On 24/05/2019 09:45, Chris Wilson wrote:
Apparently VLA structs (e.g. struct { int array[count] }) is a gcc
extension that clang refuses to support as handling memory layout is too
difficult for it. So calculate the size by hand!

v2: Use alloca().

Signed-off-by: Chris Wilson <[email protected]>
Cc: Tvrtko Ursulin <[email protected]>
---
  benchmarks/gem_wsim.c | 115 +++++++++++++++++++++++-------------------
  1 file changed, 64 insertions(+), 51 deletions(-)

diff --git a/benchmarks/gem_wsim.c b/benchmarks/gem_wsim.c
index e2ffb93a9..db19925b1 100644
--- a/benchmarks/gem_wsim.c
+++ b/benchmarks/gem_wsim.c
@@ -1441,6 +1441,29 @@ set_ctx_sseu(struct ctx *ctx, uint64_t slice_mask)
        return slice_mask;
  }
+static size_t sizeof_load_balance(int count)
+{
+       struct i915_context_engines_load_balance *ptr;
+
+       return sizeof(*ptr) + count * sizeof(ptr->engines[0]);
+}
+
+static size_t sizeof_param_engines(int count)
+{
+       struct i915_context_param_engines *ptr;
+
+       return sizeof(*ptr) + count * sizeof(ptr->engines[0]);
+}
+
+static size_t sizeof_engines_bond(int count)
+{
+       struct i915_context_engines_bond *ptr;
+
+       return sizeof(*ptr) + count * sizeof(ptr->engines[0]);
+}
+
+#define alloca0(sz) ({ size_t sz__ = (sz); memset(alloca(sz__), 0, sz__); })
+
  static int
  prepare_workload(unsigned int id, struct workload *wrk, unsigned int flags)
  {
@@ -1676,66 +1699,54 @@ prepare_workload(unsigned int id, struct workload *wrk, 
unsigned int flags)
                }
if (ctx->engine_map) {
-                       I915_DEFINE_CONTEXT_PARAM_ENGINES(set_engines,
-                                                         ctx->engine_map_count 
+ 1);
-                       I915_DEFINE_CONTEXT_ENGINES_LOAD_BALANCE(load_balance,
-                                                                
ctx->engine_map_count);
+                       struct i915_context_param_engines *set_engines =
+                               
alloca0(sizeof_param_engines(ctx->engine_map_count + 1));
+                       struct i915_context_engines_load_balance *load_balance =
+                               
alloca0(sizeof_load_balance(ctx->engine_map_count));
                        struct drm_i915_gem_context_param param = {
                                .ctx_id = ctx_id,
                                .param = I915_CONTEXT_PARAM_ENGINES,
-                               .size = sizeof(set_engines),
-                               .value = to_user_pointer(&set_engines),
+                               .size = 
sizeof_param_engines(ctx->engine_map_count + 1),
+                               .value = to_user_pointer(set_engines),
                        };
+                       struct i915_context_engines_bond *last = NULL;
if (ctx->wants_balance) {
-                               set_engines.extensions =
-                                       to_user_pointer(&load_balance);
+                               set_engines->extensions =
+                                       to_user_pointer(load_balance);
- memset(&load_balance, 0, sizeof(load_balance));
-                               load_balance.base.name =
+                               load_balance->base.name =
                                        I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE;
-                               load_balance.num_siblings =
+                               load_balance->num_siblings =
                                        ctx->engine_map_count;
for (j = 0; j < ctx->engine_map_count; j++)
-                                       load_balance.engines[j] =
+                                       load_balance->engines[j] =
                                                get_engine(ctx->engine_map[j]);
-                       } else {
-                               set_engines.extensions = 0;
                        }
/* Reserve slot for virtual engine. */
-                       set_engines.engines[0].engine_class =
+                       set_engines->engines[0].engine_class =
                                I915_ENGINE_CLASS_INVALID;
-                       set_engines.engines[0].engine_instance =
+                       set_engines->engines[0].engine_instance =
                                I915_ENGINE_CLASS_INVALID_NONE;
for (j = 1; j <= ctx->engine_map_count; j++)
-                               set_engines.engines[j] =
+                               set_engines->engines[j] =
                                        get_engine(ctx->engine_map[j - 1]);
+ last = NULL;
                        for (j = 0; j < ctx->bond_count; j++) {
                                unsigned long mask = ctx->bonds[j].mask;
-                               I915_DEFINE_CONTEXT_ENGINES_BOND(bond,
-                                                                
__builtin_popcount(mask));
-                               struct i915_context_engines_bond *p = NULL, 
*prev;
