[Intel-gfx] [PATCH 8/8] drm/i915/perf: Map OA buffer to user space for gen12 performance query
Lionel Landwerlin
lionel.g.landwerlin at intel.com
Wed Nov 18 11:57:03 UTC 2020
Tests are on the IGT ml :
https://patchwork.freedesktop.org/series/82352/
<https://patchwork.freedesktop.org/series/82352/>
This feature was requested by the metrics-discovery team.
Pretty sure this was tested with it, maybe a branch can be shared by Piotr?
Cheers,
-Lionel
On 18/11/2020 13:41, Joonas Lahtinen wrote:
> + Umesh, Lionel
>
> Do we have a link to the userspace changes and IGT tests? Those are
> absolutely needed before we can do a final review and merge.
>
> We should really test and review the kernel and userspace changes
> together to make sure that we're coming up with a solid uAPI.
>
> Regards, Joonas
>
> Quoting Chris Wilson (2020-11-17 13:01:32)
>> From: Umesh Nerlige Ramappa <umesh.nerlige.ramappa 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)
>> v5:
>> - Strip access to OA buffer from unprivileged child of a privileged
>> parent. Use VM_DONTCOPY
>> - Enforce MAP_PRIVATE by checking for VM_MAYSHARE
>>
>> v6:
>> (Chris)
>> - Use len of -1 in unmap_mapping_range
>> - Don't use stream->oa_buffer.vma->obj in vm_fault_oa
>> - Use kernel block comment style
>> - do_mmap gets a reference to the file and puts it in do_munmap, so
>> no need to maintain a reference to i915_perf_stream. Hence, remove
>> vm_open/vm_close and stream->closed hooks/checks.
>> (Umesh)
>> - Do not allow mmap if SAMPLE_OA_REPORT is not set during
>> i915_perf_open_ioctl.
>> - Drop ioctl returning head/tail since this information is already
>> whitelisted. Remove hooks to read head register.
>>
>> v7: (Chris)
>> - unmap before destroy
>> - change ioctl argument struct
>>
>> v8: Documentation and more checks (Chris)
>>
>> Signed-off-by: Piotr Maciejewski <piotr.maciejewski at intel.com>
>> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
>> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
>> ---
>> 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 | 126 ++++++++++++++++++++++-
>> include/uapi/drm/i915_drm.h | 33 ++++++
>> 4 files changed, 161 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
>> index 3d69e51f3e4d..2ab08b152b9d 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 c91f2da84189..6fd669b520d8 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"
>> @@ -3291,6 +3293,44 @@ static long i915_perf_config_locked(struct i915_perf_stream *stream,
>> return ret;
>> }
>>
>> +#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
>> + * @cmd: ioctl command
>> + * @arg: pointer to oa buffer info filled by this function.
>> + */
>> +static int i915_perf_oa_buffer_info_locked(struct i915_perf_stream *stream,
>> + unsigned int cmd,
>> + 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 (_IOC_SIZE(cmd) != sizeof(info))
>> + return -EINVAL;
>> +
>> + if (copy_from_user(&info, output, sizeof(info)))
>> + return -EFAULT;
>> +
>> + if (info.type || info.flags || info.rsvd)
>> + return -EINVAL;
>> +
>> + 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_locked - support ioctl() usage with i915 perf stream FDs
>> * @stream: An i915 perf stream
>> @@ -3316,6 +3356,8 @@ 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, cmd, arg);
>> }
>>
>> return -EINVAL;
>> @@ -3387,6 +3429,14 @@ static int i915_perf_release(struct inode *inode, struct file *file)
>> struct i915_perf_stream *stream = file->private_data;
>> struct i915_perf *perf = stream->perf;
>>
>> + /*
>> + * User could have multiple vmas from multiple mmaps. We want to zap
>> + * them all here. Note that a fresh fault cannot occur as the mmap holds
>> + * a reference to the stream via the vma->vm_file, so before user's
>> + * munmap, the stream cannot be destroyed.
