[Intel-xe] [PATCH v4 2/3] drm/xe: Introduce Xe assert macros
Michal Wajdeczko
michal.wajdeczko at intel.com
Tue Sep 12 13:18:23 UTC 2023
On 12.09.2023 13:35, Jani Nikula wrote:
> On Tue, 12 Sep 2023, Francois Dugast <francois.dugast at intel.com> wrote:
>> From: Michal Wajdeczko <michal.wajdeczko at intel.com>
>>
>> As we are moving away from the controversial XE_BUG_ON macro,
>> relying just on WARN_ON or drm_err does not cover the cases
>> where we want to annotate functions with additional detailed
>> debug checks to assert that all prerequisites are satisfied,
>> without paying footprint or performance penalty on non-debug
>> builds, where all misuses introduced during code integration
>> were already fixed.
>>
>> Introduce family of Xe assert macros that try to follow classic
>> assert() utility and can be compiled out on non-debug builds.
>>
>> Macros are based on drm_WARN, but unlikely to origin, disallow
>> use in expressions since we will compile that code out.
>>
>> As we are operating on the xe pointers, we can print additional
>> information about the device, like tile or GT identifier, that
>> is not available from generic WARN report:
>>
>> [ ] xe 0000:00:02.0: [drm] Assertion `true == false` failed!
>> platform: 1 subplatform: 1
>> graphics: Xe_LP 12.00 step B0
>> media: Xe_M 12.00 step B0
>> display: enabled step D0
>> tile: 0 VRAM 0 B
>> GT: 0 type 1
>>
>> [ ] xe 0000:b3:00.0: [drm] Assertion `true == false` failed!
>> platform: 7 subplatform: 3
>> graphics: Xe_HPG 12.55 step A1
>> media: Xe_HPM 12.55 step A1
>> display: disabled step **
>> tile: 0 VRAM 14.0 GiB
>> GT: 0 type 1
>>
>> [ ] WARNING: CPU: 0 PID: 2687 at drivers/gpu/drm/xe/xe_device.c:281 xe_device_probe+0x374/0x520 [xe]
>> [ ] RIP: 0010:xe_device_probe+0x374/0x520 [xe]
>> [ ] Call Trace:
>> [ ] ? __warn+0x7b/0x160
>> [ ] ? xe_device_probe+0x374/0x520 [xe]
>> [ ] ? report_bug+0x1c3/0x1d0
>> [ ] ? handle_bug+0x42/0x70
>> [ ] ? exc_invalid_op+0x14/0x70
>> [ ] ? asm_exc_invalid_op+0x16/0x20
>> [ ] ? xe_device_probe+0x374/0x520 [xe]
>> [ ] ? xe_device_probe+0x374/0x520 [xe]
>> [ ] xe_pci_probe+0x6e3/0x950 [xe]
>> [ ] ? lockdep_hardirqs_on+0xc7/0x140
>> [ ] pci_device_probe+0x9e/0x160
>> [ ] really_probe+0x19d/0x400
>>
>> v2: use lowercase names
>> v3: apply xe coding style
>>
>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
>> Cc: Oded Gabbay <ogabbay at kernel.org>
>> Cc: Jani Nikula <jani.nikula at intel.com>
>> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
>> Cc: Matthew Brost <matthew.brost at intel.com>
>> Cc: Lucas De Marchi <lucas.demarchi at intel.com>
>> Cc: Matt Roper <matthew.d.roper at intel.com>
>> Reviewed-by: Lucas De Marchi <lucas.demarchi at intel.com>
>> Acked-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
>> ---
>> drivers/gpu/drm/xe/xe_assert.h | 177 +++++++++++++++++++++++++++++++++
>> 1 file changed, 177 insertions(+)
>> create mode 100644 drivers/gpu/drm/xe/xe_assert.h
>>
>> diff --git a/drivers/gpu/drm/xe/xe_assert.h b/drivers/gpu/drm/xe/xe_assert.h
>> new file mode 100644
>> index 000000000000..b2d3c9b82b31
>> --- /dev/null
>> +++ b/drivers/gpu/drm/xe/xe_assert.h
>> @@ -0,0 +1,177 @@
>> +/* SPDX-License-Identifier: MIT */
>> +/*
>> + * Copyright © 2023 Intel Corporation
>> + */
>> +
>> +#ifndef _XE_ASSERT_H_
>> +#define _XE_ASSERT_H_
>> +
>> +#include <linux/string_helpers.h>
>> +
>> +#include <drm/drm_print.h>
>> +
>> +#include "xe_device_types.h"
>> +#include "xe_step.h"
>> +
>> +/**
>> + * DOC: Xe ASSERTs
>> + *
>> + * While Xe driver aims to be simpler than legacy i915 driver it is still
>> + * complex enough that some changes introduced while adding new functionality
>> + * could break the existing code.
