamps.
*/
#define OA_EXPONENT_MAX 31
#define INVALID_CTX_ID 0xffffffff
/* On Gen8+ automatically triggered OA reports include a 'reason' field... */
#define OAREPORT_REASON_MASK 0x3f
#define OAREPORT_REASON_MASK_EXTENDED 0x7f
#define OAREPORT_REASON_SHIFT 19
#define OAREPORT_REASON_TIMER (1<<0)
#define OAREPORT_REASON_CTX_SWITCH (1<<3)
#define OAREPORT_REASON_CLK_RATIO (1<<5)
#define HAS_MI_SET_PREDICATE(i915) (GRAPHICS_VER_FULL(i915) >= IP_VER(12, 50))
/* For sysctl proc_dointvec_minmax of i915_oa_max_sample_rate
*
* The highest sampling frequency we can theoretically program the OA unit
* with is always half the timestamp frequency: E.g. 6.25Mhz for Haswell.
*
* Initialized just before we register the sysctl parameter.
*/
static int oa_sample_rate_hard_limit;
/* Theoretically we can program the OA unit to sample every 160ns but don't
* allow that by default unless root...
*
* The default threshold of 100000Hz is based on perf's similar
* kernel.perf_event_max_sample_rate sysctl parameter.
*/
static u32 i915_oa_max_sample_rate = 100000;
/* XXX: beware if future OA HW adds new report formats that the current
* code assumes all reports have a power-of-two size and ~(size - 1) can
* be used as a mask to align the OA tail pointer.
*/
static const struct i915_oa_format oa_formats[I915_OA_FORMAT_MAX] = {
[I915_OA_FORMAT_A13] = { 0, 64 },
[I915_OA_FORMAT_A29] = { 1, 128 },
[I915_OA_FORMAT_A13_B8_C8] = { 2, 128 },
/* A29_B8_C8 Disallowed as 192 bytes doesn't factor into buffer size */
[I915_OA_FORMAT_B4_C8] = { 4, 64 },
[I915_OA_FORMAT_A45_B8_C8] = { 5, 256 },
[I915_OA_FORMAT_B4_C8_A16] = { 6, 128 },
[I915_OA_FORMAT_C4_B8] = { 7, 64 },
[I915_OA_FORMAT_A12] = { 0, 64 },
[I915_OA_FORMAT_A12_B8_C8] = { 2, 128 },
[I915_OA_FORMAT_A32u40_A4u32_B8_C8] = { 5, 256 },
[I915_OAR_FORMAT_A32u40_A4u32_B8_C8] = { 5, 256 },
[I915_OA_FORMAT_A24u40_A14u32_B8_C8] = { 5, 256 },
[I915_OAM_FORMAT_MPEC8u64_B8_C8] = { 1, 192, TYPE_OAM, HDR_64_BIT },
[I915_OAM_FORMAT_MPEC8u32_B8_C8] = { 2, 128, TYPE_OAM, HDR_64_BIT },
};
static const u32 mtl_oa_base[] = {
[PERF_GROUP_OAM_SAMEDIA_0] = 0x393000,
};
#define SAMPLE_OA_REPORT (1<<0)
/**
* struct perf_open_properties - for validated properties given to open a stream
* @sample_flags: `DRM_I915_PERF_PROP_SAMPLE_*` properties are tracked as flags
* @single_context: Whether a single or all gpu contexts should be monitored
* @hold_preemption: Whether the preemption is disabled for the filtered
* context
* @ctx_handle: A gem ctx handle for use with @single_context
* @metrics_set: An ID for an OA unit metric set advertised via sysfs
* @oa_format: An OA unit HW report format
* @oa_periodic: Whether to enable periodic OA unit sampling
* @oa_period_exponent: The OA unit sampling period is derived from this
* @engine: The engine (typically rcs0) being monitored by the OA unit
* @has_sseu: Whether @sseu was specified by userspace
* @sseu: internal SSEU configuration computed either from the userspace
* specified configuration in the opening parameters or a default value
* (see get_default_sseu_config())
* @poll_oa_period: The period in nanoseconds at which the CPU will check for OA
* data availability
*
* As read_properties_unlocked() enumerates and validates the properties given
* to open a stream of metrics the configuration is built up in the structure
* which starts out zero initialized.
