Re: [PATCH] drm/amdgpu: Fix multiple GPU resets in XGMI hive.

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Am 10.05.22 um 20:53 schrieb Andrey Grodzovsky:

On 2022-05-10 13:19, Christian König wrote:
Am 10.05.22 um 19:01 schrieb Andrey Grodzovsky:

On 2022-05-10 12:17, Christian König wrote:
Am 10.05.22 um 18:00 schrieb Andrey Grodzovsky:
[SNIP]
That's one of the reasons why we should have multiple work items for job based reset and other reset sources.

See the whole idea is the following:
1. We have one single queued work queue for each reset domain which makes sure that all reset requests execute in order. 2. We have one delayed work item for each scheduler which fires when a timeout on a scheduler occurs and eventually calls the reset procedure with the last running job.
3. We have one work item for each necessary hard reset.

The delayed work item from the scheduler first tries a soft recovery and checks if a hard reset is really necessary. If it's not necessary and we can cancel the offending job we skip the hard reset.

The hard reset work item doesn't do any of those checks and just does a reset no matter what.

When we really do a reset, independent if its triggered by a job or other source we cancel all sources at the end of the reset procedure.

This makes sure that a) We only do one reset even when multiple sources fire at the same time and b) when any source bails out and only does a soft recovery we do a full reset anyway when necessary.

That design was outlined multiple times now on the mailing list and looks totally clear to me. We should probably document that somewhere.


If you look at the patch what you described above is exactly what is happening - since scheduler's delayed work is different from any non scheduler delayed work the SW reset which might take place from scheduler's reset will not have any impact on any non scheduler delayed work and will not cancel them. In case the scheduler actually reaches the point of HW reset it will cancel out all pending reset works from any other sources on the same reset domain. Non scheduler reset will always proceed to do full HW reset and will cancel any other pending resets.

Ok, but why you then need that linked list? The number of reset sources should be static and not in any way dynamic.


So array reset_src[i] holds a pointer to pending delayed work from source i or NULL if no pedning work ? What if same source triggers multiple reset requests such as multiple RAS errors at once , don't set the delayed work pointer in the arr[RAS_index] if it's already not NULL ?


See using the linked list sounds like you only wanted to cancel the reset sources raised so far which would not be correct as far as I can see.


Not clear about this one ? We do want to cancel those reset sources that were raised so far because we just did a HW reset which should fix them anyway ? Those who not raised reset request so far their respective array index will have a NULL ptr.

And exactly that's what I want to prevent. See you don't care if a reset source has fired once, twice, ten times or never. You just cancel all of them!

That's why I want to come to a static list of reset sources.

E.g. in the reset code (either before or after the reset, that's debatable) you do something like this:

for (i = 0; i < num_ring; ++i)
    cancel_delayed_work(ring[i]->scheduler....)
cancel_work(adev->ras_work);
cancel_work(adev->iofault_work);
cancel_work(adev->debugfs_work);
...

You don't really need to track which reset source has fired and which hasn't, because that would be racy again. Instead just bluntly reset all possible sources.

Christian.


I don't say we care if it fired once or twice (I need to add a fix to only insert reset work to pending reset list if it's not already there), the point of using list (or array) to which you add and from which you remove is that the logic of this is encapsulated within reset domain. In your way we need to be aware who exactly schedules reset work and explicitly cancel them, this also means that for any new source added in the future you will need to remember to add him

I don't think that this is a valid argument. Additionally to the schedulers we probably just need less than a handful of reset sources, most likely even just one or two is enough.

The only justification I can see of having additional separate reset sources would be if somebody wants to know if a specific source has been handled or not (e.g. call flush_work() or work_pending()). Like in the case of a reset triggered through debugfs.

to the cancellation list which you showed above. In current way all this done automatically within reset_domain code and it's agnostic to specific driver and it's specific list of reset sources. Also in case we would want to generalize reset_domain to other GPU drivers (which was a plan as far as i remember) this explicit mention of each reset works for cancellation is again less suitable in my opinion.

Well we could put the work item for the scheduler independent reset source into the reset domain as well. But I'm not sure those additional reset sources should be part of any common handling, that is largely amdgpu specific.

Christian.


Andrey




Andrey




The only difference is I chose to do the canceling right BEFORE the HW reset and not AFTER. I did this because I see a possible race where a new reset request is being generated exactly after we finished the HW reset but before we canceled out all pending resets - in such case you wold not want to cancel this 'border line new' reset request.

