[Intel-xe] [PATCH] drm/xe: Introduce xe_ASSERT macros

[Lucas De Marchi]

On Mon, Aug 07, 2023 at 07:34:46PM +0200, Michal Wajdeczko wrote:
>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 12.0 step B0
>    media: Xe_M 12.0 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
>
>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>
>---
> drivers/gpu/drm/xe/xe_assert.h | 160 +++++++++++++++++++++++++++++++++
> 1 file changed, 160 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..7ea295b7091c
>--- /dev/null
>+++ b/drivers/gpu/drm/xe/xe_assert.h
>@@ -0,0 +1,160 @@
>+/* 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 ASSERT macros that try to follow classic assert() utility and can be
>+ * compiled out on non-debug builds:
>+ *
>+ *  * &xe_ASSERT

pass by comment, not really checking anything else here... Why are we
mixing upper/lower case? It's perfectly fine to use XE_ as the namespace
like is done for other macros.

Lucas De Marchi