*/
struct perf_open_properties {
u32 sample_flags;
u64 single_context:1;
u64 hold_preemption:1;
u64 ctx_handle;
/* OA sampling state */
int metrics_set;
int oa_format;
bool oa_periodic;
int oa_period_exponent;
struct intel_engine_cs *engine;
bool has_sseu;
struct intel_sseu sseu;
u64 poll_oa_period;
};
struct i915_oa_config_bo {
struct llist_node node;
struct i915_oa_config *oa_config;
struct i915_vma *vma;
};
static struct ctl_table_header *sysctl_header;
static enum hrtimer_restart oa_poll_check_timer_cb(struct hrtimer *hrtimer);
void i915_oa_config_release(struct kref *ref)
{
struct i915_oa_config *oa_config =
container_of(ref, typeof(*oa_config), ref);
kfree(oa_config->flex_regs);
kfree(oa_config->b_counter_regs);
kfree(oa_config->mux_regs);
kfree_rcu(oa_config, rcu);
}
struct i915_oa_config *
i915_perf_get_oa_config(struct i915_perf *perf, int metrics_set)
{
struct i915_oa_config *oa_config;
rcu_read_lock();
oa_config = idr_find(&perf->metrics_idr, metrics_set);
if (oa_config)
oa_config = i915_oa_config_get(oa_config);
rcu_read_unlock();
return oa_config;
}
static void free_oa_config_bo(struct i915_oa_config_bo *oa_bo)
{
i915_oa_config_put(oa_bo->oa_config);
i915_vma_put(oa_bo->vma);
kfree(oa_bo);
}
static inline const
struct i915_perf_regs *__oa_regs(struct i915_perf_stream *stream)
{
return &stream->engine->oa_group->regs;
}
static u32 gen12_oa_hw_tail_read(struct i915_perf_stream *stream)
{
struct intel_uncore *uncore = stream->uncore;
return intel_uncore_read(uncore, __oa_regs(stream)->oa_tail_ptr) &
GEN12_OAG_OATAILPTR_MASK;
}
static u32 gen8_oa_hw_tail_read(struct i915_perf_stream *stream)
{
struct intel_uncore *uncore = stream->uncore;
return intel_uncore_read(uncore, GEN8_OATAILPTR) & GEN8_OATAILPTR_MASK;
}
static u32 gen7_oa_hw_tail_read(struct i915_perf_stream *stream)
{
struct intel_uncore *uncore = stream->uncore;
u32 oastatus1 = intel_uncore_read(uncore, GEN7_OASTATUS1);
return oastatus1 & GEN7_OASTATUS1_TAIL_MASK;
}
#define oa_report_header_64bit(__s) \
((__s)->oa_buffer.format->header == HDR_64_BIT)
static u64 oa_report_id(struct i915_perf_stream *stream, void *report)
{
return oa_report_header_64bit(stream) ? *(u64 *)report : *(u32 *)report;
}
static u64 oa_report_reason(struct i915_perf_stream *stream, void *report)
{
return (oa_report_id(stream, report) >> OAREPORT_REASON_SHIFT) &
(GRAPHICS_VER(stream->perf->i915) == 12 ?
OAREPORT_REASON_MASK_EXTENDED :
OAREPORT_REASON_MASK);
}
static void oa_report_id_clear(struct i915_perf_stream *stream, u32 *report)
{
if (oa_report_header_64bit(stream))
*(u64 *)report = 0;
else
*report = 0;
}
static bool oa_report_ctx_invalid(struct i915_perf_stream *stream, void *report)
{
return !(oa_report_id(stream, report) &
stream->perf->gen8_valid_ctx_bit);
}
static u64 oa_timestamp(struct i915_perf_stream *stream, void *report)
{
return oa_report_header_64bit(stream) ?
