--- /dev/null
+From dc0297f3198bd60108ccbd167ee5d9fa4af31ed0 Mon Sep 17 00:00:00 2001
+From: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
+Date: Fri, 14 Feb 2025 14:22:17 +0530
+Subject: drm/amdgpu: Replace Mutex with Spinlock for RLCG register access to avoid Priority Inversion in SRIOV
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+From: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
+
+commit dc0297f3198bd60108ccbd167ee5d9fa4af31ed0 upstream.
+
+RLCG Register Access is a way for virtual functions to safely access GPU
+registers in a virtualized environment., including TLB flushes and
+register reads. When multiple threads or VFs try to access the same
+registers simultaneously, it can lead to race conditions. By using the
+RLCG interface, the driver can serialize access to the registers. This
+means that only one thread can access the registers at a time,
+preventing conflicts and ensuring that operations are performed
+correctly. Additionally, when a low-priority task holds a mutex that a
+high-priority task needs, ie., If a thread holding a spinlock tries to
+acquire a mutex, it can lead to priority inversion. register access in
+amdgpu_virt_rlcg_reg_rw especially in a fast code path is critical.
+
+The call stack shows that the function amdgpu_virt_rlcg_reg_rw is being
+called, which attempts to acquire the mutex. This function is invoked
+from amdgpu_sriov_wreg, which in turn is called from
+gmc_v11_0_flush_gpu_tlb.
+
+The [ BUG: Invalid wait context ] indicates that a thread is trying to
+acquire a mutex while it is in a context that does not allow it to sleep
+(like holding a spinlock).
+
+Fixes the below:
+
+[ 253.013423] =============================
+[ 253.013434] [ BUG: Invalid wait context ]
+[ 253.013446] 6.12.0-amdstaging-drm-next-lol-050225 #14 Tainted: G U OE
+[ 253.013464] -----------------------------
+[ 253.013475] kworker/0:1/10 is trying to lock:
+[ 253.013487] ffff9f30542e3cf8 (&adev->virt.rlcg_reg_lock){+.+.}-{3:3}, at: amdgpu_virt_rlcg_reg_rw+0xf6/0x330 [amdgpu]
+[ 253.013815] other info that might help us debug this:
+[ 253.013827] context-{4:4}
+[ 253.013835] 3 locks held by kworker/0:1/10:
+[ 253.013847] #0: ffff9f3040050f58 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x3f5/0x680
+[ 253.013877] #1: ffffb789c008be40 ((work_completion)(&wfc.work)){+.+.}-{0:0}, at: process_one_work+0x1d6/0x680
+[ 253.013905] #2: ffff9f3054281838 (&adev->gmc.invalidate_lock){+.+.}-{2:2}, at: gmc_v11_0_flush_gpu_tlb+0x198/0x4f0 [amdgpu]
+[ 253.014154] stack backtrace:
+[ 253.014164] CPU: 0 UID: 0 PID: 10 Comm: kworker/0:1 Tainted: G U OE 6.12.0-amdstaging-drm-next-lol-050225 #14
+[ 253.014189] Tainted: [U]=USER, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
+[ 253.014203] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 11/18/2024
+[ 253.014224] Workqueue: events work_for_cpu_fn
+[ 253.014241] Call Trace:
+[ 253.014250] <TASK>
+[ 253.014260] dump_stack_lvl+0x9b/0xf0
+[ 253.014275] dump_stack+0x10/0x20
+[ 253.014287] __lock_acquire+0xa47/0x2810
+[ 253.014303] ? srso_alias_return_thunk+0x5/0xfbef5
+[ 253.014321] lock_acquire+0xd1/0x300
+[ 253.014333] ? amdgpu_virt_rlcg_reg_rw+0xf6/0x330 [amdgpu]
+[ 253.014562] ? __lock_acquire+0xa6b/0x2810
+[ 253.014578] __mutex_lock+0x85/0xe20
+[ 253.014591] ? amdgpu_virt_rlcg_reg_rw+0xf6/0x330 [amdgpu]
+[ 253.014782] ? sched_clock_noinstr+0x9/0x10
+[ 253.014795] ? srso_alias_return_thunk+0x5/0xfbef5
+[ 253.014808] ? local_clock_noinstr+0xe/0xc0
+[ 253.014822] ? amdgpu_virt_rlcg_reg_rw+0xf6/0x330 [amdgpu]
+[ 253.015012] ? srso_alias_return_thunk+0x5/0xfbef5
+[ 253.015029] mutex_lock_nested+0x1b/0x30
+[ 253.015044] ? mutex_lock_nested+0x1b/0x30
+[ 253.015057] amdgpu_virt_rlcg_reg_rw+0xf6/0x330 [amdgpu]
+[ 253.015249] amdgpu_sriov_wreg+0xc5/0xd0 [amdgpu]
+[ 253.015435] gmc_v11_0_flush_gpu_tlb+0x44b/0x4f0 [amdgpu]
+[ 253.015667] gfx_v11_0_hw_init+0x499/0x29c0 [amdgpu]
+[ 253.015901] ? __pfx_smu_v13_0_update_pcie_parameters+0x10/0x10 [amdgpu]
+[ 253.016159] ? srso_alias_return_thunk+0x5/0xfbef5
+[ 253.016173] ? smu_hw_init+0x18d/0x300 [amdgpu]
+[ 253.016403] amdgpu_device_init+0x29ad/0x36a0 [amdgpu]
+[ 253.016614] amdgpu_driver_load_kms+0x1a/0xc0 [amdgpu]
+[ 253.017057] amdgpu_pci_probe+0x1c2/0x660 [amdgpu]
+[ 253.017493] local_pci_probe+0x4b/0xb0
+[ 253.017746] work_for_cpu_fn+0x1a/0x30
+[ 253.017995] process_one_work+0x21e/0x680
+[ 253.018248] worker_thread+0x190/0x330
+[ 253.018500] ? __pfx_worker_thread+0x10/0x10
+[ 253.018746] kthread+0xe7/0x120
+[ 253.018988] ? __pfx_kthread+0x10/0x10
+[ 253.019231] ret_from_fork+0x3c/0x60
+[ 253.019468] ? __pfx_kthread+0x10/0x10
+[ 253.019701] ret_from_fork_asm+0x1a/0x30
+[ 253.019939] </TASK>
+
+v2: s/spin_trylock/spin_lock_irqsave to be safe (Christian).
