This patch fixes lockdep issue due to circular locking dependency of
struct_mutex, i_mutex_key, mmap_sem, relay_channels_mutex.
For GuC log relay channel we create debugfs file that requires i_mutex_key
lock and we are doing that under struct_mutex. So we introduced newer
dependency as:
    &dev->struct_mutex --> &sb->s_type->i_mutex_key#3 --> &mm->mmap_sem
However, there is dependency from mmap_sem to struct_mutex. Hence we
separate the relay create/destroy operation from under struct_mutex.

======================================================
WARNING: possible circular locking dependency detected
4.15.0-rc6-CI-Patchwork_7614+ #1 Not tainted
------------------------------------------------------
debugfs_test/1388 is trying to acquire lock:
 (&dev->struct_mutex){+.+.}, at: [<00000000d5e1d915>] 
i915_mutex_lock_interruptible+0x47/0x130 [i915]

but task is already holding lock:
 (&mm->mmap_sem){++++}, at: [<0000000029a9c131>] __do_page_fault+0x106/0x560

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (&mm->mmap_sem){++++}:
       _copy_to_user+0x1e/0x70
       filldir+0x8c/0xf0
       dcache_readdir+0xeb/0x160
       iterate_dir+0xdc/0x140
       SyS_getdents+0xa0/0x130
       entry_SYSCALL_64_fastpath+0x1c/0x89

-> #2 (&sb->s_type->i_mutex_key#3){++++}:
       start_creating+0x59/0x110
       __debugfs_create_file+0x2e/0xe0
       relay_create_buf_file+0x62/0x80
       relay_late_setup_files+0x84/0x250
       guc_log_late_setup+0x4f/0x110 [i915]
       i915_guc_log_register+0x32/0x40 [i915]
       i915_driver_load+0x7b6/0x1720 [i915]
       i915_pci_probe+0x2e/0x90 [i915]
       pci_device_probe+0x9c/0x120
       driver_probe_device+0x2a3/0x480
       __driver_attach+0xd9/0xe0
       bus_for_each_dev+0x57/0x90
       bus_add_driver+0x168/0x260
       driver_register+0x52/0xc0
       do_one_initcall+0x39/0x150
       do_init_module+0x56/0x1ef
       load_module+0x231c/0x2d70
       SyS_finit_module+0xa5/0xe0
       entry_SYSCALL_64_fastpath+0x1c/0x89

-> #1 (relay_channels_mutex){+.+.}:
       relay_open+0x12c/0x2b0
       intel_guc_log_runtime_create+0xab/0x230 [i915]
       intel_guc_init+0x81/0x120 [i915]
       intel_uc_init+0x29/0xa0 [i915]
       i915_gem_init+0x182/0x530 [i915]
       i915_driver_load+0xaa9/0x1720 [i915]
       i915_pci_probe+0x2e/0x90 [i915]
       pci_device_probe+0x9c/0x120
       driver_probe_device+0x2a3/0x480
       __driver_attach+0xd9/0xe0
       bus_for_each_dev+0x57/0x90
       bus_add_driver+0x168/0x260
       driver_register+0x52/0xc0
       do_one_initcall+0x39/0x150
       do_init_module+0x56/0x1ef
       load_module+0x231c/0x2d70
       SyS_finit_module+0xa5/0xe0
       entry_SYSCALL_64_fastpath+0x1c/0x89

-> #0 (&dev->struct_mutex){+.+.}:
       __mutex_lock+0x81/0x9b0
       i915_mutex_lock_interruptible+0x47/0x130 [i915]
       i915_gem_fault+0x201/0x790 [i915]
       __do_fault+0x15/0x70
       __handle_mm_fault+0x677/0xdc0
       handle_mm_fault+0x14f/0x2f0
       __do_page_fault+0x2d1/0x560
       page_fault+0x4c/0x60

other info that might help us debug this:

Chain exists of:
  &dev->struct_mutex --> &sb->s_type->i_mutex_key#3 --> &mm->mmap_sem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&mm->mmap_sem);
                               lock(&sb->s_type->i_mutex_key#3);
                               lock(&mm->mmap_sem);
  lock(&dev->struct_mutex);