*((u64 *)report + 1) :
*((u32 *)report + 1);
}
static void oa_timestamp_clear(struct i915_perf_stream *stream, u32 *report)
{
if (oa_report_header_64bit(stream))
*(u64 *)&report[2] = 0;
else
report[1] = 0;
}
static u32 oa_context_id(struct i915_perf_stream *stream, u32 *report)
{
u32 ctx_id = oa_report_header_64bit(stream) ? report[4] : report[2];
return ctx_id & stream->specific_ctx_id_mask;
}
static void oa_context_id_squash(struct i915_perf_stream *stream, u32 *report)
{
if (oa_report_header_64bit(stream))
report[4] = INVALID_CTX_ID;
else
report[2] = INVALID_CTX_ID;
}
/**
* oa_buffer_check_unlocked - check for data and update tail ptr state
* @stream: i915 stream instance
*
* This is either called via fops (for blocking reads in user ctx) or the poll
* check hrtimer (atomic ctx) to check the OA buffer tail pointer and check
* if there is data available for userspace to read.
*
* This function is central to providing a workaround for the OA unit tail
* pointer having a race with respect to what data is visible to the CPU.
* It is responsible for reading tail pointers from the hardware and giving
* the pointers time to 'age' before they are made available for reading.
* (See description of OA_TAIL_MARGIN_NSEC above for further details.)
*
* Besides returning true when there is data available to read() this function
* also updates the tail in the oa_buffer object.
*
* Note: It's safe to read OA config state here unlocked, assuming that this is
* only called while the stream is enabled, while the global OA configuration
* can't be modified.
*
* Returns: %true if the OA buffer contains data, else %false
*/
static bool oa_buffer_check_unlocked(struct i915_perf_stream *stream)
{
u32 gtt_offset = i915_ggtt_offset(stream->oa_buffer.vma);
int report_size = stream->oa_buffer.format->size;
u32 tail, hw_tail;
unsigned long flags;
bool pollin;
u32 partial_report_size;
/* We have to consider the (unlikely) possibility that read() errors
* could result in an OA buffer reset which might reset the head and
* tail state.
*/
spin_lock_irqsave(&stream->oa_buffer.ptr_lock, flags);
hw_tail = stream->perf->ops.oa_hw_tail_read(stream);
hw_tail -= gtt_offset;
/* The tail pointer increases in 64 byte increments, not in report_size
* steps. Also the report size may not be a power of 2. Compute
* potentially partially landed report in the OA buffer
*/
partial_report_size = OA_TAKEN(hw_tail, stream->oa_buffer.tail);
partial_report_size %= report_size;
/* Subtract partial amount off the tail */
hw_tail = OA_TAKEN(hw_tail, partial_report_size);
tail = hw_tail;
/* Walk the stream backward until we find a report with report
* id and timestmap not at 0. Since the circular buffer pointers
* progress by increments of 64 bytes and that reports can be up
* to 256 bytes long, we can't tell whether a report has fully
* landed in memory before the report id and timestamp of the
* following report have effectively landed.
*
* This is assuming that the writes of the OA unit land in
* memory in the order they were written to.
* If not : (╯°□°)╯︵ ┻━┻
*/
while (OA_TAKEN(tail, stream->oa_buffer.tail) >= report_size) {
void *report = stream->oa_buffer.vaddr + tail;
if (oa_report_id(stream, report) ||
oa_timestamp(stream, report))
break;
tail = (tail - report_size) & (OA_BUFFER_SIZE - 1);
}
if (OA_TAKEN(hw_tail, tail) > report_size &&
__ratelimit(&stream->perf->tail_pointer_race))
drm_notice(&stream->uncore->i915->drm,
"unlanded report(s) head=0x%x tail=0x%x hw_tail=0x%x\n",
stream->oa_buffer.head, tail, hw_tail);
stream->oa_buffer.tail = tail;
pollin = OA_TAKEN(stream->oa_buffer.tail,
stream->oa_buffer.head) >= report_size;
spin_unlock_irqrestore(&stream->oa_buffer.ptr_lock, flags);
return pollin;
}
/**
* append_oa_status - Appends a status record to a userspace read() buffer.
* @stream: An i915-perf stream opened for OA metrics
* @buf: destination buffer given by userspace
* @count: the number of bytes userspace wants to read
* @offset: (inout): the current position for writing into @buf
* @type: The kind of status to report to userspace
*
* Writes a status record (such as `DRM_I915_PERF_RECORD_OA_REPORT_LOST`)
* into the userspace read() buffer.
