[Intel-gfx] [PATCH 4/4] drm/i915/perf: Map OA buffer to user space for gen12 performance query
Lionel Landwerlin
lionel.g.landwerlin at intel.com
Thu Jul 23 09:31:30 UTC 2020
On 22/07/2020 08:55, Umesh Nerlige Ramappa wrote:
> From: Piotr Maciejewski <piotr.maciejewski at intel.com>
>
> i915 used to support time based sampling mode which is good for overall
> system monitoring, but is not enough for query mode used to measure a
> single draw call or dispatch. Gen9-Gen11 are using current i915 perf
> implementation for query, but Gen12+ requires a new approach for query
> based on triggered reports within oa buffer.
>
> Triggering reports into the OA buffer is achieved by writing into a
> a trigger register. Optionally an unused counter/register is set with a
> marker value such that a triggered report can be identified in the OA
> buffer. Reports are usually triggered at the start and end of work that
> is measured.
>
> Since OA buffer is large and queries can be frequent, an efficient way
> to look for triggered reports is required. By knowing the current head
> and tail offsets into the OA buffer, it is easier to determine the
> locality of the reports of interest.
>
> Current perf OA interface does not expose head/tail information to the
> user and it filters out invalid reports before sending data to user.
> Also considering limited size of user buffer used during a query,
> creating a 1:1 copy of the OA buffer at the user space added undesired
> complexity.
>
> The solution was to map the OA buffer to user space provided
>
> (1) that it is accessed from a privileged user.
> (2) OA report filtering is not used.
>
> These 2 conditions would satisfy the safety criteria that the current
> perf interface addresses.
>
> To enable the query:
> - Add an ioctl to expose head and tail to the user
> - Add an ioctl to return size and offset of the OA buffer
> - Map the OA buffer to the user space
>
> v2:
> - Improve commit message (Chris)
> - Do not mmap based on gem object filp. Instead, use perf_fd and support
> mmap syscall (Chris)
> - Pass non-zero offset in mmap to enforce the right object is
> mapped (Chris)
> - Do not expose gpu_address (Chris)
> - Verify start and length of vma for page alignment (Lionel)
> - Move SQNTL config out (Lionel)
>
> v3: (Chris)
> - Omit redundant checks
> - Return VM_FAULT_SIGBUS is old stream is closed
> - Maintain reference counts to stream in vm_open and vm_close
> - Use switch to identify object to be mapped
>
> v4: Call kref_put on closing perf fd (Chris)
>
> Signed-off-by: Piotr Maciejewski <piotr.maciejewski at intel.com>
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
> ---
> drivers/gpu/drm/i915/gem/i915_gem_mman.c | 2 +-
> drivers/gpu/drm/i915/gem/i915_gem_mman.h | 2 +
> drivers/gpu/drm/i915/i915_perf.c | 211 ++++++++++++++++++++++-
> drivers/gpu/drm/i915/i915_perf_types.h | 17 ++
> include/uapi/drm/i915_drm.h | 32 ++++
> 5 files changed, 261 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> index b23368529a40..7c4b9b0c334b 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> @@ -204,7 +204,7 @@ compute_partial_view(const struct drm_i915_gem_object *obj,
> return view;
> }
>