+                               struct i915_context_engines_bond *bond =
+                                       
alloca0(sizeof_engines_bond(__builtin_popcount(mask)));
                                unsigned int b, e;
- prev = p;
-                               p = alloca(sizeof(bond));
-                               assert(p);
-                               memset(p, 0, sizeof(bond));
+                               bond->base.next_extension = 
to_user_pointer(last);
+                               bond->base.name = I915_CONTEXT_ENGINES_EXT_BOND;
- if (j == 0)
-                                       load_balance.base.next_extension =
-                                               to_user_pointer(p);
-                               else if (j < (ctx->bond_count - 1))
-                                       prev->base.next_extension =
-                                               to_user_pointer(p);
-
-                               p->base.name = I915_CONTEXT_ENGINES_EXT_BOND;
-                               p->virtual_index = 0;
-                               p->master = get_engine(ctx->bonds[j].master);
+                               bond->virtual_index = 0;
+                               bond->master = get_engine(ctx->bonds[j].master);
for (b = 0, e = 0; mask; e++, mask >>= 1) {
                                        unsigned int idx;
@@ -1743,42 +1754,44 @@ prepare_workload(unsigned int id, struct workload *wrk, 
unsigned int flags)
                                        if (!(mask & 1))
                                                continue;
- idx = find_engine(&set_engines.engines[1],
+                                       idx = 
find_engine(&set_engines->engines[1],
                                                          ctx->engine_map_count,
                                                          e);
-                                       p->engines[b++] =
-                                               set_engines.engines[1 + idx];
+                                       bond->engines[b++] =
+                                               set_engines->engines[1 + idx];
                                }
+
+                               last = bond;
                        }
+                       load_balance->base.next_extension = 
to_user_pointer(last);
gem_context_set_param(fd, &param);
                } else if (ctx->wants_balance) {
                        const unsigned int count = num_engines_in_class(VCS);
-                       I915_DEFINE_CONTEXT_ENGINES_LOAD_BALANCE(load_balance,
-                                                                count);
-                       I915_DEFINE_CONTEXT_PARAM_ENGINES(set_engines,
-                                                         count + 1);
+                       struct i915_context_engines_load_balance *load_balance =
+                               alloca0(sizeof_load_balance(count));
+                       struct i915_context_param_engines *set_engines =
+                               alloca0(sizeof_param_engines(count + 1));
                        struct drm_i915_gem_context_param param = {
                                .ctx_id = ctx_id,
                                .param = I915_CONTEXT_PARAM_ENGINES,
-                               .size = sizeof(set_engines),
-                               .value = to_user_pointer(&set_engines),
+                               .size = sizeof_param_engines(count + 1),
+                               .value = to_user_pointer(set_engines),
                        };
- set_engines.extensions = to_user_pointer(&load_balance);
+                       set_engines->extensions = to_user_pointer(load_balance);
- set_engines.engines[0].engine_class =
+                       set_engines->engines[0].engine_class =
                                I915_ENGINE_CLASS_INVALID;
-                       set_engines.engines[0].engine_instance =
+                       set_engines->engines[0].engine_instance =
                                I915_ENGINE_CLASS_INVALID_NONE;
-                       fill_engines_class(&set_engines.engines[1], VCS);
+                       fill_engines_class(&set_engines->engines[1], VCS);
- memset(&load_balance, 0, sizeof(load_balance));
-                       load_balance.base.name =
+                       load_balance->base.name =
                                I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE;
-                       load_balance.num_siblings = count;
+                       load_balance->num_siblings = count;
- fill_engines_class(&load_balance.engines[0], VCS);
+                       fill_engines_class(&load_balance->engines[0], VCS);
gem_context_set_param(fd, &param);
                }


Seems correct.

You couldn't resist throwing in the reverse bond list building simplification as well. :)

Reviewed-by: Tvrtko Ursulin <[email protected]>

Regards,

Tvrtko
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