Why not? Any new reset request directly after a hardware reset is most likely just falsely generated by the reset itself.

Ideally I would cancel all sources after the reset, but before starting any new work.

Regards,
Christian.



Andrey



Regards,
Christian.

You can see that if many different reset sources share same work struct what can happen is that the first to obtain the lock you describe bellow might opt out from full HW reset because his bad job did signal for example or because his hunged IP block was able to recover through SW reset but in the meantime another reset source who needed an actual HW reset just silently returned and we end up with unhandled reset request. True that today this happens only to job timeout reset sources that are handled form within the scheduler and won't use this single work struct but no one prevents a future case for this to happen and also, if we actually want to unify scheduler time out handlers within reset domain (which seems to me the right design approach) we won't be able to use just one work struct for this reason anyway.


Just to add to this point - a reset domain is co-operative domain. In addition to sharing a set of clients from various reset sources for one device, it also will have a set of devices like in XGMI hive. The job timeout on one device may not eventually result in result, but a RAS error happening on another device at the same time would need a reset. The second device's RAS error cannot return seeing  that a reset work already started, or ignore the reset work given that another device has filled the reset data.

When there is a reset domain, it should take care of the work scheduled and keeping it in device or any other level doesn't sound good.

Thanks,
Lijo

Andrey



I'd put the reset work struct into the reset_domain struct. That way you'd have exactly one worker for the reset domain. You could implement a lock-less scheme to decide whether you need to schedule a reset, e.g. using an atomic counter in the shared work struct that gets incremented when a client wants to trigger a reset (atomic_add_return). If that counter is exactly 1 after incrementing, you need to fill in the rest of the work struct and schedule the work. Otherwise, it's already scheduled (or another client is in the process of scheduling it) and you just return. When the worker finishes (after confirming a successful reset), it resets the counter to 0, so the next client requesting a reset will schedule the worker again.

Regards,
  Felix






Additional to that keep in mind that you can't allocate any memory before or during the GPU reset nor wait for the reset to complete (so you can't allocate anything on the stack either).


There is no dynamic allocation here, regarding stack allocations - we do it all the time when we call functions, even during GPU resets, how on stack allocation of work struct in amdgpu_device_gpu_recover is different from any other local variable we allocate in any function we call ?

I am also not sure why it's not allowed to wait for reset to complete ? Also, see in amdgpu_ras_do_recovery and gpu_recover_get (debugfs) - the caller expects the reset to complete before he returns. I can probably work around it in RAS code by calling atomic_set(&ras->in_recovery, 0) from some callback within actual reset function but regarding sysfs it actually expects a result returned indicating whether the call was successful or not.

Andrey



I don't think that concept you try here will work.

Regards,
Christian.

Also in general seems to me it's cleaner approach where this logic (the work items) are held and handled in reset_domain and are not split in each adev or any other entity. We might want in the future to even move the scheduler handling into reset domain since reset domain is supposed to be a generic things and not only or AMD.

Andrey




Andrey



Regards,
Christian.


Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
Tested-by: Bai Zoy <Zoy.Bai@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu.h | 11 +---
drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 17 +++--
drivers/gpu/drm/amd/amdgpu/amdgpu_reset.c | 3 +
drivers/gpu/drm/amd/amdgpu/amdgpu_reset.h | 73 +++++++++++++++++++++-
drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h | 3 +-
drivers/gpu/drm/amd/amdgpu/mxgpu_ai.c | 7 ++-
drivers/gpu/drm/amd/amdgpu/mxgpu_nv.c | 7 ++-
drivers/gpu/drm/amd/amdgpu/mxgpu_vi.c | 7 ++-
  8 files changed, 104 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 4264abc5604d..99efd8317547 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -109,6 +109,7 @@
  #include "amdgpu_fdinfo.h"
  #include "amdgpu_mca.h"
  #include "amdgpu_ras.h"
+#include "amdgpu_reset.h"
    #define MAX_GPU_INSTANCE 16
  @@ -509,16 +510,6 @@ struct amdgpu_allowed_register_entry {
      bool grbm_indexed;
  };
  -enum amd_reset_method {
-    AMD_RESET_METHOD_NONE = -1,
-    AMD_RESET_METHOD_LEGACY = 0,
-    AMD_RESET_METHOD_MODE0,
-    AMD_RESET_METHOD_MODE1,
-    AMD_RESET_METHOD_MODE2,
-    AMD_RESET_METHOD_BACO,
-    AMD_RESET_METHOD_PCI,
-};
-
  struct amdgpu_video_codec_info {
      u32 codec_type;
      u32 max_width;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index e582f1044c0f..7fa82269c30f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -5201,6 +5201,12 @@ int amdgpu_device_gpu_recover_imp(struct amdgpu_device *adev,
      }
        tmp_vram_lost_counter = atomic_read(&((adev)->vram_lost_counter));
+
+    /* Drop all pending resets since we will reset now anyway */ +    tmp_adev = list_first_entry(device_list_handle, struct amdgpu_device,
+ reset_list);
+ amdgpu_reset_pending_list(tmp_adev->reset_domain);
+
      /* Actual ASIC resets if needed.*/
      /* Host driver will handle XGMI hive reset for SRIOV */
      if (amdgpu_sriov_vf(adev)) {
@@ -5296,7 +5302,7 @@ int amdgpu_device_gpu_recover_imp(struct amdgpu_device *adev,
  }
    struct amdgpu_recover_work_struct {
-    struct work_struct base;
+    struct amdgpu_reset_work_struct base;
      struct amdgpu_device *adev;
      struct amdgpu_job *job;
      int ret;
@@ -5304,7 +5310,7 @@ struct amdgpu_recover_work_struct {
    static void amdgpu_device_queue_gpu_recover_work(struct work_struct *work)
  {
-    struct amdgpu_recover_work_struct *recover_work = container_of(work, struct amdgpu_recover_work_struct, base); +    struct amdgpu_recover_work_struct *recover_work = container_of(work, struct amdgpu_recover_work_struct, base.base.work);         recover_work->ret = amdgpu_device_gpu_recover_imp(recover_work->adev, recover_work->job);
  }
@@ -5316,12 +5322,15 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
  {
      struct amdgpu_recover_work_struct work = {.adev = adev, .job = job};   -    INIT_WORK(&work.base, amdgpu_device_queue_gpu_recover_work); + INIT_DELAYED_WORK(&work.base.base, amdgpu_device_queue_gpu_recover_work);
+ INIT_LIST_HEAD(&work.base.node);
        if (!amdgpu_reset_domain_schedule(adev->reset_domain, &work.base))
          return -EAGAIN;
  -    flush_work(&work.base);
+ flush_delayed_work(&work.base.base);
+
+ amdgpu_reset_domain_del_pendning_work(adev->reset_domain, &work.base);
        return work.ret;
  }
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_reset.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_reset.c
index c80af0889773..ffddd419c351 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_reset.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_reset.c
@@ -134,6 +134,9 @@ struct amdgpu_reset_domain *amdgpu_reset_create_reset_domain(enum amdgpu_reset_d
atomic_set(&reset_domain->in_gpu_reset, 0);
init_rwsem(&reset_domain->sem);
  + INIT_LIST_HEAD(&reset_domain->pending_works);
+ mutex_init(&reset_domain->reset_lock);
+
      return reset_domain;
  }
  diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_reset.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_reset.h