*
* The @buf @offset will only be updated on success.
*
* Returns: 0 on success, negative error code on failure.
*/
static int append_oa_status(struct i915_perf_stream *stream,
char __user *buf,
size_t count,
size_t *offset,
enum drm_i915_perf_record_type type)
{
struct drm_i915_perf_record_header header = { type, 0, sizeof(header) };
if ((count - *offset) < header.size)
return -ENOSPC;
if (copy_to_user(buf + *offset, &header, sizeof(header)))
return -EFAULT;
(*offset) += header.size;
return 0;
}
/**
* append_oa_sample - Copies single OA report into userspace read() buffer.
* @stream: An i915-perf stream opened for OA metrics
* @buf: destination buffer given by userspace
* @count: the number of bytes userspace wants to read
* @offset: (inout): the current position for writing into @buf
* @report: A single OA report to (optionally) include as part of the sample
*
* The contents of a sample are configured through `DRM_I915_PERF_PROP_SAMPLE_*`
* properties when opening a stream, tracked as `stream->sample_flags`. This
* function copies the requested components of a single sample to the given
* read() @buf.
*
* The @buf @offset will only be updated on success.
*
* Returns: 0 on success, negative error code on failure.
*/
static int append_oa_sample(struct i915_perf_stream *stream,
char __user *buf,
size_t count,
size_t *offset,
const u8 *report)
{
int report_size = stream->oa_buffer.format->size;
struct drm_i915_perf_record_header header;
int report_size_partial;
u8 *oa_buf_end;
header.type = DRM_I915_PERF_RECORD_SAMPLE;
header.pad = 0;
header.size = stream->sample_size;
if ((count - *offset) < header.size)
return -ENOSPC;
buf += *offset;
if (copy_to_user(buf, &header, sizeof(header)))
return -EFAULT;
buf += sizeof(header);
oa_buf_end = stream->oa_buffer.vaddr + OA_BUFFER_SIZE;
report_size_partial = oa_buf_end - report;
if (report_size_partial < report_size) {
if (copy_to_user(buf, report, report_size_partial))
return -EFAULT;
buf += report_size_partial;
if (copy_to_user(buf, stream->oa_buffer.vaddr,
report_size - report_size_partial))
return -EFAULT;
} else if (copy_to_user(buf, report, report_size)) {
return -EFAULT;
}
(*offset) += header.size;
return 0;
}
/**
* gen8_append_oa_reports - Copies all buffered OA reports into
* userspace read() buffer.
* @stream: An i915-perf stream opened for OA metrics
* @buf: destination buffer given by userspace
* @count: the number of bytes userspace wants to read
* @offset: (inout): the current position for writing into @buf
*
* Notably any error condition resulting in a short read (-%ENOSPC or
* -%EFAULT) will be returned even though one or more records may
* have been successfully copied. In this case it's up to the caller
* to decide if the error should be squashed before returning to
* userspace.
*
* Note: reports are consumed from the head, and appended to the
* tail, so the tail chases the head?... If you think that's mad
* and back-to-front you're not alone, but this follows the
* Gen PRM naming convention.
*
* Returns: 0 on success, negative error code on failure.
*/
static int gen8_append_oa_reports(struct i915_perf_stream *stream,
char __user *buf,
size_t count,
size_t *offset)
{
struct intel_uncore *uncore = stream->uncore;
int report_size = stream->oa_buffer.format->size;
u8 *oa_buf_base = stream->oa_buffer.vaddr;
u32 gtt_offset = i915_ggtt_offset(stream->oa_buffer.vma);
u32 mask = (OA_BUFFER_SIZE - 1);
size_t start_offset = *offset;
unsigned long flags;
u32 head, tail;
int ret = 0;
if (drm_WARN_ON(&uncore->i915->drm, !stream->enabled))
return -EIO;
spin_lock_irqsave(&stream->oa_buffer.ptr_lock, flags);
head = stream->oa_buffer.head;
tail = stream->oa_buffer.tail;
spin_unlock_irqrestore(&stream->oa_buffer.ptr_lock, flags);
/*
* An out of bounds or misaligned head or tail pointer implies a driver
* bug since we validate + align the tail pointers we read from the
* hardware and we are in full control of the head pointer which should
* only be incremented by multiples of the report size.