 *** DEADLOCK ***

1 lock held by debugfs_test/1388:
 #0:  (&mm->mmap_sem){++++}, at: [<0000000029a9c131>] 
__do_page_fault+0x106/0x560

stack backtrace:
CPU: 2 PID: 1388 Comm: debugfs_test Not tainted 4.15.0-rc6-CI-Patchwork_7614+ #1
Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./J4205-ITX, BIOS 
P1.10 09/29/2016
Call Trace:
 dump_stack+0x5f/0x86
 print_circular_bug.isra.18+0x1d0/0x2c0
 __lock_acquire+0x14ae/0x1b60
 ? lock_acquire+0xaf/0x200
 lock_acquire+0xaf/0x200
 ? i915_mutex_lock_interruptible+0x47/0x130 [i915]
 __mutex_lock+0x81/0x9b0
 ? i915_mutex_lock_interruptible+0x47/0x130 [i915]
 ? i915_mutex_lock_interruptible+0x47/0x130 [i915]
 ? i915_mutex_lock_interruptible+0x47/0x130 [i915]
 i915_mutex_lock_interruptible+0x47/0x130 [i915]
 ? __pm_runtime_resume+0x4f/0x80
 i915_gem_fault+0x201/0x790 [i915]
 __do_fault+0x15/0x70
 ? _raw_spin_unlock+0x29/0x40
 __handle_mm_fault+0x677/0xdc0
 handle_mm_fault+0x14f/0x2f0
 __do_page_fault+0x2d1/0x560
 ? page_fault+0x36/0x60
 page_fault+0x4c/0x60

v2: Added lock protection to guc->log.runtime.relay_chan (Chris)
    Fixed locking inside guc_flush_logs uncovered by new lockdep.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104693
Testcase: igt/debugfs_test/read_all_entries # with enable_guc=1 and 
guc_log_level=1
Signed-off-by: Sagar Arun Kamble <sagar.a.kam...@intel.com>
Cc: Michal Wajdeczko <michal.wajdec...@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospu...@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
Cc: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
Cc: Marta Lofstedt <marta.lofst...@intel.com>
Cc: Michal Winiarski <michal.winiar...@intel.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c  |  12 +--
 drivers/gpu/drm/i915/i915_drv.c      |   2 +-
 drivers/gpu/drm/i915/i915_gem.c      |   4 +-
 drivers/gpu/drm/i915/intel_guc.c     |   7 +-
 drivers/gpu/drm/i915/intel_guc_log.c | 140 ++++++++++++++++++++++++++++-------
 drivers/gpu/drm/i915/intel_guc_log.h |  11 +++
 drivers/gpu/drm/i915/intel_uc.c      |  31 ++++++--
 drivers/gpu/drm/i915/intel_uc.h      |   4 +-
 8 files changed, 161 insertions(+), 50 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c 
b/drivers/gpu/drm/i915/i915_debugfs.c
index 80dc679..b45be0d 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2467,7 +2467,6 @@ static int i915_guc_log_control_get(void *data, u64 *val)
 static int i915_guc_log_control_set(void *data, u64 val)
 {
        struct drm_i915_private *dev_priv = data;
-       int ret;
 
        if (!HAS_GUC(dev_priv))
                return -ENODEV;
@@ -2475,16 +2474,7 @@ static int i915_guc_log_control_set(void *data, u64 val)
        if (!dev_priv->guc.log.vma)
                return -EINVAL;
 
-       ret = mutex_lock_interruptible(&dev_priv->drm.struct_mutex);
-       if (ret)
-               return ret;
-
-       intel_runtime_pm_get(dev_priv);
-       ret = i915_guc_log_control(dev_priv, val);
-       intel_runtime_pm_put(dev_priv);
-
-       mutex_unlock(&dev_priv->drm.struct_mutex);
-       return ret;
+       return i915_guc_log_control(dev_priv, val);
 }
 
 DEFINE_SIMPLE_ATTRIBUTE(i915_guc_log_control_fops,
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 1fbe378..29048b9 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -626,7 +626,7 @@ static void i915_gem_fini(struct drm_i915_private *dev_priv)
        i915_gem_contexts_fini(dev_priv);
        mutex_unlock(&dev_priv->drm.struct_mutex);
 
