From f88cb1bbdc1fd9a70e9768d0310fd2d4792a53ee Mon Sep 17 00:00:00 2001
From: Jani Nikula <jani.nikula@intel.com>
Date: Tue, 1 Aug 2023 15:32:50 +0300
Subject: drm/i915/uncore: fix race around i915->params.mmio_debug
Git-commit: d823445b09a2f1c43877b87a55fc699c3a836fc2
Patch-mainline: v6.6-rc1
References: jsc#PED-3527 jsc#PED-5475 jsc#PED-6068 jsc#PED-6070 jsc#PED-6116 jsc#PED-6120 jsc#PED-5065 jsc#PED-5477 jsc#PED-5511 jsc#PED-6041 jsc#PED-6069 jsc#PED-6071

Only check the conditions for unclaimed reg debug once to avoid locking
problems when i915->params.mmio_debug changes between header and footer.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8749
Cc: Lee Shawn C <shawn.c.lee@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/a53fb0fd84c4627398ccd4304b35db05603b89b6.1690886109.git.jani.nikula@intel.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/i915/intel_uncore.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index a88aa342b623..dfefad5a5fec 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1925,27 +1925,26 @@ __unclaimed_previous_reg_debug(struct intel_uncore *uncore,
 			i915_mmio_reg_offset(reg));
 }
 
-static inline void
+static inline bool __must_check
 unclaimed_reg_debug_header(struct intel_uncore *uncore,
 			   const i915_reg_t reg, const bool read)
 {
 	if (likely(!uncore->i915->params.mmio_debug) || !uncore->debug)
-		return;
+		return false;
 
 	/* interrupts are disabled and re-enabled around uncore->lock usage */
 	lockdep_assert_held(&uncore->lock);
 
 	spin_lock(&uncore->debug->lock);
 	__unclaimed_previous_reg_debug(uncore, reg, read);
+
+	return true;
 }
 
 static inline void
 unclaimed_reg_debug_footer(struct intel_uncore *uncore,
 			   const i915_reg_t reg, const bool read)
 {
-	if (likely(!uncore->i915->params.mmio_debug) || !uncore->debug)
-		return;
-
 	/* interrupts are disabled and re-enabled around uncore->lock usage */
 	lockdep_assert_held(&uncore->lock);
 
@@ -2008,13 +2007,15 @@ __gen2_read(64)
 #define GEN6_READ_HEADER(x) \
 	u32 offset = i915_mmio_reg_offset(reg); \
 	unsigned long irqflags; \
+	bool unclaimed_reg_debug; \
 	u##x val = 0; \
 	assert_rpm_wakelock_held(uncore->rpm); \
 	spin_lock_irqsave(&uncore->lock, irqflags); \
-	unclaimed_reg_debug_header(uncore, reg, true)
+	unclaimed_reg_debug = unclaimed_reg_debug_header(uncore, reg, true)
 
 #define GEN6_READ_FOOTER \
-	unclaimed_reg_debug_footer(uncore, reg, true); \
+	if (unclaimed_reg_debug) \
+		unclaimed_reg_debug_footer(uncore, reg, true);	\
 	spin_unlock_irqrestore(&uncore->lock, irqflags); \
 	trace_i915_reg_rw(false, reg, val, sizeof(val), trace); \
 	return val
@@ -2112,13 +2113,15 @@ __gen2_write(32)
 #define GEN6_WRITE_HEADER \
 	u32 offset = i915_mmio_reg_offset(reg); \
 	unsigned long irqflags; \
+	bool unclaimed_reg_debug; \
 	trace_i915_reg_rw(true, reg, val, sizeof(val), trace); \
 	assert_rpm_wakelock_held(uncore->rpm); \
 	spin_lock_irqsave(&uncore->lock, irqflags); \
-	unclaimed_reg_debug_header(uncore, reg, false)
+	unclaimed_reg_debug = unclaimed_reg_debug_header(uncore, reg, false)
 
 #define GEN6_WRITE_FOOTER \
-	unclaimed_reg_debug_footer(uncore, reg, false); \
+	if (unclaimed_reg_debug) \
+		unclaimed_reg_debug_footer(uncore, reg, false); \
 	spin_unlock_irqrestore(&uncore->lock, irqflags)
 
 #define __gen6_write(x) \
-- 
2.43.0