+
+Fixes: e864180ee49b ("drm/amdgpu: Add lock around VF RLCG interface")
+Cc: lin cao <lin.cao@amd.com>
+Cc: Jingwen Chen <Jingwen.Chen2@amd.com>
+Cc: Victor Skvortsov <victor.skvortsov@amd.com>
+Cc: Zhigang Luo <zhigang.luo@amd.com>
+Cc: Christian König <christian.koenig@amd.com>
+Cc: Alex Deucher <alexander.deucher@amd.com>
+Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
+Suggested-by: Alex Deucher <alexander.deucher@amd.com>
+Reviewed-by: Christian König <christian.koenig@amd.com>
+Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
+[ Minor context change fixed. ]
+Signed-off-by: Wenshan Lan <jetlan9@163.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
+ drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c | 5 +++--
+ drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h | 3 ++-
+ 3 files changed, 6 insertions(+), 4 deletions(-)
+
+--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
++++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+@@ -4144,7 +4144,6 @@ int amdgpu_device_init(struct amdgpu_dev
+ mutex_init(&adev->grbm_idx_mutex);
+ mutex_init(&adev->mn_lock);
+ mutex_init(&adev->virt.vf_errors.lock);
+- mutex_init(&adev->virt.rlcg_reg_lock);
+ hash_init(adev->mn_hash);
+ mutex_init(&adev->psp.mutex);
+ mutex_init(&adev->notifier_lock);
+@@ -4170,6 +4169,7 @@ int amdgpu_device_init(struct amdgpu_dev
+ spin_lock_init(&adev->se_cac_idx_lock);
+ spin_lock_init(&adev->audio_endpt_idx_lock);
+ spin_lock_init(&adev->mm_stats.lock);
++ spin_lock_init(&adev->virt.rlcg_reg_lock);
+ spin_lock_init(&adev->wb.lock);
+
+ INIT_LIST_HEAD(&adev->reset_list);
+--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c
++++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c
+@@ -1010,6 +1010,7 @@ u32 amdgpu_virt_rlcg_reg_rw(struct amdgp
+ void *scratch_reg2;
+ void *scratch_reg3;
+ void *spare_int;
++ unsigned long flags;
+
+ if (!adev->gfx.rlc.rlcg_reg_access_supported) {
+ dev_err(adev->dev,
+@@ -1031,7 +1032,7 @@ u32 amdgpu_virt_rlcg_reg_rw(struct amdgp
+ scratch_reg2 = (void __iomem *)adev->rmmio + 4 * reg_access_ctrl->scratch_reg2;
+ scratch_reg3 = (void __iomem *)adev->rmmio + 4 * reg_access_ctrl->scratch_reg3;
+
+- mutex_lock(&adev->virt.rlcg_reg_lock);
++ spin_lock_irqsave(&adev->virt.rlcg_reg_lock, flags);
+
+ if (reg_access_ctrl->spare_int)
+ spare_int = (void __iomem *)adev->rmmio + 4 * reg_access_ctrl->spare_int;
+@@ -1090,7 +1091,7 @@ u32 amdgpu_virt_rlcg_reg_rw(struct amdgp
+
+ ret = readl(scratch_reg0);
+
+- mutex_unlock(&adev->virt.rlcg_reg_lock);
++ spin_unlock_irqrestore(&adev->virt.rlcg_reg_lock, flags);
+
+ return ret;
+ }
+--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h
++++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h
+@@ -275,7 +275,8 @@ struct amdgpu_virt {
+ /* the ucode id to signal the autoload */
+ uint32_t autoload_ucode_id;
+
+- struct mutex rlcg_reg_lock;
++ /* Spinlock to protect access to the RLCG register interface */
++ spinlock_t rlcg_reg_lock;
+ };
+
+ struct amdgpu_video_codec_info;
projects / thirdparty / kernel / stable-queue.git / commitdiff
