drm/i915/guc: Pre-allocate output nodes for extraction

In the rare but possible scenario where we are in the midst of
multiple GuC error-capture (and engine reset) events and the
user also triggers a forced full GT reset or the internal watchdog
triggers the same, intel_guc_submission_reset_prepare's call
to flush_work(&guc->ct.requests.worker) can cause the G2H message
handler to trigger intel_guc_capture_store_snapshot upon
receiving new G2H error-capture notifications. This can happen
despite the prior call to disable_submission(guc);. However,
there's no race-free way for intel_guc_capture_store_snapshot to
know that we are in the midst of a reset. That said, we can never
dynamically allocate the output nodes in this handler. Thus, we
shall pre-allocate a fixed number of empty nodes up front (at the
time of ADS registration) that we can consume from or return to
an internal cached list of nodes.

Signed-off-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220321164527.2500062-12-alan.previn.teres.alexis@intel.com

diff --git a/drivers/gpu/drm/i915/gt/uc/guc_capture_fwif.h b/drivers/gpu/drm/i915/gt/uc/guc_capture_fwif.h
index 5d959e6..3624abf 100644 (file)
--- a/drivers/gpu/drm/i915/gt/uc/guc_capture_fwif.h
+++ b/drivers/gpu/drm/i915/gt/uc/guc_capture_fwif.h
@@ -31,7 +31,7 @@ struct __guc_capture_bufstate {
  *
  * A single unit of extracted error-capture output data grouped together
  * at an engine-instance level. We keep these nodes in a linked list.
- * See outlist below.
+ * See cachelist and outlist below.
  */
 struct __guc_capture_parsed_output {
        /*
@@ -190,7 +190,22 @@ struct intel_guc_state_capture {
        void *ads_null_cache;
 
        /**
-        * @outlist: allocated nodes with parsed engine-instance error capture data
+        * @cachelist: Pool of pre-allocated nodes for error capture output
+        *
+        * We need this pool of pre-allocated nodes because we cannot
+        * dynamically allocate new nodes when receiving the G2H notification
+        * because the event handlers for all G2H event-processing is called
+        * by the ct processing worker queue and when that queue is being
+        * processed, there is no absoluate guarantee that we are not in the
+        * midst of a GT reset operation (which doesn't allow allocations).
+        */
+       struct list_head cachelist;
+#define PREALLOC_NODES_MAX_COUNT (3 * GUC_MAX_ENGINE_CLASSES * GUC_MAX_INSTANCES_PER_CLASS)
+#define PREALLOC_NODES_DEFAULT_NUMREGS 64
+       int max_mmio_per_node;
+
+       /**
+        * @outlist: Pool of pre-allocated nodes for error capture output
         *
         * A linked list of parsed GuC error-capture output data before
         * reporting with formatting via i915_gpu_coredump. Each node in this linked list shall

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_capture.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_capture.c
index 25a5f10..6af86c2 100644 (file)
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_capture.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_capture.c
@@ -581,6 +581,8 @@ intel_guc_capture_getlistsize(struct intel_guc *guc, u32 owner, u32 type, u32 cl
        return 0;
 }
 
+static void guc_capture_create_prealloc_nodes(struct intel_guc *guc);
+
 int
 intel_guc_capture_getlist(struct intel_guc *guc, u32 owner, u32 type, u32 classid,
                          void **outptr)
@@ -601,6 +603,12 @@ intel_guc_capture_getlist(struct intel_guc *guc, u32 owner, u32 type, u32 classi
                return cache->status;
        }
 