-       intel_uc_fini_wq(dev_priv);
+       intel_uc_fini_misc(dev_priv);
        i915_gem_cleanup_userptr(dev_priv);
 
        i915_gem_drain_freed_objects(dev_priv);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 7f0684c..34d0d51 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5193,7 +5193,7 @@ int i915_gem_init(struct drm_i915_private *dev_priv)
        if (ret)
                return ret;
 
-       ret = intel_uc_init_wq(dev_priv);
+       ret = intel_uc_init_misc(dev_priv);
        if (ret)
                return ret;
 
@@ -5289,7 +5289,7 @@ int i915_gem_init(struct drm_i915_private *dev_priv)
        intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
        mutex_unlock(&dev_priv->drm.struct_mutex);
 
-       intel_uc_fini_wq(dev_priv);
+       intel_uc_fini_misc(dev_priv);
 
        if (ret != -EIO)
                i915_gem_cleanup_userptr(dev_priv);
diff --git a/drivers/gpu/drm/i915/intel_guc.c b/drivers/gpu/drm/i915/intel_guc.c
index ea30e7c..cab3c98 100644
--- a/drivers/gpu/drm/i915/intel_guc.c
+++ b/drivers/gpu/drm/i915/intel_guc.c
@@ -66,6 +66,7 @@ void intel_guc_init_early(struct intel_guc *guc)
        intel_guc_ct_init_early(&guc->ct);
 
        mutex_init(&guc->send_mutex);
+       mutex_init(&guc->log.runtime.relay_lock);
        guc->send = intel_guc_send_nop;
        guc->notify = gen8_guc_raise_irq;
 }
@@ -87,8 +88,10 @@ int intel_guc_init_wq(struct intel_guc *guc)
         */
        guc->log.runtime.flush_wq = alloc_ordered_workqueue("i915-guc_log",
                                                WQ_HIGHPRI | WQ_FREEZABLE);
-       if (!guc->log.runtime.flush_wq)
+       if (!guc->log.runtime.flush_wq) {
+               DRM_ERROR("Couldn't allocate workqueue for GuC log\n");
                return -ENOMEM;
+       }
 
        /*
         * Even though both sending GuC action, and adding a new workitem to
@@ -109,6 +112,8 @@ int intel_guc_init_wq(struct intel_guc *guc)
                                                          WQ_HIGHPRI);
                if (!guc->preempt_wq) {
                        destroy_workqueue(guc->log.runtime.flush_wq);
+                       DRM_ERROR("Couldn't allocate workqueue for GuC "
+                                 "preemption\n");
                        return -ENOMEM;
                }
        }
diff --git a/drivers/gpu/drm/i915/intel_guc_log.c 
b/drivers/gpu/drm/i915/intel_guc_log.c
index 2ffc966..573d96d 100644
--- a/drivers/gpu/drm/i915/intel_guc_log.c
+++ b/drivers/gpu/drm/i915/intel_guc_log.c
@@ -181,6 +181,13 @@ static int guc_log_relay_file_create(struct intel_guc *guc)
        return 0;
 }
 
+static bool guc_log_has_relay(struct intel_guc *guc)
+{
+       lockdep_assert_held(&guc->log.runtime.relay_lock);
+
+       return guc->log.runtime.relay_chan != NULL;
+}
+
 static void guc_move_to_next_buf(struct intel_guc *guc)
 {
        /* Make sure the updates made in the sub buffer are visible when
@@ -188,6 +195,9 @@ static void guc_move_to_next_buf(struct intel_guc *guc)
         */
        smp_wmb();
 
+       if (!guc_log_has_relay(guc))
+               return;
+
        /* All data has been written, so now move the offset of sub buffer. */
        relay_reserve(guc->log.runtime.relay_chan, 
guc->log.vma->obj->base.size);
 
@@ -197,7 +207,7 @@ static void guc_move_to_next_buf(struct intel_guc *guc)
 
 static void *guc_get_write_buffer(struct intel_guc *guc)
 {
-       if (!guc->log.runtime.relay_chan)
+       if (!guc_log_has_relay(guc))
                return NULL;
 
        /* Just get the base address of a new sub buffer and copy data into it
@@ -266,7 +276,9 @@ static void guc_read_update_log_buffer(struct intel_guc 
*guc)
        log_buf_state = src_data = guc->log.runtime.buf_addr;
 
