Re: [PATCH v16 3/7] drm/xe/guc: Add capture size check in GuC log buffer

["Teres Alexis, Alan Previn" <alan.previn.teres.alexis@intel.com>]

On Mon, 2024-08-19 at 19:11 -0700, Zhanjun Dong wrote:
> Capture-nodes generated by GuC are placed in the GuC capture ring
> buffer which is a sub-region of the larger Guc-Log-buffer.
> Add capture output size check before allocating the shared buffer.
> 
> Signed-off-by: Zhanjun Dong <zhanjun.dong@intel.com>
> 
alan:snip

> +static int guc_capture_output_size_est(struct xe_guc *guc)
> +{
> +       struct xe_gt *gt = guc_to_gt(guc);
> +       struct xe_hw_engine *hwe;
> +       enum xe_hw_engine_id id;
> +
> +       int capture_size = 0;
> +       size_t tmp = 0;
> +
> +       if (!guc->capture)
> +               return -ENODEV;
> +
> +       /*
> +        * If every single engine-instance suffered a failure in quick succession but
> +        * were all unrelated, then a burst of multiple error-capture events would dump
> +        * registers for every one engine instance, one at a time. In this case, GuC
> +        * would even dump the global-registers repeatedly.
> +        *
> +        * For each engine instance, there would be 1 x guc_state_capture_group_t output
> +        * followed by 3 x guc_state_capture_t lists. The latter is how the register
> +        * dumps are split across different register types (where the '3' are global vs class
> +        * vs instance).
> +        */
> +       for_each_hw_engine(hwe, gt, id) {
> +               enum guc_capture_list_class_type capture_class;
> +
> +               capture_class = xe_engine_class_to_guc_capture_class(hwe->class);
> +               capture_size += sizeof(struct guc_state_capture_group_header_t) +
> +                                        (3 * sizeof(struct guc_state_capture_header_t));
> +
> +               if (!guc_capture_getlistsize(guc, 0, GUC_STATE_CAPTURE_TYPE_GLOBAL,
> +                                            0, &tmp, true))
> +                       capture_size += tmp;
> +               if (!guc_capture_getlistsize(guc, 0, GUC_STATE_CAPTURE_TYPE_ENGINE_CLASS,
> +                                            capture_class, &tmp, true))
> +                       capture_size += tmp;
> +               /* Estimate steering register size for rcs/ccs */
> +               if (capture_class == GUC_CAPTURE_LIST_CLASS_RENDER_COMPUTE) {
> +                       int total = guc_capture_get_steer_reg_num(guc_to_xe(guc)) *
> +                                   XE_MAX_DSS_FUSE_BITS;
> +
> +                       capture_size += PAGE_ALIGN((sizeof(struct guc_debug_capture_list)) +
> +                                                  (total * sizeof(struct guc_mmio_reg)));
> +               }
alan: as per the review-conf-call last week, lets remove any traces of "steering register
size rules" from outside the guc_capture_getlistsize. As we know there are only 2 conditions
where we guc_capture_getlistsize can cause different results - one is when its called early
before pre-hwconfig and again if its called later after post-hwconfig. In both cases,
it doesn't matter who is making the call or the callstack, it will either need to 
return (at pre-hwconfig) the worst-case scenario where real-dss-masks were not yet available
and we use max-dss ... or (at post-hwconfig), where we can caclculate using real-dss-masks
and then get the valid value. That way, we don't need to care about "educating" other functions
about the differentiation between real-dss-masks being available or not, lets just always
ensure that the guc_capture_getlistsize always does this implicit decision for us so we dont
have to replicate such code in multiple place such as xe_guc_capture_ads_input_worst_size.

