[PATCH v15 1/1] drm/i915: Allow user to set cache at BO creation
Andi Shyti
andi.shyti at linux.intel.com
Sun Jun 4 18:44:52 UTC 2023
Hi Fei,
On Wed, May 31, 2023 at 10:10:08AM -0700, fei.yang at intel.com wrote:
> From: Fei Yang <fei.yang at intel.com>
>
> To comply with the design that buffer objects shall have immutable
> cache setting through out their life cycle, {set, get}_caching ioctl's
> are no longer supported from MTL onward. With that change caching
> policy can only be set at object creation time. The current code
> applies a default (platform dependent) cache setting for all objects.
> However this is not optimal for performance tuning. The patch extends
> the existing gem_create uAPI to let user set PAT index for the object
> at creation time.
> The new extension is platform independent, so UMD's can switch to using
> this extension for older platforms as well, while {set, get}_caching are
> still supported on these legacy paltforms for compatibility reason.
>
> Note: The detailed description of PAT index is missing in current PRM
> even for older hardware and will be added by the next PRM update under
> chapter name "Memory Views".
Documentation has been updated:
https://www.intel.com/content/www/us/en/docs/graphics-for-linux/developer-reference/1-0/tiger-lake.html
If it's OK with you, before pushing I can replace this Note with:
"
The documentation related to the PAT/MOCS tables is currently
available for Tiger Lake here:
https://www.intel.com/content/www/us/en/docs/graphics-for-linux/developer-reference/1-0/tiger-lake.html
"
Thank you Tvrtko for the intution you had about the documentation
and for pushing for the update. It is greate to have this uAPI
well documented!
Andi
> BSpec: 45101
>
> Mesa support has been submitted in this merge request:
> https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22878
>
> The media driver is supported by the following commits:
> https://github.com/intel/media-driver/commit/92c00a857433ebb34ec575e9834f473c6fcb6341
> https://github.com/intel/media-driver/commit/fd375cf2c5e1f6bf6b43258ff797b3134aadc9fd
> https://github.com/intel/media-driver/commit/08dd244b22484770a33464c2c8ae85430e548000
>
> The IGT test related to this change is
> igt at gem_create@create-ext-set-pat
>
> Signed-off-by: Fei Yang <fei.yang at intel.com>
> Cc: Chris Wilson <chris.p.wilson at linux.intel.com>
> Cc: Matt Roper <matthew.d.roper at intel.com>
> Cc: Andi Shyti <andi.shyti at linux.intel.com>
> Reviewed-by: Andi Shyti <andi.shyti at linux.intel.com>
> Acked-by: Jordan Justen <jordan.l.justen at intel.com>
> Tested-by: Jordan Justen <jordan.l.justen at intel.com>
> Acked-by: Carl Zhang <carl.zhang at intel.com>
> Tested-by: Lihao Gu <lihao.gu at intel.com>
> ---
> drivers/gpu/drm/i915/gem/i915_gem_create.c | 36 +++++++++++++++++++
> drivers/gpu/drm/i915/gem/i915_gem_object.c | 6 ++++
> include/uapi/drm/i915_drm.h | 41 ++++++++++++++++++++++
> 3 files changed, 83 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_create.c b/drivers/gpu/drm/i915/gem/i915_gem_create.c
> index bfe1dbda4cb7..644a936248ad 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_create.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_create.c
> @@ -245,6 +245,7 @@ struct create_ext {
> unsigned int n_placements;
> unsigned int placement_mask;
> unsigned long flags;
> + unsigned int pat_index;
> };
>
> static void repr_placements(char *buf, size_t size,
> @@ -394,11 +395,39 @@ static int ext_set_protected(struct i915_user_extension __user *base, void *data
> return 0;
> }
>
> +static int ext_set_pat(struct i915_user_extension __user *base, void *data)
> +{
> + struct create_ext *ext_data = data;
> + struct drm_i915_private *i915 = ext_data->i915;
> + struct drm_i915_gem_create_ext_set_pat ext;
> + unsigned int max_pat_index;
> +
> + BUILD_BUG_ON(sizeof(struct drm_i915_gem_create_ext_set_pat) !=
> + offsetofend(struct drm_i915_gem_create_ext_set_pat, rsvd));
> +
> + if (copy_from_user(&ext, base, sizeof(ext)))
> + return -EFAULT;
> +
> + max_pat_index = INTEL_INFO(i915)->max_pat_index;
> +
> + if (ext.pat_index > max_pat_index) {
> + drm_dbg(&i915->drm, "PAT index is invalid: %u\n",
> + ext.pat_index);
> + return -EINVAL;
> + }
> +
> + ext_data->pat_index = ext.pat_index;
> +
> + return 0;
> +}
> +
> static const i915_user_extension_fn create_extensions[] = {
> [I915_GEM_CREATE_EXT_MEMORY_REGIONS] = ext_set_placements,
> [I915_GEM_CREATE_EXT_PROTECTED_CONTENT] = ext_set_protected,
> + [I915_GEM_CREATE_EXT_SET_PAT] = ext_set_pat,
> };
>
> +#define PAT_INDEX_NOT_SET 0xffff
> /**
> * i915_gem_create_ext_ioctl - Creates a new mm object and returns a handle to it.