*/
if (drm_WARN_ONCE(&uncore->i915->drm,
head > OA_BUFFER_SIZE ||
tail > OA_BUFFER_SIZE,
"Inconsistent OA buffer pointers: head = %u, tail = %u\n",
head, tail))
return -EIO;
for (/* none */;
OA_TAKEN(tail, head);
head = (head + report_size) & mask) {
u8 *report = oa_buf_base + head;
u32 *report32 = (void *)report;
u32 ctx_id;
u64 reason;
/*
* The reason field includes flags identifying what
* triggered this specific report (mostly timer
* triggered or e.g. due to a context switch).
*/
reason = oa_report_reason(stream, report);
ctx_id = oa_context_id(stream, report32);
/*
* Squash whatever is in the CTX_ID field if it's marked as
* invalid to be sure we avoid false-positive, single-context
* filtering below...
*
* Note: that we don't clear the valid_ctx_bit so userspace can
* understand that the ID has been squashed by the kernel.
*
* Update:
*
* On XEHP platforms the behavior of context id valid bit has
* changed compared to prior platforms. To describe this, we
* define a few terms:
*
* context-switch-report: This is a report with the reason type
* being context-switch. It is generated when a context switches
* out.
*
* context-valid-bit: A bit that is set in the report ID field
* to indicate that a valid context has been loaded.
*
* gpu-idle: A condition characterized by a
* context-switch-report with context-valid-bit set to 0.
*
* On prior platforms, context-id-valid bit is set to 0 only
* when GPU goes idle. In all other reports, it is set to 1.
*
* On XEHP platforms, context-valid-bit is set to 1 in a context
* switch report if a new context switched in. For all other
* reports it is set to 0.
*
* This change in behavior causes an issue with MMIO triggered
* reports. MMIO triggered reports have the markers in the
* context ID field and the context-valid-bit is 0. The logic
* below to squash the context ID would render the report
* useless since the user will not be able to find it in the OA
* buffer. Since MMIO triggered reports exist only on XEHP,
* we should avoid squashing these for XEHP platforms.
*/
if (oa_report_ctx_invalid(stream, report) &&
GRAPHICS_VER_FULL(stream->engine->i915) < IP_VER(12, 50)) {
ctx_id = INVALID_CTX_ID;
oa_context_id_squash(stream, report32);
}
/*
* NB: For Gen 8 the OA unit no longer supports clock gating
* off for a specific context and the kernel can't securely
* stop the counters from updating as system-wide / global
* values.
*
* Automatic reports now include a context ID so reports can be
* filtered on the cpu but it's not worth trying to
* automatically subtract/hide counter progress for other
* contexts while filtering since we can't stop userspace
* issuing MI_REPORT_PERF_COUNT commands which would still
* provide a side-band view of the real values.
*
* To allow userspace (such as Mesa/GL_INTEL_performance_query)
* to normalize counters for a single filtered context then it
* needs be forwarded bookend context-switch reports so that it
* can track switches in between MI_REPORT_PERF_COUNT commands
* and can itself subtract/ignore the progress of counters
* associated with other contexts. Note that the hardware
* automatically triggers reports when switching to a new
* context which are tagged with the ID of the newly active
* context. To avoid the complexity (and likely fragility) of
* reading ahead while parsing reports to try and minimize
* forwarding redundant context switch reports (i.e. between
* other, unrelated contexts) we simply elect to forward them
* all.
*
* We don't rely solely on the reason field to identify context
* switches since it's not-uncommon for periodic samples to
* identify a switch before any 'context switch' report.
*/
if (!stream->ctx ||
stream->specific_ctx_id == ctx_id ||
stream->oa_buffer.last_ctx_id == stream->specific_ctx_id ||
reason & OAREPORT_REASON_CTX_SWITCH) {
/*
* While filtering for a single context we avoid
* leaking the IDs of other contexts.