index 1949dbe28a86..863ec5720fc1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_reset.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_reset.h
@@ -24,7 +24,18 @@
  #ifndef __AMDGPU_RESET_H__
  #define __AMDGPU_RESET_H__
  -#include "amdgpu.h"
+
+#include <linux/atomic.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/kref.h>
+#include <linux/rwsem.h>
+#include <linux/workqueue.h>
+
+struct amdgpu_device;
+struct amdgpu_job;
+struct amdgpu_hive_info;
+
    enum AMDGPU_RESET_FLAGS {
  @@ -32,6 +43,17 @@ enum AMDGPU_RESET_FLAGS {
      AMDGPU_SKIP_HW_RESET = 1,
  };
  +
+enum amd_reset_method {
+    AMD_RESET_METHOD_NONE = -1,
+    AMD_RESET_METHOD_LEGACY = 0,
+    AMD_RESET_METHOD_MODE0,
+    AMD_RESET_METHOD_MODE1,
+    AMD_RESET_METHOD_MODE2,
+    AMD_RESET_METHOD_BACO,
+    AMD_RESET_METHOD_PCI,
+};
+
  struct amdgpu_reset_context {
      enum amd_reset_method method;
      struct amdgpu_device *reset_req_dev;
@@ -40,6 +62,8 @@ struct amdgpu_reset_context {
      unsigned long flags;
  };
  +struct amdgpu_reset_control;
+
  struct amdgpu_reset_handler {
      enum amd_reset_method reset_method;
      struct list_head handler_list;
@@ -76,12 +100,21 @@ enum amdgpu_reset_domain_type {
      XGMI_HIVE
  };
  +
+struct amdgpu_reset_work_struct {
+    struct delayed_work base;
+    struct list_head node;
+};
+
  struct amdgpu_reset_domain {
      struct kref refcount;
      struct workqueue_struct *wq;
      enum amdgpu_reset_domain_type type;
      struct rw_semaphore sem;
      atomic_t in_gpu_reset;
+
+    struct list_head pending_works;
+    struct mutex reset_lock;
  };
    @@ -113,9 +146,43 @@ static inline void amdgpu_reset_put_reset_domain(struct amdgpu_reset_domain *dom
  }
    static inline bool amdgpu_reset_domain_schedule(struct amdgpu_reset_domain *domain,
-                        struct work_struct *work)
+                        struct amdgpu_reset_work_struct *work)
  {
-    return queue_work(domain->wq, work);
+ mutex_lock(&domain->reset_lock);
+
+    if (!queue_delayed_work(domain->wq, &work->base, 0)) {
+ mutex_unlock(&domain->reset_lock);
+        return false;
+    }
+
+ list_add_tail(&work->node, &domain->pending_works);
+ mutex_unlock(&domain->reset_lock);
+
+    return true;
+}
+
+static inline void amdgpu_reset_domain_del_pendning_work(struct amdgpu_reset_domain *domain,
+                  struct amdgpu_reset_work_struct *work)
+{
+ mutex_lock(&domain->reset_lock);
+ list_del_init(&work->node);
+ mutex_unlock(&domain->reset_lock);
+}
+
+static inline void amdgpu_reset_pending_list(struct amdgpu_reset_domain *domain)
+{
+    struct amdgpu_reset_work_struct *entry, *tmp;
+
+ mutex_lock(&domain->reset_lock);
+    list_for_each_entry_safe(entry, tmp, &domain->pending_works, node) {
+
+ list_del_init(&entry->node);
+
+        /* Stop any other related pending resets */
+ cancel_delayed_work(&entry->base);
+    }
+
+ mutex_unlock(&domain->reset_lock);
  }
    void amdgpu_device_lock_reset_domain(struct amdgpu_reset_domain *reset_domain); diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h
index 239f232f9c02..574e870d3064 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h
@@ -25,6 +25,7 @@
  #define AMDGPU_VIRT_H
    #include "amdgv_sriovmsg.h"
+#include "amdgpu_reset.h"
    #define AMDGPU_SRIOV_CAPS_SRIOV_VBIOS (1 << 0) /* vBIOS is sr-iov ready */   #define AMDGPU_SRIOV_CAPS_ENABLE_IOV (1 << 1) /* sr-iov is enabled on this GPU */
@@ -230,7 +231,7 @@ struct amdgpu_virt {
      uint32_t reg_val_offs;
      struct amdgpu_irq_src ack_irq;
      struct amdgpu_irq_src rcv_irq;
-    struct work_struct flr_work;
+    struct amdgpu_reset_work_struct flr_work;
      struct amdgpu_mm_table mm_table;
      const struct amdgpu_virt_ops *ops;
      struct amdgpu_vf_error_buffer vf_errors;
diff --git a/drivers/gpu/drm/amd/amdgpu/mxgpu_ai.c b/drivers/gpu/drm/amd/amdgpu/mxgpu_ai.c