> -static vm_fault_t i915_error_to_vmf_fault(int err)
> +vm_fault_t i915_error_to_vmf_fault(int err)
> {
> switch (err) {
> default:
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.h b/drivers/gpu/drm/i915/gem/i915_gem_mman.h
> index efee9e0d2508..1190a3a228ea 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.h
> @@ -29,4 +29,6 @@ void i915_gem_object_release_mmap_gtt(struct drm_i915_gem_object *obj);
>
> void i915_gem_object_release_mmap_offset(struct drm_i915_gem_object *obj);
>
> +vm_fault_t i915_error_to_vmf_fault(int err);
> +
> #endif
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 2f23aad12c60..331c3f9c59e2 100644
> --- a/drivers/gpu/drm/i915/i915_perf.c
> +++ b/drivers/gpu/drm/i915/i915_perf.c
> @@ -192,10 +192,12 @@
> */
>
> #include <linux/anon_inodes.h>
> +#include <linux/mman.h>
> #include <linux/sizes.h>
> #include <linux/uuid.h>
>
> #include "gem/i915_gem_context.h"
> +#include "gem/i915_gem_mman.h"
> #include "gt/intel_engine_pm.h"
> #include "gt/intel_engine_user.h"
> #include "gt/intel_gt.h"
> @@ -378,6 +380,24 @@ static struct ctl_table_header *sysctl_header;
>
> static enum hrtimer_restart oa_poll_check_timer_cb(struct hrtimer *hrtimer);
>
> +static void free_stream(struct kref *kref)
> +{
> + struct i915_perf_stream *stream =
> + container_of(kref, typeof(*stream), refcount);
> +
> + kfree(stream);
> +}
> +
> +static void perf_stream_get(struct i915_perf_stream *stream)
> +{
> + kref_get(&stream->refcount);
> +}
> +
> +static void perf_stream_put(struct i915_perf_stream *stream)
> +{
> + kref_put(&stream->refcount, free_stream);
> +}
> +
> void i915_oa_config_release(struct kref *ref)
> {
> struct i915_oa_config *oa_config =
> @@ -434,6 +454,30 @@ static u32 gen7_oa_hw_tail_read(struct i915_perf_stream *stream)
> return oastatus1 & GEN7_OASTATUS1_TAIL_MASK;
> }
>
> +static u32 gen12_oa_hw_head_read(struct i915_perf_stream *stream)
> +{
> + struct intel_uncore *uncore = stream->uncore;
> +
> + return intel_uncore_read(uncore, GEN12_OAG_OAHEADPTR) &
> + GEN12_OAG_OAHEADPTR_MASK;
> +}
> +
> +static u32 gen8_oa_hw_head_read(struct i915_perf_stream *stream)
> +{
> + struct intel_uncore *uncore = stream->uncore;
> +
> + return intel_uncore_read(uncore, GEN8_OAHEADPTR) &
> + GEN8_OAHEADPTR_MASK;
> +}
> +
> +static u32 gen7_oa_hw_head_read(struct i915_perf_stream *stream)
> +{
> + struct intel_uncore *uncore = stream->uncore;
> + u32 oastatus2 = intel_uncore_read(uncore, GEN7_OASTATUS2);
> +
> + return oastatus2 & GEN7_OASTATUS2_HEAD_MASK;
> +}
> +
> /**
> * oa_buffer_check_unlocked - check for data and update tail ptr state
> * @stream: i915 stream instance
> @@ -2934,6 +2978,7 @@ static int i915_oa_stream_init(struct i915_perf_stream *stream,
> stream->poll_check_timer.function = oa_poll_check_timer_cb;
> init_waitqueue_head(&stream->poll_wq);
> spin_lock_init(&stream->oa_buffer.ptr_lock);
> + kref_init(&stream->refcount);
>
> return 0;
>
> @@ -3214,6 +3259,69 @@ static long i915_perf_config_locked(struct i915_perf_stream *stream,
> return ret;
> }
>
> +/**
> + * i915_perf_oa_buffer_head_tail_locked - head and tail of the OA buffer
> + * @stream: i915 perf stream
> + * @arg: pointer to oa buffer head and tail filled by this function.
