linux-kernel - [PATCH 4.19 12/16] drm/i915: Ensure intel_engine_init

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Date:   Fri,  6 Aug 2021 10:15:03 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stephen Boyd <swboyd@...omium.org>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Jani Nikula <jani.nikula@...el.com>
Subject: [PATCH 4.19 12/16] drm/i915: Ensure intel_engine_init_execlist() builds with Clang

From: Jani Nikula <jani.nikula@...el.com>

commit 410ed5731a6566498a3aa904420aa2e49ba0ba90 upstream.

Clang build with UBSAN enabled leads to the following build error:

drivers/gpu/drm/i915/intel_engine_cs.o: In function `intel_engine_init_execlist':
drivers/gpu/drm/i915/intel_engine_cs.c:411: undefined reference to `__compiletime_assert_411'

Again, for this to work the code would first need to be inlined and then
constant folded, which doesn't work for Clang because semantic analysis
happens before optimization/inlining.

Use GEM_BUG_ON() instead of BUILD_BUG_ON().

v2: Use is_power_of_2() from log2.h (Chris)

Reported-by: Stephen Boyd <swboyd@...omium.org>
Cc: Stephen Boyd <swboyd@...omium.org>
Cc: Chris Wilson <chris@...is-wilson.co.uk>
Tested-by: Nathan Chancellor <natechancellor@...il.com>
Tested-by: Stephen Boyd <swboyd@...omium.org>
Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181016122938.18757-2-jani.nikula@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/i915/intel_engine_cs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -463,7 +463,7 @@ static void intel_engine_init_execlist(s
 	struct intel_engine_execlists * const execlists = &engine->execlists;
 
 	execlists->port_mask = 1;
-	BUILD_BUG_ON_NOT_POWER_OF_2(execlists_num_ports(execlists));
+	GEM_BUG_ON(!is_power_of_2(execlists_num_ports(execlists)));
 	GEM_BUG_ON(execlists_num_ports(execlists) > EXECLIST_MAX_PORTS);
 
 	execlists->queue_priority = INT_MIN;