+       /*
+        * ADS population of input registers is a good
+        * time to pre-allocate cachelist output nodes
+        */
+       guc_capture_create_prealloc_nodes(guc);
+
        ret = intel_guc_capture_getlistsize(guc, owner, type, classid, &size);
        if (ret) {
                cache->is_valid = true;
@@ -742,7 +750,8 @@ intel_guc_capture_output_min_size_est(struct intel_guc *guc)
  *                                err-state-captured register-list we find, we alloc 'C':
  *      --> alloc C: A capture-output-node structure that includes misc capture info along
  *                   with 3 register list dumps (global, engine-class and engine-instance)
- *                   This node is dynamically allocated and populated with the error-capture
+ *                   This node is created from a pre-allocated list of blank nodes in
+ *                   guc->capture->cachelist and populated with the error-capture
  *                   data from GuC and then it's added into guc->capture->outlist linked
  *                   list. This list is used for matchup and printout by i915_gpu_coredump
  *                   and err_print_gt, (when user invokes the error capture sysfs).
@@ -902,19 +911,20 @@ guc_capture_delete_one_node(struct intel_guc *guc, struct __guc_capture_parsed_o
 }
 
 static void
-guc_capture_delete_nodes(struct intel_guc *guc)
+guc_capture_delete_prealloc_nodes(struct intel_guc *guc)
 {
+       struct __guc_capture_parsed_output *n, *ntmp;
+
        /*
         * NOTE: At the end of driver operation, we must assume that we
-        * have nodes in outlist from unclaimed error capture events
-        * that occurred prior to shutdown.
+        * have prealloc nodes in both the cachelist as well as outlist
+        * if unclaimed error capture events occurred prior to shutdown.
         */
-       if (!list_empty(&guc->capture->outlist)) {
-               struct __guc_capture_parsed_output *n, *ntmp;
+       list_for_each_entry_safe(n, ntmp, &guc->capture->outlist, link)
+               guc_capture_delete_one_node(guc, n);
 
-               list_for_each_entry_safe(n, ntmp, &guc->capture->outlist, link)
-                       guc_capture_delete_one_node(guc, n);
-       }
+       list_for_each_entry_safe(n, ntmp, &guc->capture->cachelist, link)
+               guc_capture_delete_one_node(guc, n);
 }
 
 static void
@@ -932,20 +942,79 @@ guc_capture_add_node_to_outlist(struct intel_guc_state_capture *gc,
 }
 
 static void
+guc_capture_add_node_to_cachelist(struct intel_guc_state_capture *gc,
+                                 struct __guc_capture_parsed_output *node)
+{
+       guc_capture_add_node_to_list(node, &gc->cachelist);
+}
+
+static void
 guc_capture_init_node(struct intel_guc *guc, struct __guc_capture_parsed_output *node)
 {
+       struct guc_mmio_reg *tmp[GUC_CAPTURE_LIST_TYPE_MAX];
+       int i;
+
+       for (i = 0; i < GUC_CAPTURE_LIST_TYPE_MAX; ++i) {
+               tmp[i] = node->reginfo[i].regs;
+               memset(tmp[i], 0, sizeof(struct guc_mmio_reg) *
+                      guc->capture->max_mmio_per_node);
+       }
+       memset(node, 0, sizeof(*node));
+       for (i = 0; i < GUC_CAPTURE_LIST_TYPE_MAX; ++i)
+               node->reginfo[i].regs = tmp[i];
+
        INIT_LIST_HEAD(&node->link);
 }
 
 static struct __guc_capture_parsed_output *
+guc_capture_get_prealloc_node(struct intel_guc *guc)
+{
+       struct __guc_capture_parsed_output *found = NULL;
+
+       if (!list_empty(&guc->capture->cachelist)) {
+               struct __guc_capture_parsed_output *n, *ntmp;
+
+               /* get first avail node from the cache list */
+               list_for_each_entry_safe(n, ntmp, &guc->capture->cachelist, link) {
+                       found = n;
+                       list_del(&n->link);
+                       break;
+               }
+       } else {
+               struct __guc_capture_parsed_output *n, *ntmp;
+
+               /* traverse down and steal back the oldest node already allocated */
+               list_for_each_entry_safe(n, ntmp, &guc->capture->outlist, link) {
+                       found = n;
+               }
+               if (found)
+                       list_del(&found->link);
+       }
+       if (found)
+               guc_capture_init_node(guc, found);
+
+       return found;
+}
+
+static struct __guc_capture_parsed_output *
 guc_capture_alloc_one_node(struct intel_guc *guc)
 {
        struct __guc_capture_parsed_output *new;
+       int i;
 
        new = kzalloc(sizeof(*new), GFP_KERNEL);
        if (!new)
                return NULL;
 
