Re: [Intel-gfx] [PATCH] drm/i915: Perf_limit_reasons are only available for Gen11+

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Mon, Sep 19, 2022 at 09:24:01AM -0700, Ashutosh Dixit wrote:
> Register GT0_PERF_LIMIT_REASONS (0x1381a8) is available only for
> Gen11+. Therefore ensure perf_limit_reasons sysfs/debugfs files are created
> only for Gen11+. Otherwise on Gen < 5 accessing these files results in the
> following oops:
> 
> <1> [88.829420] BUG: unable to handle page fault for address: ffffc90000bb81a8
> <1> [88.829438] #PF: supervisor read access in kernel mode
> <1> [88.829447] #PF: error_code(0x0000) - not-present page
> 
> Bspec: 20008
> Bug: https://gitlab.freedesktop.org/drm/intel/-/issues/6863
> Fixes: fe5979665f64 ("drm/i915/debugfs: Add perf_limit_reasons in debugfs")
> Fixes: fa68bff7cf27 ("drm/i915/gt: Add sysfs throttle frequency interfaces")
> Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_gt.c            |  4 ++++
>  drivers/gpu/drm/i915/gt/intel_gt_pm_debugfs.c | 10 +++++++++-
>  drivers/gpu/drm/i915/gt/intel_gt_sysfs_pm.c   | 15 +++++++++++----
>  3 files changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 5ddae95d4886..b367cfff48d5 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -233,6 +233,10 @@ static void gen6_clear_engine_error_register(struct intel_engine_cs *engine)
>  
>  i915_reg_t intel_gt_perf_limit_reasons_reg(struct intel_gt *gt)
>  {
> +	/* GT0_PERF_LIMIT_REASONS is available only for Gen11+ */
> +	if (GRAPHICS_VER(gt->i915) < 11)
> +		return INVALID_MMIO_REG;
> +
>  	return gt->type == GT_MEDIA ?
>  		MTL_MEDIA_PERF_LIMIT_REASONS : GT0_PERF_LIMIT_REASONS;
>  }
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm_debugfs.c b/drivers/gpu/drm/i915/gt/intel_gt_pm_debugfs.c
> index 68310881a793..10f680dbd7b6 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm_debugfs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm_debugfs.c
> @@ -682,6 +682,14 @@ static int perf_limit_reasons_clear(void *data, u64 val)
>  
>  	return 0;
>  }
> +
> +static bool perf_limit_reasons_eval(void *data)
> +{
> +	struct intel_gt *gt = data;
> +
> +	return i915_mmio_reg_valid(intel_gt_perf_limit_reasons_reg(gt));
> +}
> +
>  DEFINE_SIMPLE_ATTRIBUTE(perf_limit_reasons_fops, perf_limit_reasons_get,
>  			perf_limit_reasons_clear, "%llu\n");
>  
> @@ -694,7 +702,7 @@ void intel_gt_pm_debugfs_register(struct intel_gt *gt, struct dentry *root)
>  		{ "forcewake_user", &forcewake_user_fops, NULL},
>  		{ "llc", &llc_fops, llc_eval },
>  		{ "rps_boost", &rps_boost_fops, rps_eval },
> -		{ "perf_limit_reasons", &perf_limit_reasons_fops, NULL },
> +		{ "perf_limit_reasons", &perf_limit_reasons_fops, perf_limit_reasons_eval },
>  	};
>  
>  	intel_gt_debugfs_register_files(root, files, ARRAY_SIZE(files), gt);
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_sysfs_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_sysfs_pm.c
> index 54deae45d81f..904160952369 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_sysfs_pm.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_sysfs_pm.c
> @@ -545,8 +545,7 @@ static INTEL_GT_RPS_BOOL_ATTR_RO(throttle_reason_ratl, RATL_MASK);
>  static INTEL_GT_RPS_BOOL_ATTR_RO(throttle_reason_vr_thermalert, VR_THERMALERT_MASK);
>  static INTEL_GT_RPS_BOOL_ATTR_RO(throttle_reason_vr_tdc, VR_TDC_MASK);
>  
> -static const struct attribute *freq_attrs[] = {
> -	&dev_attr_punit_req_freq_mhz.attr,
> +static const struct attribute *throttle_reason_attrs[] = {
>  	&attr_throttle_reason_status.attr,
>  	&attr_throttle_reason_pl1.attr,
>  	&attr_throttle_reason_pl2.attr,
> @@ -791,12 +790,20 @@ void intel_gt_sysfs_pm_init(struct intel_gt *gt, struct kobject *kobj)
>  	if (!is_object_gt(kobj))
>  		return;
>  
> -	ret = sysfs_create_files(kobj, freq_attrs);
> +	ret = sysfs_create_file(kobj, &dev_attr_punit_req_freq_mhz.attr);
>  	if (ret)
>  		drm_warn(&gt->i915->drm,
> -			 "failed to create gt%u throttle sysfs files (%pe)",
> +			 "failed to create gt%u punit_req_freq_mhz sysfs (%pe)",
>  			 gt->info.id, ERR_PTR(ret));
>  
> +	if (i915_mmio_reg_valid(intel_gt_perf_limit_reasons_reg(gt))) {
> +		ret = sysfs_create_files(kobj, throttle_reason_attrs);
> +		if (ret)
> +			drm_warn(&gt->i915->drm,
> +				 "failed to create gt%u throttle sysfs files (%pe)",
> +				 gt->info.id, ERR_PTR(ret));
> +	}
> +
>  	if (HAS_MEDIA_RATIO_MODE(gt->i915) && intel_uc_uses_guc_slpc(&gt->uc)) {
>  		ret = sysfs_create_files(kobj, media_perf_power_attrs);
>  		if (ret)
> -- 
> 2.34.1
>