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Date:   Mon, 30 Oct 2023 17:01:16 +0100
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Subject: Re: [PATCH 6/7] drm/exec: Pass in initial # of objects
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To:     Rob Clark <robdclark@gmail.com>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>
Cc:     Kefeng Wang <wangkefeng.wang@huawei.com>,
        Karol Herbst <kherbst@redhat.com>,
        "open list:DRM DRIVER FOR NVIDIA GEFORCE/QUADRO GPUS" 
        <nouveau@lists.freedesktop.org>, dri-devel@lists.freedesktop.org,
        Mario Limonciello <mario.limonciello@amd.com>,
        Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>,
        David Airlie <airlied@gmail.com>,
        Rob Clark <robdclark@chromium.org>,
        Guchun Chen <guchun.chen@amd.com>,
        Shashank Sharma <shashank.sharma@amd.com>,
        "open list:RADEON and AMDGPU DRM DRIVERS" 
        <amd-gfx@lists.freedesktop.org>,
        Dong Chenchen <dongchenchen2@huawei.com>,
        Luben Tuikov <luben.tuikov@amd.com>,
        Philip Yang <Philip.Yang@amd.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>,
        linux-arm-msm@vger.kernel.org,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Suren Baghdasaryan <surenb@google.com>,
        Jack Xiao <Jack.Xiao@amd.com>,
        Jonathan Kim <jonathan.kim@amd.com>,
        freedreno@lists.freedesktop.org,
        Felix Kuehling <Felix.Kuehling@amd.com>,
        "Pan, Xinhui" <Xinhui.Pan@amd.com>,
        open list <linux-kernel@vger.kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Alex Deucher <alexander.deucher@amd.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Lang Yu <Lang.Yu@amd.com>
References: <20231027165859.395638-1-robdclark@gmail.com>
 <20231027165859.395638-7-robdclark@gmail.com>
 <597b5bb3-ca75-4662-9904-12c4d8e9101a@amd.com>
 <CAF6AEGu1Z1k0bKrMZw4-RJSC-nbO=tuDOjQiPmi61_m_1nRCgA@mail.gmail.com>
From:   =?UTF-8?Q?Christian_K=C3=B6nig?= <ckoenig.leichtzumerken@gmail.com>
In-Reply-To: <CAF6AEGu1Z1k0bKrMZw4-RJSC-nbO=tuDOjQiPmi61_m_1nRCgA@mail.gmail.com>
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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@amd.com> wrote:
>> Am 27.10.23 um 18:58 schrieb Rob Clark:
>>> From: Rob Clark <robdclark@chromium.org>
>>>
>>> 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@chromium.org>
>>> ---
>>>    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@amd.com>.
>>
>> 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);