>> + */
>> + unmap_mapping_range(file->f_mapping, 0, -1, 1);
>> +
>> mutex_lock(&perf->lock);
>> i915_perf_destroy_locked(stream);
>> mutex_unlock(&perf->lock);
>> @@ -3397,6 +3447,75 @@ static int i915_perf_release(struct inode *inode, struct file *file)
>> return 0;
>> }
>>
>> +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;
>> + int err;
>> +
>> + err = remap_io_sg(vma,
>> + vma->vm_start, vma->vm_end - vma->vm_start,
>> + stream->oa_buffer.vma->pages->sgl, -1);
>> +
>> + return i915_error_to_vmf_fault(err);
>> +}
>> +
>> +static const struct vm_operations_struct vm_ops_oa = {
>> + .fault = vm_fault_oa,
>> +};
>> +
>> +static int i915_perf_mmap(struct file *file, struct vm_area_struct *vma)
>> +{
>> + struct i915_perf_stream *stream = file->private_data;
>> +
>> + /* mmap-ing OA buffer to user space MUST absolutely be privileged */
>> + if (i915_perf_stream_paranoid && !perfmon_capable()) {
>> + DRM_DEBUG("Insufficient privileges to map OA buffer\n");
>> + return -EACCES;
>> + }
>> +
>> + switch (vma->vm_pgoff) {
>> + /*
>> + * A non-zero offset ensures that we are mapping the right object. Also
>> + * leaves room for future objects added to this implementation.
>> + */
>> + case I915_PERF_OA_BUFFER_MMAP_OFFSET:
>> + if (!(stream->sample_flags & SAMPLE_OA_REPORT))
>> + return -EINVAL;
>> +
>> + if (vma->vm_end - vma->vm_start > OA_BUFFER_SIZE)
>> + return -EINVAL;
>> +
>> + /*
>> + * Only support VM_READ. Enforce MAP_PRIVATE by checking for
>> + * VM_MAYSHARE.
>> + */
>> + if (vma->vm_flags & (VM_WRITE | VM_EXEC |
>> + VM_SHARED | VM_MAYSHARE))
>> + return -EINVAL;
>> +
>> + vma->vm_flags &= ~(VM_MAYWRITE | VM_MAYEXEC);
>> +
>> + /*
>> + * If the privileged parent forks and child drops root
>> + * privilege, we do not want the child to retain access to the
>> + * mapped OA buffer. Explicitly set VM_DONTCOPY to avoid such
>> + * cases.
>> + */
>> + vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND |
>> + VM_DONTDUMP | VM_DONTCOPY;
>> + break;
>> +
>> + default:
>> + return -EINVAL;
>> + }
>> +
>> + vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
>> + vma->vm_private_data = stream;
>> + vma->vm_ops = &vm_ops_oa;
>> +
>> + return 0;
>> +}
>>
>> static const struct file_operations fops = {
>> .owner = THIS_MODULE,
>> @@ -3409,6 +3528,7 @@ static const struct file_operations fops = {
>> * to handle 32bits compatibility.
>> */
>> .compat_ioctl = i915_perf_ioctl,
>> + .mmap = i915_perf_mmap,
>> };
>>
>>
>> @@ -4559,8 +4679,12 @@ 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. See
>> + * I915_PERF_IOCTL_GET_OA_BUFFER_INFO.
>> */
>> - return 7;
>> + return 8;
>> }
>>
>> #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
>> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
>> index fa1f3d62f9a6..cc1702ddc859 100644
>> --- a/include/uapi/drm/i915_drm.h
>> +++ b/include/uapi/drm/i915_drm.h
>> @@ -2101,6 +2101,39 @@ 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 _IOWR('i', 0x3, struct drm_i915_perf_oa_buffer_info)
>> +
>> +/**
>> + * OA buffer size and offset.
>> + *
>> + * OA output buffer
>> + * type: 0
>> + * flags: mbz
>> + *
>> + * After querying the info, pass (size,offset) to mmap(),
>> + *
>> + * mmap(0, info.size, PROT_READ, MAP_PRIVATE, perf_fd, info.offset).
>> + *
>> + * Note that only a private (not shared between processes, or across fork())
>> + * read-only mmapping is allowed.
>> + *
>> + * Userspace must treat the incoming data as tainted, but it conforms to the OA
>> + * format as specified by user config. The buffer provides reports that have
>> + * OA counters - A, B and C.
>> + */
>> +struct drm_i915_perf_oa_buffer_info {
>> + __u32 type; /* in */
>> + __u32 flags; /* in */
>> + __u64 size; /* out */
>> + __u64 offset; /* out */
>> + __u64 rsvd; /* mbz */
>> +};
>> +
>> /**
>> * Common to all i915 perf records
>> */
>> --
>> 2.20.1
>>
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