[Intel-gfx] [PATCH 4/4] drm/i915/perf: Map OA buffer to user space for gen12 performance query
Umesh Nerlige Ramappa
umesh.nerlige.ramappa at intel.com
Thu Jul 23 23:48:40 UTC 2020
On Thu, Jul 23, 2020 at 12:31:30PM +0300, Lionel Landwerlin wrote:
>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.
>
Based on trying to trigger a SIGBUS with igt, this is what I found:
do_mmap (somewhere in mmap_region) takes a reference to the file. If oa
buffer is mapped successfully, close(perf_fd) does not call
i915_perf_release, but close(perf_fd) followed by unmap() or vice-versa
will end up calling i915_perf_release.
forking did not help either because fork itself takes a reference to the
perf_fd.
Once unmap is called, the vma should be gone anyways, so I don't expect
the kernel to call vm_fault. I would say the kernel is really smart and
wouldn't let it happen :), but maybe Chris can confirm.
Thanks,
Umesh
>
>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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