+       for (i = 0; i < GUC_CAPTURE_LIST_TYPE_MAX; ++i) {
+               new->reginfo[i].regs = kcalloc(guc->capture->max_mmio_per_node,
+                                              sizeof(struct guc_mmio_reg), GFP_KERNEL);
+               if (!new->reginfo[i].regs) {
+                       while (i)
+                               kfree(new->reginfo[--i].regs);
+                       return NULL;
+               }
+       }
        guc_capture_init_node(guc, new);
 
        return new;
@@ -958,7 +1027,7 @@ guc_capture_clone_node(struct intel_guc *guc, struct __guc_capture_parsed_output
        struct __guc_capture_parsed_output *new;
        int i;
 
-       new = guc_capture_alloc_one_node(guc);
+       new = guc_capture_get_prealloc_node(guc);
        if (!new)
                return NULL;
        if (!original)
@@ -969,13 +1038,12 @@ guc_capture_clone_node(struct intel_guc *guc, struct __guc_capture_parsed_output
        /* copy reg-lists that we want to clone */
        for (i = 0; i < GUC_CAPTURE_LIST_TYPE_MAX; ++i) {
                if (keep_reglist_mask & BIT(i)) {
-                       new->reginfo[i].regs = kcalloc(original->reginfo[i].num_regs,
-                                                      sizeof(struct guc_mmio_reg), GFP_KERNEL);
-                       if (!new->reginfo[i].regs)
-                               goto bail_clone;
+                       GEM_BUG_ON(original->reginfo[i].num_regs  >
+                                  guc->capture->max_mmio_per_node);
 
                        memcpy(new->reginfo[i].regs, original->reginfo[i].regs,
                               original->reginfo[i].num_regs * sizeof(struct guc_mmio_reg));
+
                        new->reginfo[i].num_regs = original->reginfo[i].num_regs;
                        new->reginfo[i].vfid  = original->reginfo[i].vfid;
 
@@ -990,12 +1058,58 @@ guc_capture_clone_node(struct intel_guc *guc, struct __guc_capture_parsed_output
        }
 
        return new;
+}
 
-bail_clone:
-       for (i = 0; i < GUC_CAPTURE_LIST_TYPE_MAX; ++i)
-               kfree(new->reginfo[i].regs);
-       kfree(new);
-       return NULL;
+static void
+__guc_capture_create_prealloc_nodes(struct intel_guc *guc)
+{
+       struct __guc_capture_parsed_output *node = NULL;
+       struct drm_i915_private *i915 = guc_to_gt(guc)->i915;
+       int i;
+
+       for (i = 0; i < PREALLOC_NODES_MAX_COUNT; ++i) {
+               node = guc_capture_alloc_one_node(guc);
+               if (!node) {
+                       drm_warn(&i915->drm, "GuC Capture pre-alloc-cache failure\n");
+                       /* dont free the priors, use what we got and cleanup at shutdown */
+                       return;
+               }
+               guc_capture_add_node_to_cachelist(guc->capture, node);
+       }
+}
+
+static int
+guc_get_max_reglist_count(struct intel_guc *guc)
+{
+       int i, j, k, tmp, maxregcount = 0;
+
+       for (i = 0; i < GUC_CAPTURE_LIST_INDEX_MAX; ++i) {
+               for (j = 0; j < GUC_CAPTURE_LIST_TYPE_MAX; ++j) {
+                       for (k = 0; k < GUC_MAX_ENGINE_CLASSES; ++k) {
+                               if (j == GUC_CAPTURE_LIST_TYPE_GLOBAL && k > 0)
+                                       continue;
+
+                               tmp = guc_cap_list_num_regs(guc->capture, i, j, k);
+                               if (tmp > maxregcount)
+                                       maxregcount = tmp;
+                       }
+               }
+       }
+       if (!maxregcount)
+               maxregcount = PREALLOC_NODES_DEFAULT_NUMREGS;
+
+       return maxregcount;
+}
+
+static void
+guc_capture_create_prealloc_nodes(struct intel_guc *guc)
+{
+       /* skip if we've already done the pre-alloc */
+       if (guc->capture->max_mmio_per_node)
+               return;
+
+       guc->capture->max_mmio_per_node = guc_get_max_reglist_count(guc);
+       __guc_capture_create_prealloc_nodes(guc);
 }
 