> + */
> +static int i915_perf_oa_buffer_head_tail_locked(struct i915_perf_stream *stream,
> + unsigned long arg)
> +{
> + struct drm_i915_perf_oa_buffer_head_tail ht;
> + void __user *output = (void __user *)arg;
> + u32 gtt_offset = i915_ggtt_offset(stream->oa_buffer.vma);
> +
> + if (i915_perf_stream_paranoid && !perfmon_capable()) {
> + DRM_DEBUG("Insufficient privileges to access OA buffer info\n");
> + return -EACCES;
> + }
> +
> + if (!output)
> + return -EINVAL;
> +
> + memset(&ht, 0, sizeof(ht));
> +
> + ht.head = stream->perf->ops.oa_hw_head_read(stream) - gtt_offset;
> + ht.tail = stream->perf->ops.oa_hw_tail_read(stream) - gtt_offset;
> +
> + if (copy_to_user(output, &ht, sizeof(ht)))
> + return -EFAULT;
> +
> + return 0;
> +}
> +
> +#define I915_PERF_OA_BUFFER_MMAP_OFFSET 1
> +
> +/**
> + * i915_perf_oa_buffer_info_locked - size and offset of the OA buffer
> + * @stream: i915 perf stream
> + * @arg: pointer to oa buffer info filled by this function.
> + */
> +static int i915_perf_oa_buffer_info_locked(struct i915_perf_stream *stream,
> + unsigned long arg)
> +{
> + struct drm_i915_perf_oa_buffer_info info;
> + void __user *output = (void __user *)arg;
> +
> + if (i915_perf_stream_paranoid && !perfmon_capable()) {
> + DRM_DEBUG("Insufficient privileges to access OA buffer info\n");
> + return -EACCES;
> + }
> +
> + if (!output)
> + return -EINVAL;
> +
> + memset(&info, 0, sizeof(info));
> +
> + info.size = stream->oa_buffer.vma->size;
> + info.offset = I915_PERF_OA_BUFFER_MMAP_OFFSET * PAGE_SIZE;
> +
> + if (copy_to_user(output, &info, sizeof(info)))
> + return -EFAULT;
> +
> + return 0;
> +}
> +
> /**
> * i915_perf_ioctl - support ioctl() usage with i915 perf stream FDs
> * @stream: An i915 perf stream
> @@ -3239,6 +3347,10 @@ static long i915_perf_ioctl_locked(struct i915_perf_stream *stream,
> return 0;
> case I915_PERF_IOCTL_CONFIG:
> return i915_perf_config_locked(stream, arg);
> + case I915_PERF_IOCTL_GET_OA_BUFFER_INFO:
> + return i915_perf_oa_buffer_info_locked(stream, arg);
> + case I915_PERF_IOCTL_GET_OA_BUFFER_HEAD_TAIL:
> + return i915_perf_oa_buffer_head_tail_locked(stream, arg);
> }
>
> return -EINVAL;
> @@ -3291,7 +3403,8 @@ static void i915_perf_destroy_locked(struct i915_perf_stream *stream)
> if (stream->ctx)
> i915_gem_context_put(stream->ctx);
>
> - kfree(stream);
> + WRITE_ONCE(stream->closed, true);
> + perf_stream_put(stream);
> }
>
> /**
> @@ -3314,12 +3427,98 @@ static int i915_perf_release(struct inode *inode, struct file *file)
> i915_perf_destroy_locked(stream);
> mutex_unlock(&perf->lock);
>
> + unmap_mapping_range(file->f_mapping, 0, OA_BUFFER_SIZE, 1);
> +
> /* Release the reference the perf stream kept on the driver. */
> drm_dev_put(&perf->i915->drm);
>
> return 0;
> }
>
> +static void vm_open_oa(struct vm_area_struct *vma)
> +{
> + struct i915_perf_stream *stream = vma->vm_private_data;
> +
> + GEM_BUG_ON(!stream);
> + perf_stream_get(stream);
> +}
> +
> +static void vm_close_oa(struct vm_area_struct *vma)
> +{
> + struct i915_perf_stream *stream = vma->vm_private_data;
> +
> + GEM_BUG_ON(!stream);
> + perf_stream_put(stream);
> +}
> +
> +static vm_fault_t vm_fault_oa(struct vm_fault *vmf)
> +{
> + struct vm_area_struct *vma = vmf->vma;
> + struct i915_perf_stream *stream = vma->vm_private_data;
> + struct i915_perf *perf = stream->perf;
> + struct drm_i915_gem_object *obj = stream->oa_buffer.vma->obj;
I could be wrong because I'm not that knowledgeable on memory mapping stuff.