alan: actually just before hitting send button, i see you've addressed this in v17 (cleaning
both this code and the xe_guc_capture_ads_input_worst_size to remove this. I will drop further
review of v16 now and move to v17 or v18 if u wanna address those v16-nits i posted just now
quickly.
> +               if (!guc_capture_getlistsize(guc, 0, GUC_STATE_CAPTURE_TYPE_ENGINE_INSTANCE,
> +                                            capture_class, &tmp, true))
> +                       capture_size += tmp;
> +       }
> +
> +       return capture_size;
> +}
> +
> +/*
> + * Add on a 3x multiplier to allow for multiple back-to-back captures occurring
> + * before the Xe can read the data out and process it
> + */
> +#define GUC_CAPTURE_OVERBUFFER_MULTIPLIER 3
> +
> +static void check_guc_capture_size(struct xe_guc *guc)
> +{
> +       int capture_size = guc_capture_output_size_est(guc);
> +       int spare_size = capture_size * GUC_CAPTURE_OVERBUFFER_MULTIPLIER;
> +       u32 buffer_size = xe_guc_log_section_size_capture(&guc->log);
> +
> +       /*
> +        * NOTE: capture_size is much smaller than the capture region
> +        * allocation (DG2: <80K vs 1MB).
> +        * Additionally, its based on space needed to fit all engines getting
> +        * reset at once within the same G2H handler task slot. This is very
> +        * unlikely. However, if GuC really does run out of space for whatever
> +        * reason, we will see an separate warning message when processing the
> +        * G2H event capture-notification, search for:
> +        * xe_guc_STATE_CAPTURE_EVENT_STATUS_NOSPACE.
> +        */
> +       if (capture_size < 0)
> +               xe_gt_dbg(guc_to_gt(guc),
> +                         "Failed to calculate error state capture buffer minimum size: %d!\n",
> +                         capture_size);
> +       if (capture_size > buffer_size)
> +               xe_gt_dbg(guc_to_gt(guc), "Error state capture buffer maybe small: %d < %d\n",
> +                         buffer_size, capture_size);
> +       else if (spare_size > buffer_size)
> +               xe_gt_dbg(guc_to_gt(guc),
> +                         "Error state capture buffer lacks spare size: %d < %d (min = %d)\n",
> +                         buffer_size, spare_size, capture_size);
> +}
> +
>  /*
>   * xe_guc_capture_steered_list_init - Init steering register list
>   * @guc: The GuC object
> @@ -657,11 +745,12 @@ int xe_guc_capture_steered_list_init(struct xe_guc *guc)
>          * the end of the pre-populated render list.
>          */
>         guc_capture_alloc_steered_lists(guc);
> +       check_guc_capture_size(guc);
>  
>         return 0;
>  }
>  
> -/**
> +/*
>   * xe_guc_capture_init - Init for GuC register capture
>   * @guc: The GuC object
>   *
> diff --git a/drivers/gpu/drm/xe/xe_guc_log.c b/drivers/gpu/drm/xe/xe_guc_log.c
> index a37ee3419428..d6b5ac522b6c 100644
> --- a/drivers/gpu/drm/xe/xe_guc_log.c
> +++ b/drivers/gpu/drm/xe/xe_guc_log.c
> @@ -96,3 +96,68 @@ int xe_guc_log_init(struct xe_guc_log *log)
>  
>         return 0;
>  }
> +
> +static u32 xe_guc_log_section_size_crash(struct xe_guc_log *log)
> +{
> +       return CRASH_BUFFER_SIZE;
> +}
> +
> +static u32 xe_guc_log_section_size_debug(struct xe_guc_log *log)
> +{
> +       return DEBUG_BUFFER_SIZE;
> +}
> +
> +/**
> + * xe_guc_log_section_size_capture - Get capture buffer size within log sections.
> + * @log: The log object.
> + *
> + * This function will return the capture buffer size within log sections.
> + *
> + * Return: capture buffer size.
> + */
> +u32 xe_guc_log_section_size_capture(struct xe_guc_log *log)
> +{
> +       return CAPTURE_BUFFER_SIZE;
> +}
> +
> +/**
> + * xe_guc_get_log_buffer_size - Get log buffer size for a type.
> + * @log: The log object.
> + * @type: The log buffer type
> + *
> + * Return: buffer size.
> + */
> +u32 xe_guc_get_log_buffer_size(struct xe_guc_log *log, enum guc_log_buffer_type type)
> +{
> +       switch (type) {
> +       case GUC_LOG_BUFFER_CRASH_DUMP:
> +               return xe_guc_log_section_size_crash(log);
> +       case GUC_LOG_BUFFER_DEBUG:
> +               return xe_guc_log_section_size_debug(log);
> +       case GUC_LOG_BUFFER_CAPTURE:
> +               return xe_guc_log_section_size_capture(log);
> +       }
> +       return 0;
> +}
> +
> +/**
> + * xe_guc_get_log_buffer_offset - Get offset in log buffer for a type.
> + * @log: The log object.
> + * @type: The log buffer type
> + *
> + * This function will return the offset in the log buffer for a type.
> + * Return: buffer offset.
> + */
> +u32 xe_guc_get_log_buffer_offset(struct xe_guc_log *log, enum guc_log_buffer_type type)
> +{
> +       enum guc_log_buffer_type i;
> +       u32 offset = PAGE_SIZE;/* for the log_buffer_states */
> +
> +       for (i = GUC_LOG_BUFFER_CRASH_DUMP; i < GUC_LOG_BUFFER_TYPE_MAX; ++i) {
> +               if (i == type)
> +                       break;
> +               offset += xe_guc_get_log_buffer_size(log, i);
> +       }
> +
> +       return offset;
> +}
> diff --git a/drivers/gpu/drm/xe/xe_guc_log.h b/drivers/gpu/drm/xe/xe_guc_log.h
> index 2d25ab28b4b3..87ecd1814854 100644
> --- a/drivers/gpu/drm/xe/xe_guc_log.h
> +++ b/drivers/gpu/drm/xe/xe_guc_log.h
> @@ -7,6 +7,7 @@
>  #define _XE_GUC_LOG_H_
>  
>  #include "xe_guc_log_types.h"
> +#include "abi/guc_log_abi.h"
>  
>  struct drm_printer;
>  
> @@ -17,7 +18,7 @@ struct drm_printer;
>  #else
>  #define CRASH_BUFFER_SIZE      SZ_8K
>  #define DEBUG_BUFFER_SIZE      SZ_64K
> -#define CAPTURE_BUFFER_SIZE    SZ_16K
> +#define CAPTURE_BUFFER_SIZE    SZ_1M
>  #endif
>  /*
>   * While we're using plain log level in i915, GuC controls are much more...
> @@ -45,4 +46,8 @@ xe_guc_log_get_level(struct xe_guc_log *log)
>         return log->level;
>  }
>  
> +u32 xe_guc_log_section_size_capture(struct xe_guc_log *log);
> +u32 xe_guc_get_log_buffer_size(struct xe_guc_log *log, enum guc_log_buffer_type type);
> +u32 xe_guc_get_log_buffer_offset(struct xe_guc_log *log, enum guc_log_buffer_type type);
> +
>  #endif