*/
if (stream->ctx &&
stream->specific_ctx_id != ctx_id) {
oa_context_id_squash(stream, report32);
}
ret = append_oa_sample(stream, buf, count, offset,
report);
if (ret)
break;
stream->oa_buffer.last_ctx_id = ctx_id;
}
if (is_power_of_2(report_size)) {
/*
* Clear out the report id and timestamp as a means
* to detect unlanded reports.
*/
oa_report_id_clear(stream, report32);
oa_timestamp_clear(stream, report32);
} else {
u8 *oa_buf_end = stream->oa_buffer.vaddr +
OA_BUFFER_SIZE;
u32 part = oa_buf_end - (u8 *)report32;
/* Zero out the entire report */
if (report_size <= part) {
memset(report32, 0, report_size);
} else {
memset(report32, 0, part);
memset(oa_buf_base, 0, report_size - part);
}
}
}
if (start_offset != *offset) {
i915_reg_t oaheadptr;
oaheadptr = GRAPHICS_VER(stream->perf->i915) == 12 ?
__oa_regs(stream)->oa_head_ptr :
GEN8_OAHEADPTR;
spin_lock_irqsave(&stream->oa_buffer.ptr_lock, flags);
/*
* We removed the gtt_offset for the copy loop above, indexing
* relative to oa_buf_base so put back here...
*/
intel_uncore_write(uncore, oaheadptr,
(head + gtt_offset) & GEN12_OAG_OAHEADPTR_MASK);
stream->oa_buffer.head = head;
spin_unlock_irqrestore(&stream->oa_buffer.ptr_lock, flags);
}
return ret;
}
/**
* gen8_oa_read - copy status records then buffered OA reports
* @stream: An i915-perf stream opened for OA metrics
* @buf: destination buffer given by userspace
* @count: the number of bytes userspace wants to read
* @offset: (inout): the current position for writing into @buf
*
* Checks OA unit status registers and if necessary appends corresponding
* status records for userspace (such as for a buffer full condition) and then
* initiate appending any buffered OA reports.
*
* Updates @offset according to the number of bytes successfully copied into
* the userspace buffer.
*
* NB: some data may be successfully copied to the userspace buffer
* even if an error is returned, and this is reflected in the
* updated @offset.
*
* Returns: zero on success or a negative error code
*/
static int gen8_oa_read(struct i915_perf_stream *stream,
char __user *buf,
size_t count,
size_t *offset)
{
struct intel_uncore *uncore = stream->uncore;
u32 oastatus;
i915_reg_t oastatus_reg;
int ret;
if (drm_WARN_ON(&uncore->i915->drm, !stream->oa_buffer.vaddr))
return -EIO;
oastatus_reg = GRAPHICS_VER(stream->perf->i915) == 12 ?
__oa_regs(stream)->oa_status :
GEN8_OASTATUS;
oastatus = intel_uncore_read(uncore, oastatus_reg);
/*
* We treat OABUFFER_OVERFLOW as a significant error:
*
* Although theoretically we could handle this more gracefully
* sometimes, some Gens don't correctly suppress certain
* automatically triggered reports in this condition and so we
* have to assume that old reports are now being trampled
* over.
*
* Considering how we don't currently give userspace control
* over the OA buffer size and always configure a large 16MB
* buffer, then a buffer overflow does anyway likely indicate
* that something has gone quite badly wrong.
*/
if (oastatus & GEN8_OASTATUS_OABUFFER_OVERFLOW) {
ret = append_oa_status(stream, buf, count, offset,
DRM_I915_PERF_RECORD_OA_BUFFER_LOST);
if (ret)
return ret;
drm_dbg(&stream->perf->i915->drm,
"OA buffer overflow (exponent = %d): force restart\n",
stream->period_exponent);
stream->perf->ops.oa_disable(stream);
stream->perf->ops.oa_enable(stream);
/*
* Note: .oa_enable() is expected to re-init the oabuffer and
* reset GEN8_OASTATUS for us
*/
oastatus = intel_uncore_read(uncore, oastatus_reg);
}
if (oastatus & GEN8_OASTATUS_REPORT_LOST) {
ret = append_oa_status(stream, buf, count, offset,
DRM_I915_PERF_RECORD_OA_REPORT_LOST);
if (ret)
return ret;