But it seems if close() is called on the i915-perf stream before this
function is called. stream->oa_buffer.vma might be NULL/freed.
It seems like we need an additional reference on the
stream->oa_buffer.vma->obj taken within the perf->lock in this function.
If you notice the stream->oa_buffer.vaddr is NULL inside the lock, it
means a close() call won the race with the mmap() and you should return
VM_FAULT_SIGBUS.
We should drop that reference taken on stream->oa_buffer.vma->obj when
the memory is unmapped.
Maybe Chris can confirm if that sounds correct.
-Lionel
> + int err;
> + bool closed;
> +
> + mutex_lock(&perf->lock);
> + closed = READ_ONCE(stream->closed);
> + mutex_unlock(&perf->lock);
> +
> + if (closed)
> + return VM_FAULT_SIGBUS;
> +
> + err = i915_gem_object_pin_pages(obj);
> + if (err)
> + goto out;
> +
> + err = remap_io_sg(vma,
> + vma->vm_start, vma->vm_end - vma->vm_start,
> + obj->mm.pages->sgl, -1);
> +
> + i915_gem_object_unpin_pages(obj);
> +
> +out:
> + return i915_error_to_vmf_fault(err);
> +}
> +
> +static const struct vm_operations_struct vm_ops_oa = {
> + .open = vm_open_oa,
> + .close = vm_close_oa,
> + .fault = vm_fault_oa,
> +};
> +
> +int i915_perf_mmap(struct file *file, struct vm_area_struct *vma)
> +{
> + struct i915_perf_stream *stream = file->private_data;
> +
> + if (i915_perf_stream_paranoid && !perfmon_capable()) {
> + DRM_DEBUG("Insufficient privileges to map OA buffer\n");
> + return -EACCES;
> + }
> +
> + switch (vma->vm_pgoff) {
> + case I915_PERF_OA_BUFFER_MMAP_OFFSET:
> + if (vma->vm_end - vma->vm_start > OA_BUFFER_SIZE)
> + return -EINVAL;
> +
> + if (vma->vm_flags & VM_WRITE)
> + return -EINVAL;
> +
> + break;
> +
> + default:
> + return -EINVAL;
> + }
> +
> + vma->vm_flags &= ~(VM_MAYWRITE | VM_MAYEXEC | VM_MAYSHARE);
> + vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
> + vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
> + vma->vm_private_data = stream;
> + vma->vm_ops = &vm_ops_oa;
> + vm_open_oa(vma);
> +
> + return 0;
> +}
>
> static const struct file_operations fops = {
> .owner = THIS_MODULE,
> @@ -3332,6 +3531,7 @@ static const struct file_operations fops = {
> * to handle 32bits compatibility.