> * @dev: drm device pointer
> @@ -418,6 +447,7 @@ i915_gem_create_ext_ioctl(struct drm_device *dev, void *data,
> if (args->flags & ~I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS)
> return -EINVAL;
>
> + ext_data.pat_index = PAT_INDEX_NOT_SET;
> ret = i915_user_extensions(u64_to_user_ptr(args->extensions),
> create_extensions,
> ARRAY_SIZE(create_extensions),
> @@ -454,5 +484,11 @@ i915_gem_create_ext_ioctl(struct drm_device *dev, void *data,
> if (IS_ERR(obj))
> return PTR_ERR(obj);
>
> + if (ext_data.pat_index != PAT_INDEX_NOT_SET) {
> + i915_gem_object_set_pat_index(obj, ext_data.pat_index);
> + /* Mark pat_index is set by UMD */
> + obj->pat_set_by_user = true;
> + }
> +
> return i915_gem_publish(obj, file, &args->size, &args->handle);
> }
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> index 46a19b099ec8..97ac6fb37958 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> @@ -208,6 +208,12 @@ bool i915_gem_object_can_bypass_llc(struct drm_i915_gem_object *obj)
> if (!(obj->flags & I915_BO_ALLOC_USER))
> return false;
>
> + /*
> + * Always flush cache for UMD objects at creation time.
> + */
> + if (obj->pat_set_by_user)
> + return true;
> +
> /*
> * EHL and JSL add the 'Bypass LLC' MOCS entry, which should make it
> * possible for userspace to bypass the GTT caching bits set by the
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index f31dfacde601..4083a23e0614 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -3679,9 +3679,13 @@ struct drm_i915_gem_create_ext {
> *
> * For I915_GEM_CREATE_EXT_PROTECTED_CONTENT usage see
> * struct drm_i915_gem_create_ext_protected_content.
> + *
> + * For I915_GEM_CREATE_EXT_SET_PAT usage see
> + * struct drm_i915_gem_create_ext_set_pat.
> */
> #define I915_GEM_CREATE_EXT_MEMORY_REGIONS 0
> #define I915_GEM_CREATE_EXT_PROTECTED_CONTENT 1
> +#define I915_GEM_CREATE_EXT_SET_PAT 2
> __u64 extensions;
> };
>
> @@ -3796,6 +3800,43 @@ struct drm_i915_gem_create_ext_protected_content {
> __u32 flags;
> };
>
> +/**
> + * struct drm_i915_gem_create_ext_set_pat - The
> + * I915_GEM_CREATE_EXT_SET_PAT extension.
> + *
> + * If this extension is provided, the specified caching policy (PAT index) is
> + * applied to the buffer object.
> + *
> + * Below is an example on how to create an object with specific caching policy:
> + *
> + * .. code-block:: C
> + *
> + * struct drm_i915_gem_create_ext_set_pat set_pat_ext = {
> + * .base = { .name = I915_GEM_CREATE_EXT_SET_PAT },
> + * .pat_index = 0,
> + * };
> + * struct drm_i915_gem_create_ext create_ext = {
> + * .size = PAGE_SIZE,
> + * .extensions = (uintptr_t)&set_pat_ext,
> + * };
> + *
> + * int err = ioctl(fd, DRM_IOCTL_I915_GEM_CREATE_EXT, &create_ext);
> + * if (err) ...
> + */
> +struct drm_i915_gem_create_ext_set_pat {
> + /** @base: Extension link. See struct i915_user_extension. */
> + struct i915_user_extension base;
> + /**
> + * @pat_index: PAT index to be set
> + * PAT index is a bit field in Page Table Entry to control caching
> + * behaviors for GPU accesses. The definition of PAT index is
> + * platform dependent and can be found in hardware specifications,
> + */
> + __u32 pat_index;
> + /** @rsvd: reserved for future use */
> + __u32 rsvd;
> +};
> +
> /* ID of the protected content session managed by i915 when PXP is active */
> #define I915_PROTECTED_CONTENT_DEFAULT_SESSION 0xf
>
> --
> 2.25.1
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