Re: [PATCH 6/7] drm/exec: Pass in initial # of objects

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Am 30.10.23 um 14:38 schrieb Rob Clark:

On Mon, Oct 30, 2023 at 1:05 AM Christian König
<christian.koenig@xxxxxxx> wrote:

Am 27.10.23 um 18:58 schrieb Rob Clark:

From: Rob Clark <robdclark@xxxxxxxxxxxx>

In cases where the # is known ahead of time, it is silly to do the table
resize dance.

Ah, yes that was my initial implementation as well, but I ditched that
because nobody actually used it.

One comment below.


Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
---
   drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c  |  2 +-
   drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c |  4 ++--
   drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c |  4 ++--
   drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c |  4 ++--
   drivers/gpu/drm/drm_exec.c              | 15 ++++++++++++---
   drivers/gpu/drm/nouveau/nouveau_exec.c  |  2 +-
   drivers/gpu/drm/nouveau/nouveau_uvmm.c  |  2 +-
   include/drm/drm_exec.h                  |  2 +-
   8 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index efdb1c48f431..d27ca8f61929 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -65,7 +65,7 @@ static int amdgpu_cs_parser_init(struct amdgpu_cs_parser *p,
       }

       amdgpu_sync_create(&p->sync);
-     drm_exec_init(&p->exec, DRM_EXEC_INTERRUPTIBLE_WAIT);
+     drm_exec_init(&p->exec, DRM_EXEC_INTERRUPTIBLE_WAIT, 0);
       return 0;
   }

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c
index 720011019741..796fa6f1420b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_csa.c
@@ -70,7 +70,7 @@ int amdgpu_map_static_csa(struct amdgpu_device *adev, struct amdgpu_vm *vm,
       struct drm_exec exec;
       int r;

-     drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT);
+     drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT, 0);
       drm_exec_until_all_locked(&exec) {
               r = amdgpu_vm_lock_pd(vm, &exec, 0);
               if (likely(!r))
@@ -110,7 +110,7 @@ int amdgpu_unmap_static_csa(struct amdgpu_device *adev, struct amdgpu_vm *vm,
       struct drm_exec exec;
       int r;

-     drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT);
+     drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT, 0);
       drm_exec_until_all_locked(&exec) {
               r = amdgpu_vm_lock_pd(vm, &exec, 0);
               if (likely(!r))
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
index ca4d2d430e28..16f1715148ad 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
@@ -203,7 +203,7 @@ static void amdgpu_gem_object_close(struct drm_gem_object *obj,
       struct drm_exec exec;
       long r;

-     drm_exec_init(&exec, DRM_EXEC_IGNORE_DUPLICATES);
+     drm_exec_init(&exec, DRM_EXEC_IGNORE_DUPLICATES, 0);
       drm_exec_until_all_locked(&exec) {
               r = drm_exec_prepare_obj(&exec, &bo->tbo.base, 1);
               drm_exec_retry_on_contention(&exec);
@@ -739,7 +739,7 @@ int amdgpu_gem_va_ioctl(struct drm_device *dev, void *data,
       }

       drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT |
-                   DRM_EXEC_IGNORE_DUPLICATES);
+                   DRM_EXEC_IGNORE_DUPLICATES, 0);
       drm_exec_until_all_locked(&exec) {
               if (gobj) {
                       r = drm_exec_lock_obj(&exec, gobj);
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
index b6015157763a..3c351941701e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
@@ -1105,7 +1105,7 @@ int amdgpu_mes_ctx_map_meta_data(struct amdgpu_device *adev,

       amdgpu_sync_create(&sync);

-     drm_exec_init(&exec, 0);
+     drm_exec_init(&exec, 0, 0);
       drm_exec_until_all_locked(&exec) {
               r = drm_exec_lock_obj(&exec,
                                     &ctx_data->meta_data_obj->tbo.base);
@@ -1176,7 +1176,7 @@ int amdgpu_mes_ctx_unmap_meta_data(struct amdgpu_device *adev,
       struct drm_exec exec;
       long r;