        /* Get the pointer to local buffer to store the logs */
+       mutex_lock(&guc->log.runtime.relay_lock);
        log_buf_snapshot_state = dst_data = guc_get_write_buffer(guc);
+       mutex_unlock(&guc->log.runtime.relay_lock);
 
        /* Actual logs are present from the 2nd page */
        src_data += PAGE_SIZE;
@@ -335,6 +347,7 @@ static void guc_read_update_log_buffer(struct intel_guc 
*guc)
                dst_data += buffer_size;
        }
 
+       mutex_lock(&guc->log.runtime.relay_lock);
        if (log_buf_snapshot_state)
                guc_move_to_next_buf(guc);
        else {
@@ -344,6 +357,7 @@ static void guc_read_update_log_buffer(struct intel_guc 
*guc)
                DRM_ERROR_RATELIMITED("no sub-buffer to capture logs\n");
                guc->log.capture_miss_count++;
        }
+       mutex_unlock(&guc->log.runtime.relay_lock);
 }
 
 static void capture_logs_work(struct work_struct *work)
@@ -363,12 +377,12 @@ static int guc_log_runtime_create(struct intel_guc *guc)
 {
        struct drm_i915_private *dev_priv = guc_to_i915(guc);
        void *vaddr;
-       struct rchan *guc_log_relay_chan;
-       size_t n_subbufs, subbuf_size;
        int ret;
 
        lockdep_assert_held(&dev_priv->drm.struct_mutex);
 
+       GEM_BUG_ON(!guc_log_has_relay(guc));
+
        GEM_BUG_ON(guc_log_has_runtime(guc));
 
        ret = i915_gem_object_set_to_wc_domain(guc->log.vma->obj, true);
@@ -387,8 +401,40 @@ static int guc_log_runtime_create(struct intel_guc *guc)
 
        guc->log.runtime.buf_addr = vaddr;
 
+       INIT_WORK(&guc->log.runtime.flush_work, capture_logs_work);
+
+       return 0;
+}
+
+static void guc_log_runtime_destroy(struct intel_guc *guc)
+{
+       /*
+        * It's possible that the runtime stuff was never allocated because
+        * GuC log was disabled at the boot time.
+        **/
+       if (!guc_log_has_runtime(guc))
+               return;
+
+       i915_gem_object_unpin_map(guc->log.vma->obj);
+       guc->log.runtime.buf_addr = NULL;
+}
+
+int intel_guc_log_relay_create(struct intel_guc *guc)
+{
+       struct drm_i915_private *dev_priv = guc_to_i915(guc);
+       struct rchan *guc_log_relay_chan;
+       size_t n_subbufs, subbuf_size;
+       int ret;
+
+       if (!i915_modparams.guc_log_level)
+               return 0;
+
+       lockdep_assert_held(&guc->log.runtime.relay_lock);
+
+       GEM_BUG_ON(guc_log_has_relay(guc));
+
         /* Keep the size of sub buffers same as shared log buffer */
-       subbuf_size = guc->log.vma->obj->base.size;
+       subbuf_size = GUC_LOG_SIZE;
 
        /* Store up to 8 snapshots, which is large enough to buffer sufficient
         * boot time logs and provides enough leeway to User, in terms of
@@ -407,33 +453,33 @@ static int guc_log_runtime_create(struct intel_guc *guc)
                DRM_ERROR("Couldn't create relay chan for GuC logging\n");
 
                ret = -ENOMEM;
-               goto err_vaddr;
+               goto err;
        }
 
        GEM_BUG_ON(guc_log_relay_chan->subbuf_size < subbuf_size);
        guc->log.runtime.relay_chan = guc_log_relay_chan;
 
-       INIT_WORK(&guc->log.runtime.flush_work, capture_logs_work);
        return 0;
 
-err_vaddr:
-       i915_gem_object_unpin_map(guc->log.vma->obj);
-       guc->log.runtime.buf_addr = NULL;
+err:
+       /* logging will be off */
+       i915_modparams.guc_log_level = 0;
        return ret;
 }
 