index b81acf59870c..f3d1c2be9292 100644
--- a/drivers/gpu/drm/amd/amdgpu/mxgpu_ai.c
+++ b/drivers/gpu/drm/amd/amdgpu/mxgpu_ai.c
@@ -251,7 +251,7 @@ static int xgpu_ai_set_mailbox_ack_irq(struct amdgpu_device *adev,     static void xgpu_ai_mailbox_flr_work(struct work_struct *work)
  {
-    struct amdgpu_virt *virt = container_of(work, struct amdgpu_virt, flr_work); +    struct amdgpu_virt *virt = container_of(work, struct amdgpu_virt, flr_work.base.work);       struct amdgpu_device *adev = container_of(virt, struct amdgpu_device, virt);
      int timeout = AI_MAILBOX_POLL_FLR_TIMEDOUT;
  @@ -380,7 +380,8 @@ int xgpu_ai_mailbox_get_irq(struct amdgpu_device *adev)
          return r;
      }
  - INIT_WORK(&adev->virt.flr_work, xgpu_ai_mailbox_flr_work); + INIT_DELAYED_WORK(&adev->virt.flr_work.base, xgpu_ai_mailbox_flr_work);
+ INIT_LIST_HEAD(&adev->virt.flr_work.node);
        return 0;
  }
@@ -389,6 +390,8 @@ void xgpu_ai_mailbox_put_irq(struct amdgpu_device *adev)
  {
      amdgpu_irq_put(adev, &adev->virt.ack_irq, 0);
      amdgpu_irq_put(adev, &adev->virt.rcv_irq, 0);
+
+ amdgpu_reset_domain_del_pendning_work(adev->reset_domain, &adev->virt.flr_work);
  }
    static int xgpu_ai_request_init_data(struct amdgpu_device *adev) diff --git a/drivers/gpu/drm/amd/amdgpu/mxgpu_nv.c b/drivers/gpu/drm/amd/amdgpu/mxgpu_nv.c
index 22c10b97ea81..927b3d5bb1d0 100644
--- a/drivers/gpu/drm/amd/amdgpu/mxgpu_nv.c
+++ b/drivers/gpu/drm/amd/amdgpu/mxgpu_nv.c
@@ -275,7 +275,7 @@ static int xgpu_nv_set_mailbox_ack_irq(struct amdgpu_device *adev,     static void xgpu_nv_mailbox_flr_work(struct work_struct *work)
  {
-    struct amdgpu_virt *virt = container_of(work, struct amdgpu_virt, flr_work); +    struct amdgpu_virt *virt = container_of(work, struct amdgpu_virt, flr_work.base.work);       struct amdgpu_device *adev = container_of(virt, struct amdgpu_device, virt);
      int timeout = NV_MAILBOX_POLL_FLR_TIMEDOUT;
  @@ -407,7 +407,8 @@ int xgpu_nv_mailbox_get_irq(struct amdgpu_device *adev)
          return r;
      }
  - INIT_WORK(&adev->virt.flr_work, xgpu_nv_mailbox_flr_work); + INIT_DELAYED_WORK(&adev->virt.flr_work.base, xgpu_nv_mailbox_flr_work);
+ INIT_LIST_HEAD(&adev->virt.flr_work.node);
        return 0;
  }
@@ -416,6 +417,8 @@ void xgpu_nv_mailbox_put_irq(struct amdgpu_device *adev)
  {
      amdgpu_irq_put(adev, &adev->virt.ack_irq, 0);
      amdgpu_irq_put(adev, &adev->virt.rcv_irq, 0);
+
+ amdgpu_reset_domain_del_pendning_work(adev->reset_domain, &adev->virt.flr_work);
  }
    const struct amdgpu_virt_ops xgpu_nv_virt_ops = {
diff --git a/drivers/gpu/drm/amd/amdgpu/mxgpu_vi.c b/drivers/gpu/drm/amd/amdgpu/mxgpu_vi.c
index 7b63d30b9b79..1d4ef5c70730 100644
--- a/drivers/gpu/drm/amd/amdgpu/mxgpu_vi.c
+++ b/drivers/gpu/drm/amd/amdgpu/mxgpu_vi.c
@@ -512,7 +512,7 @@ static int xgpu_vi_set_mailbox_ack_irq(struct amdgpu_device *adev,     static void xgpu_vi_mailbox_flr_work(struct work_struct *work)
  {
-    struct amdgpu_virt *virt = container_of(work, struct amdgpu_virt, flr_work); +    struct amdgpu_virt *virt = container_of(work, struct amdgpu_virt, flr_work.base.work);       struct amdgpu_device *adev = container_of(virt, struct amdgpu_device, virt);
        /* wait until RCV_MSG become 3 */
@@ -610,7 +610,8 @@ int xgpu_vi_mailbox_get_irq(struct amdgpu_device *adev)
          return r;
      }
  - INIT_WORK(&adev->virt.flr_work, xgpu_vi_mailbox_flr_work); + INIT_DELAYED_WORK(&adev->virt.flr_work.base, xgpu_vi_mailbox_flr_work);
+ INIT_LIST_HEAD(&adev->virt.flr_work.node);
        return 0;
  }
@@ -619,6 +620,8 @@ void xgpu_vi_mailbox_put_irq(struct amdgpu_device *adev)
  {
      amdgpu_irq_put(adev, &adev->virt.ack_irq, 0);
      amdgpu_irq_put(adev, &adev->virt.rcv_irq, 0);
+
+ amdgpu_reset_domain_del_pendning_work(adev->reset_domain, &adev->virt.flr_work);
  }
    const struct amdgpu_virt_ops xgpu_vi_virt_ops = {










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