From 5568638b4440a554d367881956b472a09485aa3d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>
Date: Wed, 2 Nov 2022 14:55:13 +0100
Subject: drm/amdgpu: workaround for TLB seq race
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Alt-commit: f9e69496450352fa0504fd5a8fd9134b31116558
Git-commit: 77c092e054262b594614bad5e5f47e57c5d29639
Patch-mainline: v6.1-rc5
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225 jsc#PED-2849
It can happen that we query the sequence value before the callback
had a chance to run.
Workaround that by grabbing the fence lock and releasing it again.
Should be replaced by hw handling soon.
Signed-off-by: Christian König <christian.koenig@amd.com>
CC: stable@vger.kernel.org # 5.19+
Fixes: 5255e146c99a6 ("drm/amdgpu: rework TLB flushing")
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2113
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Philip Yang <Philip.Yang@amd.com>
Tested-by: Stefan Springer <stefanspr94@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
index 83acb7bd80fe..1d31771b4230 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
@@ -492,6 +492,21 @@ void amdgpu_debugfs_vm_bo_info(struct amdgpu_vm *vm, struct seq_file *m);
*/
static inline uint64_t amdgpu_vm_tlb_seq(struct amdgpu_vm *vm)
{
+ unsigned long flags;
+ spinlock_t *lock;
+
+ /*
+ * Workaround to stop racing between the fence signaling and handling
+ * the cb. The lock is static after initially setting it up, just make
+ * sure that the dma_fence structure isn't freed up.
+ */
+ rcu_read_lock();
+ lock = vm->last_tlb_flush->lock;
+ rcu_read_unlock();
+
+ spin_lock_irqsave(lock, flags);
+ spin_unlock_irqrestore(lock, flags);
+
return atomic64_read(&vm->tlb_seq);
}
--
2.38.1