-static void guc_log_runtime_destroy(struct intel_guc *guc)
+void intel_guc_log_relay_destroy(struct intel_guc *guc)
 {
+       lockdep_assert_held(&guc->log.runtime.relay_lock);
+
        /*
-        * It's possible that the runtime stuff was never allocated because
+        * It's possible that the relay was never allocated because
         * GuC log was disabled at the boot time.
         */
-       if (!guc_log_has_runtime(guc))
+       if (!guc_log_has_relay(guc))
                return;
 
        relay_close(guc->log.runtime.relay_chan);
-       i915_gem_object_unpin_map(guc->log.vma->obj);
-       guc->log.runtime.buf_addr = NULL;
+       guc->log.runtime.relay_chan = NULL;
 }
 
 static int guc_log_late_setup(struct intel_guc *guc)
@@ -441,27 +487,48 @@ static int guc_log_late_setup(struct intel_guc *guc)
        struct drm_i915_private *dev_priv = guc_to_i915(guc);
        int ret;
 
-       lockdep_assert_held(&dev_priv->drm.struct_mutex);
-
        if (!guc_log_has_runtime(guc)) {
                /*
                 * If log was disabled at boot time, then setup needed to handle
                 * log buffer flush interrupts would not have been done yet, so
                 * do that now.
                 */
-               ret = guc_log_runtime_create(guc);
+               GEM_BUG_ON(guc_log_has_relay(guc));
+
+               mutex_lock(&guc->log.runtime.relay_lock);
+               ret = intel_guc_log_relay_create(guc);
+               mutex_unlock(&guc->log.runtime.relay_lock);
+
                if (ret)
                        goto err;
+
+               mutex_lock(&dev_priv->drm.struct_mutex);
+               intel_runtime_pm_get(dev_priv);
+               ret = guc_log_runtime_create(guc);
+               intel_runtime_pm_put(dev_priv);
+               mutex_unlock(&dev_priv->drm.struct_mutex);
+
+               if (ret)
+                       goto err_relay;
        }
 
+       mutex_lock(&guc->log.runtime.relay_lock);
        ret = guc_log_relay_file_create(guc);
+       mutex_unlock(&guc->log.runtime.relay_lock);
+
        if (ret)
                goto err_runtime;
 
        return 0;
 
 err_runtime:
+       mutex_lock(&dev_priv->drm.struct_mutex);
        guc_log_runtime_destroy(guc);
+       mutex_unlock(&dev_priv->drm.struct_mutex);
+err_relay:
+       mutex_lock(&guc->log.runtime.relay_lock);
+       intel_guc_log_relay_destroy(guc);
+       mutex_unlock(&guc->log.runtime.relay_lock);
 err:
        /* logging will remain off */
        i915_modparams.guc_log_level = 0;
@@ -490,7 +557,11 @@ static void guc_flush_logs(struct intel_guc *guc)
                return;
 
        /* First disable the interrupts, will be renabled afterwards */
+       mutex_lock(&dev_priv->drm.struct_mutex);
+       intel_runtime_pm_get(dev_priv);
        gen9_disable_guc_interrupts(dev_priv);
+       intel_runtime_pm_put(dev_priv);
+       mutex_unlock(&dev_priv->drm.struct_mutex);
 
        /* Before initiating the forceful flush, wait for any pending/ongoing
         * flush to complete otherwise forceful flush may not actually happen.
@@ -498,7 +569,11 @@ static void guc_flush_logs(struct intel_guc *guc)
        flush_work(&guc->log.runtime.flush_work);
 
        /* Ask GuC to update the log buffer state */
+       mutex_lock(&dev_priv->drm.struct_mutex);
+       intel_runtime_pm_get(dev_priv);
        guc_log_flush(guc);
+       intel_runtime_pm_put(dev_priv);
+       mutex_unlock(&dev_priv->drm.struct_mutex);
 
        /* GuC would have updated log buffer by now, so capture it */
        guc_log_capture_logs(guc);
@@ -509,17 +584,10 @@ int intel_guc_log_create(struct intel_guc *guc)
        struct i915_vma *vma;
        unsigned long offset;
        u32 flags;
-       u32 size;
        int ret;
 
        GEM_BUG_ON(guc->log.vma);
 