-     drm_exec_init(&exec, 0);
+     drm_exec_init(&exec, 0, 0);
       drm_exec_until_all_locked(&exec) {
               r = drm_exec_lock_obj(&exec,
                                     &ctx_data->meta_data_obj->tbo.base);
diff --git a/drivers/gpu/drm/drm_exec.c b/drivers/gpu/drm/drm_exec.c
index 5d2809de4517..27d11c20d148 100644
--- a/drivers/gpu/drm/drm_exec.c
+++ b/drivers/gpu/drm/drm_exec.c
@@ -69,16 +69,25 @@ static void drm_exec_unlock_all(struct drm_exec *exec)
    * drm_exec_init - initialize a drm_exec object
    * @exec: the drm_exec object to initialize
    * @flags: controls locking behavior, see DRM_EXEC_* defines
+ * @nr: the initial # of objects
    *
    * Initialize the object and make sure that we can track locked objects.
+ *
+ * If nr is non-zero then it is used as the initial objects table size.
+ * In either case, the table will grow (be re-allocated) on demand.
    */
-void drm_exec_init(struct drm_exec *exec, uint32_t flags)
+void drm_exec_init(struct drm_exec *exec, uint32_t flags, unsigned nr)
   {
+     size_t sz = PAGE_SIZE;
+
+     if (nr)
+             sz = (size_t)nr * sizeof(void *);
+
       exec->flags = flags;
-     exec->objects = kmalloc(PAGE_SIZE, GFP_KERNEL);
+     exec->objects = kmalloc(sz, GFP_KERNEL);

Please use k*v*malloc() here since we can't predict how large that will be.

or __GFP_NOWARN?  If userspace (or kasan) is cheeky and asks for ~0
objects, we should probably just fail?
Oh, good point! If this value is controlled by userspace we must be much more careful.
Instead of __GFP_NOWARN or any other workaround we should use kvmalloc_array() here. 

Maybe turn the code upside down, in other words something like this here:

if (!nr)
    nr = PAGE_SIZE / sizeof(void *);

exec->objects = kvmalloc_array(nr, sizeof(void *), GFP_KERNEL);
exec->max_objects = exec->objects ? nr : 0;


Regards,
Christian.



BR,
-R


With that fixed the patch is Reviewed-by: Christian König
<christian.koenig@xxxxxxx>.

Regards,
Christian.


       /* If allocation here fails, just delay that till the first use */
-     exec->max_objects = exec->objects ? PAGE_SIZE / sizeof(void *) : 0;
+     exec->max_objects = exec->objects ? sz / sizeof(void *) : 0;
       exec->num_objects = 0;
       exec->contended = DRM_EXEC_DUMMY;
       exec->prelocked = NULL;
diff --git a/drivers/gpu/drm/nouveau/nouveau_exec.c b/drivers/gpu/drm/nouveau/nouveau_exec.c
index 19024ce21fbb..f5930cc0b3fb 100644
--- a/drivers/gpu/drm/nouveau/nouveau_exec.c
+++ b/drivers/gpu/drm/nouveau/nouveau_exec.c
@@ -103,7 +103,7 @@ nouveau_exec_job_submit(struct nouveau_job *job)

       nouveau_uvmm_lock(uvmm);
       drm_exec_init(exec, DRM_EXEC_INTERRUPTIBLE_WAIT |
-                         DRM_EXEC_IGNORE_DUPLICATES);
+                         DRM_EXEC_IGNORE_DUPLICATES, 0);
       drm_exec_until_all_locked(exec) {
               struct drm_gpuva *va;

diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
index aae780e4a4aa..3a9331a1c830 100644
--- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
@@ -1288,7 +1288,7 @@ nouveau_uvmm_bind_job_submit(struct nouveau_job *job)
       }

       drm_exec_init(exec, DRM_EXEC_INTERRUPTIBLE_WAIT |
-                         DRM_EXEC_IGNORE_DUPLICATES);
+                         DRM_EXEC_IGNORE_DUPLICATES, 0);
       drm_exec_until_all_locked(exec) {
               list_for_each_op(op, &bind_job->ops) {
                       struct drm_gpuva_op *va_op;
diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h
index b5bf0b6da791..f1a66c048721 100644
--- a/include/drm/drm_exec.h
+++ b/include/drm/drm_exec.h
@@ -135,7 +135,7 @@ static inline bool drm_exec_is_contended(struct drm_exec *exec)
       return !!exec->contended;
   }

-void drm_exec_init(struct drm_exec *exec, uint32_t flags);
+void drm_exec_init(struct drm_exec *exec, uint32_t flags, unsigned nr);
   void drm_exec_fini(struct drm_exec *exec);
   bool drm_exec_cleanup(struct drm_exec *exec);
   int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj);
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