> */
> .compat_ioctl = i915_perf_ioctl,
> + .mmap = i915_perf_mmap,
> };
>
>
> @@ -4260,6 +4460,7 @@ void i915_perf_init(struct drm_i915_private *i915)
> perf->ops.oa_disable = gen7_oa_disable;
> perf->ops.read = gen7_oa_read;
> perf->ops.oa_hw_tail_read = gen7_oa_hw_tail_read;
> + perf->ops.oa_hw_head_read = gen7_oa_hw_head_read;
>
> perf->oa_formats = hsw_oa_formats;
> } else if (HAS_LOGICAL_RING_CONTEXTS(i915)) {
> @@ -4291,6 +4492,7 @@ void i915_perf_init(struct drm_i915_private *i915)
> perf->ops.enable_metric_set = gen8_enable_metric_set;
> perf->ops.disable_metric_set = gen8_disable_metric_set;
> perf->ops.oa_hw_tail_read = gen8_oa_hw_tail_read;
> + perf->ops.oa_hw_head_read = gen8_oa_hw_head_read;
>
> if (IS_GEN(i915, 8)) {
> perf->ctx_oactxctrl_offset = 0x120;
> @@ -4318,6 +4520,7 @@ void i915_perf_init(struct drm_i915_private *i915)
> perf->ops.enable_metric_set = gen8_enable_metric_set;
> perf->ops.disable_metric_set = gen10_disable_metric_set;
> perf->ops.oa_hw_tail_read = gen8_oa_hw_tail_read;
> + perf->ops.oa_hw_head_read = gen8_oa_hw_head_read;
>
> if (IS_GEN(i915, 10)) {
> perf->ctx_oactxctrl_offset = 0x128;
> @@ -4342,6 +4545,7 @@ void i915_perf_init(struct drm_i915_private *i915)
> perf->ops.enable_metric_set = gen12_enable_metric_set;
> perf->ops.disable_metric_set = gen12_disable_metric_set;
> perf->ops.oa_hw_tail_read = gen12_oa_hw_tail_read;
> + perf->ops.oa_hw_head_read = gen12_oa_hw_head_read;
>
> perf->ctx_flexeu0_offset = 0;
> perf->ctx_oactxctrl_offset = 0x144;
> @@ -4456,8 +4660,11 @@ int i915_perf_ioctl_version(void)
> *
> * - OA buffer head/tail/status/buffer registers for read only
> * - OA counters A18, A19, A20 for read/write
> + *
> + * 8: Added an option to map oa buffer at umd driver level and trigger
> + * oa reports within oa buffer from command buffer.
> */
> - return 7;
> + return 8;
> }
>
> #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
> diff --git a/drivers/gpu/drm/i915/i915_perf_types.h b/drivers/gpu/drm/i915/i915_perf_types.h
> index a36a455ae336..2efbe35c5fa9 100644
> --- a/drivers/gpu/drm/i915/i915_perf_types.h
> +++ b/drivers/gpu/drm/i915/i915_perf_types.h
> @@ -311,6 +311,18 @@ struct i915_perf_stream {
> * buffer should be checked for available data.
> */
> u64 poll_oa_period;
> +
> + /**
> + * @closed: Open or closed state of the stream.
> + * True if stream is closed.
> + */
> + bool closed;
> +
> + /**
> + * @refcount: References to the mapped OA buffer managed by this
> + * stream.
> + */
> + struct kref refcount;
> };
>
> /**
> @@ -377,6 +389,11 @@ struct i915_oa_ops {
> * generations.
> */
> u32 (*oa_hw_tail_read)(struct i915_perf_stream *stream);
> +
> + /**
> + * @oa_hw_head_read: read the OA head pointer register
> + */
> + u32 (*oa_hw_head_read)(struct i915_perf_stream *stream);
> };
>
> struct i915_perf {
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 00546062e023..2042f6339182 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -2048,6 +2048,38 @@ struct drm_i915_perf_open_param {
> */
> #define I915_PERF_IOCTL_CONFIG _IO('i', 0x2)
>
> +/**
> + * Returns OA buffer properties to be used with mmap.
> + *
> + * This ioctl is available in perf revision 8.
> + */
> +#define I915_PERF_IOCTL_GET_OA_BUFFER_INFO _IO('i', 0x3)
> +
> +/**
> + * OA buffer size and offset.
> + */
> +struct drm_i915_perf_oa_buffer_info {
> + __u32 size;
> + __u32 offset;
> + __u64 reserved[4];
> +};
> +
> +/**
> + * Returns current position of OA buffer head and tail.
> + *
> + * This ioctl is available in perf revision 8.
> + */
> +#define I915_PERF_IOCTL_GET_OA_BUFFER_HEAD_TAIL _IO('i', 0x4)
> +
> +/**
> + * OA buffer head and tail.
> + */
> +struct drm_i915_perf_oa_buffer_head_tail {
> + __u32 head;
> + __u32 tail;
> + __u64 reserved[4];
> +};
> +
> /**
> * Common to all i915 perf records
> */
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