-       /* The first page is to save log buffer state. Allocate one
-        * extra page for others in case for overlap */
-       size = (1 + GUC_LOG_DPC_PAGES + 1 +
-               GUC_LOG_ISR_PAGES + 1 +
-               GUC_LOG_CRASH_PAGES + 1) << PAGE_SHIFT;
-
        /* We require SSE 4.1 for fast reads from the GuC log buffer and
         * it should be present on the chipsets supporting GuC based
         * submisssions.
@@ -529,7 +597,7 @@ int intel_guc_log_create(struct intel_guc *guc)
                goto err;
        }
 
-       vma = intel_guc_allocate_vma(guc, size);
+       vma = intel_guc_allocate_vma(guc, GUC_LOG_SIZE);
        if (IS_ERR(vma)) {
                ret = PTR_ERR(vma);
                goto err;
@@ -584,7 +652,15 @@ int i915_guc_log_control(struct drm_i915_private 
*dev_priv, u64 control_val)
                return 0;
 
        verbosity = enable_logging ? control_val - 1 : 0;
+
+       ret = mutex_lock_interruptible(&dev_priv->drm.struct_mutex);
+       if (ret)
+               return ret;
+       intel_runtime_pm_get(dev_priv);
        ret = guc_log_control(guc, enable_logging, verbosity);
+       intel_runtime_pm_put(dev_priv);
+       mutex_unlock(&dev_priv->drm.struct_mutex);
+
        if (ret < 0) {
                DRM_DEBUG_DRIVER("guc_logging_control action failed %d\n", ret);
                return ret;
@@ -605,7 +681,11 @@ int i915_guc_log_control(struct drm_i915_private 
*dev_priv, u64 control_val)
                }
 
                /* GuC logging is currently the only user of Guc2Host 
interrupts */
+               mutex_lock(&dev_priv->drm.struct_mutex);
+               intel_runtime_pm_get(dev_priv);
                gen9_enable_guc_interrupts(dev_priv);
+               intel_runtime_pm_put(dev_priv);
+               mutex_unlock(&dev_priv->drm.struct_mutex);
        } else {
                /*
                 * Once logging is disabled, GuC won't generate logs & send an
@@ -627,19 +707,23 @@ void i915_guc_log_register(struct drm_i915_private 
*dev_priv)
        if (!USES_GUC_SUBMISSION(dev_priv) || !i915_modparams.guc_log_level)
                return;
 
-       mutex_lock(&dev_priv->drm.struct_mutex);
        guc_log_late_setup(&dev_priv->guc);
-       mutex_unlock(&dev_priv->drm.struct_mutex);
 }
 
 void i915_guc_log_unregister(struct drm_i915_private *dev_priv)
 {
+       struct intel_guc *guc = &dev_priv->guc;
+
        if (!USES_GUC_SUBMISSION(dev_priv))
                return;
 
        mutex_lock(&dev_priv->drm.struct_mutex);
        /* GuC logging is currently the only user of Guc2Host interrupts */
        gen9_disable_guc_interrupts(dev_priv);
-       guc_log_runtime_destroy(&dev_priv->guc);
+       guc_log_runtime_destroy(guc);
        mutex_unlock(&dev_priv->drm.struct_mutex);
+
+       mutex_lock(&guc->log.runtime.relay_lock);
+       intel_guc_log_relay_destroy(guc);
+       mutex_unlock(&guc->log.runtime.relay_lock);
 }
diff --git a/drivers/gpu/drm/i915/intel_guc_log.h 
b/drivers/gpu/drm/i915/intel_guc_log.h
index f512cf7..378d489 100644
--- a/drivers/gpu/drm/i915/intel_guc_log.h
+++ b/drivers/gpu/drm/i915/intel_guc_log.h
@@ -32,6 +32,13 @@
 struct drm_i915_private;
 struct intel_guc;
 