 static int
@@ -1111,13 +1225,13 @@ guc_capture_extract_reglists(struct intel_guc *guc, struct __guc_capture_bufstat
                                guc_capture_add_node_to_outlist(guc->capture, node);
                                node = NULL;
                        } else if (datatype == GUC_CAPTURE_LIST_TYPE_ENGINE_CLASS &&
-                                  node->reginfo[GUC_CAPTURE_LIST_TYPE_ENGINE_CLASS].regs) {
+                                  node->reginfo[GUC_CAPTURE_LIST_TYPE_ENGINE_CLASS].num_regs) {
                                /* Add to list, clone node and duplicate global list */
                                guc_capture_add_node_to_outlist(guc->capture, node);
                                node = guc_capture_clone_node(guc, node,
                                                              GCAP_PARSED_REGLIST_INDEX_GLOBAL);
                        } else if (datatype == GUC_CAPTURE_LIST_TYPE_ENGINE_INSTANCE &&
-                                  node->reginfo[GUC_CAPTURE_LIST_TYPE_ENGINE_INSTANCE].regs) {
+                                  node->reginfo[GUC_CAPTURE_LIST_TYPE_ENGINE_INSTANCE].num_regs) {
                                /* Add to list, clone node and duplicate global + class lists */
                                guc_capture_add_node_to_outlist(guc->capture, node);
                                node = guc_capture_clone_node(guc, node,
@@ -1127,7 +1241,7 @@ guc_capture_extract_reglists(struct intel_guc *guc, struct __guc_capture_bufstat
                }
 
                if (!node) {
-                       node = guc_capture_alloc_one_node(guc);
+                       node = guc_capture_get_prealloc_node(guc);
                        if (!node) {
                                ret = -ENOMEM;
                                break;
@@ -1152,17 +1266,13 @@ guc_capture_extract_reglists(struct intel_guc *guc, struct __guc_capture_bufstat
                        break;
                }
 
-               regs = NULL;
                numregs = FIELD_GET(CAP_HDR_NUM_MMIOS, hdr.num_mmios);
-               if (numregs) {
-                       regs = kcalloc(numregs, sizeof(struct guc_mmio_reg), GFP_KERNEL);
-                       if (!regs) {
-                               ret = -ENOMEM;
-                               break;
-                       }
+               if (numregs > guc->capture->max_mmio_per_node) {
+                       drm_dbg(&i915->drm, "GuC Capture list extraction clipped by prealloc!\n");
+                       numregs = guc->capture->max_mmio_per_node;
                }
                node->reginfo[datatype].num_regs = numregs;
-               node->reginfo[datatype].regs = regs;
+               regs = node->reginfo[datatype].regs;
                i = 0;
                while (numregs--) {
                        if (guc_capture_log_get_register(guc, buf, &regs[i++])) {
@@ -1182,8 +1292,8 @@ bailout:
                                break;
                        }
                }
-               /* else free it */
-               kfree(node);
+               if (node) /* else return it back to cache list */
+                       guc_capture_add_node_to_cachelist(guc->capture, node);
        }
        return ret;
 }
@@ -1291,7 +1401,7 @@ void intel_guc_capture_destroy(struct intel_guc *guc)
 
        guc_capture_free_ads_cache(guc->capture);
 
-       guc_capture_delete_nodes(guc);
+       guc_capture_delete_prealloc_nodes(guc);
 
        guc_capture_free_extlists(guc->capture->extlists);
        kfree(guc->capture->extlists);
@@ -1309,6 +1419,7 @@ int intel_guc_capture_init(struct intel_guc *guc)
        guc->capture->reglists = guc_capture_get_device_reglist(guc);
 
        INIT_LIST_HEAD(&guc->capture->outlist);
+       INIT_LIST_HEAD(&guc->capture->cachelist);
 
        return 0;
 }