>> + *
>> + * Adding &drm_WARN or &drm_err to catch unwanted programming usage could lead
>> + * to undesired increased driver footprint and may impact production driver
>> + * performance as this additional code will be always present.
>> + *
>> + * To allow annotate functions with additional detailed debug checks to assert
>> + * that all prerequisites are satisfied, without worrying about footprint or
>> + * performance penalty on production builds where all potential misuses
>> + * introduced during code integration were already fixed, we introduce family
>> + * of Xe assert macros that try to follow classic assert() utility:
>> + *
>> + * * &xe_assert
>> + * * &xe_tile_assert
>> + * * &xe_gt_assert
>> + *
>> + * These macros are implemented on top of &drm_WARN, but unlikely to the origin,
>> + * warning is triggered when provided condition is false. Additionally all above
>> + * assert macros cannot be used in expressions or as a condition, since
>> + * underlying code will be compiled out on non-debug builds.
>> + *
>> + * Note that these macros are not intended for use to cover known gaps in the
>> + * implementation; for such cases use regular &drm_WARN or &drm_err and provide
>> + * valid safe fallback.
>> + *
>> + * Also in cases where performance or footprint is not an issue, developers
>> + * should continue to use the regular &drm_WARN or &drm_err to ensure that bug
>> + * reports from production builds will contain meagningful diagnostics data.
>> + *
>> + * Below code shows how asserts could help in debug to catch unplanned use::
>> + *
>> + * static void one_igfx(struct xe_device *xe)
>> + * {
>> + * xe_assert(xe, xe->info.is_dgfx == false);
>> + * xe_assert(xe, xe->info.tile_count == 1);
>> + * }
>> + *
>> + * static void two_dgfx(struct xe_device *xe)
>> + * {
>> + * xe_assert(xe, xe->info.is_dgfx);
>> + * xe_assert(xe, xe->info.tile_count == 2);
>> + * }
>> + *
>> + * void foo(struct xe_device *xe)
>> + * {
>> + * if (xe->info.dgfx)
>> + * return two_dgfx(xe);
>> + * return one_igfx(xe);
>> + * }
>> + *
>> + * void bar(struct xe_device *xe)
>> + * {
>> + * if (drm_WARN_ON(xe->drm, xe->info.tile_count > 2))
>> + * return;
>> + *
>> + * if (xe->info.tile_count == 2)
>> + * return two_dgfx(xe);
>> + * return one_igfx(xe);
>> + * }
>> + */
>> +
>> +#if IS_ENABLED(CONFIG_DRM_XE_DEBUG)
>> +#define __xe_assert_msg(xe, condition, msg, arg...) ({ \
>> + (void)drm_WARN(&(xe)->drm, !(condition), "[" DRM_NAME "] Assertion `%s` failed!\n" msg, \
>> + __stringify(condition), ## arg); \
>> +})
>> +#else
>> +#define __xe_assert_msg(xe, condition, msg, arg...) ({ \
>> + typecheck(struct xe_device *, xe); \
>> + BUILD_BUG_ON_INVALID(condition); \
>> +})
>> +#endif
>> +
>> +/**
>> + * xe_assert - warn if condition is false when debugging.
>> + * @xe: the &struct xe_device pointer to which &condition applies
>> + * @condition: condition to check
>> + *
>> + * xe_assert() uses &drm_WARN to emit a warning and print additional information
>> + * that could be read from the &xe pointer if provided &condition is false.
>> + *
>> + * Contrary to &drm_WARN, xe_assert() is effective only on debug builds
>> + * (&CONFIG_DRM_XE_DEBUG must be enabled) and cannot be used in expressions
>> + * or as a condition.
