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> Hi Fei,
>
> On Wed, May 31, 2023 at 10:10:08AM -0700, fei.yang@xxxxxxxxx wrote:
>> From: Fei Yang <fei.yang@xxxxxxxxx>
>>
>> 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
>"
Looks good to me. Thank you Andi and Tvrtko for all your help.
-Fei
>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@gem_create@create-ext-set-pat
>>
>> Signed-off-by: Fei Yang <fei.yang@xxxxxxxxx>
>> Cc: Chris Wilson <chris.p.wilson@xxxxxxxxxxxxxxx>
>> Cc: Matt Roper <matthew.d.roper@xxxxxxxxx>
>> Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
>> Reviewed-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
>> Acked-by: Jordan Justen <jordan.l.justen@xxxxxxxxx>
>> Tested-by: Jordan Justen <jordan.l.justen@xxxxxxxxx>
>> Acked-by: Carl Zhang <carl.zhang@xxxxxxxxx>
>> Tested-by: Lihao Gu <lihao.gu@xxxxxxxxx>
>> ---
>> 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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