+/*
+ * The first page is to save log buffer state. Allocate one
+ * extra page for others in case for overlap
+ */
+#define GUC_LOG_SIZE   ((1 + GUC_LOG_DPC_PAGES + 1 + GUC_LOG_ISR_PAGES + \
+                         1 + GUC_LOG_CRASH_PAGES + 1) << PAGE_SHIFT)
+
 struct intel_guc_log {
        u32 flags;
        struct i915_vma *vma;
@@ -41,6 +48,8 @@ struct intel_guc_log {
                struct workqueue_struct *flush_wq;
                struct work_struct flush_work;
                struct rchan *relay_chan;
+               /* To serialize the access to relay_chan */
+               struct mutex relay_lock;
        } runtime;
        /* logging related stats */
        u32 capture_miss_count;
@@ -52,6 +61,8 @@ struct intel_guc_log {
 
 int intel_guc_log_create(struct intel_guc *guc);
 void intel_guc_log_destroy(struct intel_guc *guc);
+int intel_guc_log_relay_create(struct intel_guc *guc);
+void intel_guc_log_relay_destroy(struct intel_guc *guc);
 int i915_guc_log_control(struct drm_i915_private *dev_priv, u64 control_val);
 void i915_guc_log_register(struct drm_i915_private *dev_priv);
 void i915_guc_log_unregister(struct drm_i915_private *dev_priv);
diff --git a/drivers/gpu/drm/i915/intel_uc.c b/drivers/gpu/drm/i915/intel_uc.c
index f78a17b..b119e94 100644
--- a/drivers/gpu/drm/i915/intel_uc.c
+++ b/drivers/gpu/drm/i915/intel_uc.c
@@ -236,28 +236,49 @@ static void guc_disable_communication(struct intel_guc 
*guc)
        guc->send = intel_guc_send_nop;
 }
 
-int intel_uc_init_wq(struct drm_i915_private *dev_priv)
+int intel_uc_init_misc(struct drm_i915_private *dev_priv)
 {
+       struct intel_guc *guc = &dev_priv->guc;
        int ret;
 
        if (!USES_GUC(dev_priv))
                return 0;
 
-       ret = intel_guc_init_wq(&dev_priv->guc);
+       ret = intel_guc_init_wq(guc);
        if (ret) {
                DRM_ERROR("Couldn't allocate workqueues for GuC\n");
-               return ret;
+               goto err;
+       }
+
+       mutex_lock(&guc->log.runtime.relay_lock);
+       ret = intel_guc_log_relay_create(guc);
+       mutex_unlock(&guc->log.runtime.relay_lock);
+
+       if (ret) {
+               DRM_ERROR("Couldn't allocate relay for GuC log\n");
+               goto err_relay;
        }
 
        return 0;
+
+err_relay:
+       intel_guc_fini_wq(guc);
+err:
+       return ret;
 }
 
-void intel_uc_fini_wq(struct drm_i915_private *dev_priv)
+void intel_uc_fini_misc(struct drm_i915_private *dev_priv)
 {
+       struct intel_guc *guc = &dev_priv->guc;
+
        if (!USES_GUC(dev_priv))
                return;
 
-       intel_guc_fini_wq(&dev_priv->guc);
+       intel_guc_fini_wq(guc);
+
+       mutex_lock(&guc->log.runtime.relay_lock);
+       intel_guc_log_relay_destroy(guc);
+       mutex_unlock(&guc->log.runtime.relay_lock);
 }
 
 int intel_uc_init(struct drm_i915_private *dev_priv)
diff --git a/drivers/gpu/drm/i915/intel_uc.h b/drivers/gpu/drm/i915/intel_uc.h
index 8a72497..f2984e0 100644
--- a/drivers/gpu/drm/i915/intel_uc.h
+++ b/drivers/gpu/drm/i915/intel_uc.h
@@ -33,8 +33,8 @@
 void intel_uc_init_mmio(struct drm_i915_private *dev_priv);
 void intel_uc_init_fw(struct drm_i915_private *dev_priv);
 void intel_uc_fini_fw(struct drm_i915_private *dev_priv);
-int intel_uc_init_wq(struct drm_i915_private *dev_priv);
-void intel_uc_fini_wq(struct drm_i915_private *dev_priv);
+int intel_uc_init_misc(struct drm_i915_private *dev_priv);
+void intel_uc_fini_misc(struct drm_i915_private *dev_priv);
 int intel_uc_init_hw(struct drm_i915_private *dev_priv);
 void intel_uc_fini_hw(struct drm_i915_private *dev_priv);
 int intel_uc_init(struct drm_i915_private *dev_priv);
-- 
1.9.1

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