>> + *
>> + * See `Xe ASSERTs`_ for general usage guidelines.
>> + */
>> +#define xe_assert(xe, condition) xe_assert_msg((xe), condition, "")
>> +#define xe_assert_msg(xe, condition, msg, arg...) ({ \
>> + struct xe_device *__xe = (xe); \
>> + __xe_assert_msg(__xe, condition, \
>> + "platform: %d subplatform: %d\n" \
>> + "graphics: %s %u.%02u step %s\n" \
>> + "media: %s %u.%02u step %s\n" \
>> + "display: %s step %s\n" \
>> + msg, \
>> + __xe->info.platform, __xe->info.subplatform, \
>> + __xe->info.graphics_name, \
>> + __xe->info.graphics_verx100 / 100, \
>> + __xe->info.graphics_verx100 % 100, \
>> + xe_step_name(__xe->info.step.graphics), \
>> + __xe->info.media_name, \
>> + __xe->info.media_verx100 / 100, \
>> + __xe->info.media_verx100 % 100, \
>> + xe_step_name(__xe->info.step.media), \
>> + str_enabled_disabled(__xe->info.enable_display), \
>> + xe_step_name(__xe->info.step.display), \
>> + ## arg); \
>> +})
>
> I guess I have missed this huge splat all along... Why is it necessary?
> If you print the device id, all the information should be there already,
> right?
somewhere in the dmesg (if someone/CI was clever enough) maybe yes
but in bug reports usually only the WARN is included, so exposing some
basic info here for quicker triage
>
> This also makes it impossible to use xe_assert() with a NULL xe device
> pointer in contexts where you don't have the device available.
there was no such requirement (but we can add that if needed)
note that code is based on drm_WARN() which also doesn't work with NULL
Michal
>
> BR,
> Jani.
>
>
>> +
>> +/**
>> + * xe_tile_assert - warn if condition is false when debugging.
>> + * @tile: the &struct xe_tile pointer to which &condition applies
>> + * @condition: condition to check
>> + *
>> + * xe_tile_assert() uses &drm_WARN to emit a warning and print additional
>> + * information that could be read from the &tile pointer if provided &condition
>> + * is false.
>> + *
>> + * Contrary to &drm_WARN, xe_tile_assert() is effective only on debug builds
>> + * (&CONFIG_DRM_XE_DEBUG must be enabled) and cannot be used in expressions
>> + * or as a condition.
>> + *
>> + * See `Xe ASSERTs`_ for general usage guidelines.
>> + */
>> +#define xe_tile_assert(tile, condition) xe_tile_assert_msg((tile), condition, "")
>> +#define xe_tile_assert_msg(tile, condition, msg, arg...) ({ \
>> + struct xe_tile *__tile = (tile); \
>> + char __buf[10]; \
>> + xe_assert_msg(tile_to_xe(__tile), condition, "tile: %u VRAM %s\n" msg, \
>> + __tile->id, ({ string_get_size(__tile->mem.vram.actual_physical_size, 1, \
>> + STRING_UNITS_2, __buf, sizeof(__buf)); __buf; }), ## arg); \
>> +})
>> +
>> +/**
>> + * xe_gt_assert - warn if condition is false when debugging.
>> + * @gt: the &struct xe_gt pointer to which &condition applies
>> + * @condition: condition to check
>> + *
>> + * xe_gt_assert() uses &drm_WARN to emit a warning and print additional
>> + * information that could be safetely read from the > pointer if provided
>> + * &condition is false.
>> + *
>> + * Contrary to &drm_WARN, xe_gt_assert() is effective only on debug builds
>> + * (&CONFIG_DRM_XE_DEBUG must be enabled) and cannot be used in expressions
>> + * or as a condition.
>> + *
>> + * See `Xe ASSERTs`_ for general usage guidelines.
>> + */
>> +#define xe_gt_assert(gt, condition) xe_gt_assert_msg((gt), condition, "")
>> +#define xe_gt_assert_msg(gt, condition, msg, arg...) ({ \
>> + struct xe_gt *__gt = (gt); \
>> + xe_tile_assert_msg(gt_to_tile(__gt), condition, "GT: %u type %d\n" msg, \
>> + __gt->info.id, __gt->info.type, ## arg); \
>> +})
>> +
>> +#endif
>
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