From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A091521147B for ; Wed, 5 Mar 2025 10:30:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741170624; cv=none; b=IEnUzS1fKe3Sx4cSy8hIfxwdAi/wTj9k9Yp5jMIW/hHAFsqXVg6A3jpYw6Ms/PsEktcDyRZYyksDMV1Ukl1f6Kp57jmL5o9xokG/Ay9M3fVrO09TjrVRM/gw+SU7YuyHxdZ0ai54mb4p3gd7DoIDCOjBIdyz7LtKVYvP8g1dazg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741170624; c=relaxed/simple; bh=PAvmWz1PFQmaSlup+6X0UngFEKHUKJvNzD6IL6zjxG8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mtZnneeMVYTzyuYXCh0Wq+XfWfFiVJujX2K2lN6+ASTQI2zpBmJDeeVgdBFUcEDgkLmmp5xIx9MCqIRBZsGec0SGn5kPz50edzPzYKghapoBuPYor7Bm9E7rlE+PzeaG7piemwXI4seVx8PBJ9khuuZI8laBqiLySUMehZ97BZI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 395F9FEC; Wed, 5 Mar 2025 02:30:34 -0800 (PST) Received: from [10.57.67.16] (unknown [10.57.67.16]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B565D3F673; Wed, 5 Mar 2025 02:30:18 -0800 (PST) Message-ID: <6506d660-cbb6-42b6-893e-25ded19c5f11@arm.com> Date: Wed, 5 Mar 2025 10:30:17 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/2] drm/panthor: Avoid sleep locking in the internal BO size path To: =?UTF-8?Q?Adri=C3=A1n_Larumbe?= , Boris Brezillon , Liviu Dudau , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Mihail Atanassov Cc: kernel@collabora.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20250303190923.1639985-1-adrian.larumbe@collabora.com> <20250303190923.1639985-2-adrian.larumbe@collabora.com> From: Steven Price Content-Language: en-GB In-Reply-To: <20250303190923.1639985-2-adrian.larumbe@collabora.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 03/03/2025 19:08, Adrián Larumbe wrote: > Commit 434e5ca5b5d7 ("drm/panthor: Expose size of driver internal BO's over > fdinfo") locks the VMS xarray, to avoid UAF errors when the same VM is > being concurrently destroyed by another thread. However, that puts the > current thread in atomic context, which means taking the VMS' heap locks > will trigger a warning as the thread is no longer allowed to sleep. > > Because in this case replacing the heap mutex with a spinlock isn't > feasible, the fdinfo handler no longer traverses the list of heaps for > every single VM associated with an open DRM file. Instead, when a new heap > chunk is allocated, its size is accumulated into a pool-wide tally, which > also makes the atomic context code path somewhat faster. > > Signed-off-by: Adrián Larumbe > Fixes: 3e2c8c718567 ("drm/panthor: Expose size of driver internal BO's over fdinfo") Reviewed-by: Steven Price > --- > drivers/gpu/drm/panthor/panthor_heap.c | 62 +++++++++++++------------- > drivers/gpu/drm/panthor/panthor_mmu.c | 8 +--- > 2 files changed, 31 insertions(+), 39 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_heap.c b/drivers/gpu/drm/panthor/panthor_heap.c > index db0285ce5812..3bdf61c14264 100644 > --- a/drivers/gpu/drm/panthor/panthor_heap.c > +++ b/drivers/gpu/drm/panthor/panthor_heap.c > @@ -97,6 +97,9 @@ struct panthor_heap_pool { > > /** @gpu_contexts: Buffer object containing the GPU heap contexts. */ > struct panthor_kernel_bo *gpu_contexts; > + > + /** @size: Size of all chunks across all heaps in the pool. */ > + atomic_t size; > }; > > static int panthor_heap_ctx_stride(struct panthor_device *ptdev) > @@ -118,7 +121,7 @@ static void *panthor_get_heap_ctx(struct panthor_heap_pool *pool, int id) > panthor_get_heap_ctx_offset(pool, id); > } > > -static void panthor_free_heap_chunk(struct panthor_vm *vm, > +static void panthor_free_heap_chunk(struct panthor_heap_pool *pool, > struct panthor_heap *heap, > struct panthor_heap_chunk *chunk) > { > @@ -127,12 +130,13 @@ static void panthor_free_heap_chunk(struct panthor_vm *vm, > heap->chunk_count--; > mutex_unlock(&heap->lock); > > + atomic_sub(heap->chunk_size, &pool->size); > + > panthor_kernel_bo_destroy(chunk->bo); > kfree(chunk); > } > > -static int panthor_alloc_heap_chunk(struct panthor_device *ptdev, > - struct panthor_vm *vm, > +static int panthor_alloc_heap_chunk(struct panthor_heap_pool *pool, > struct panthor_heap *heap, > bool initial_chunk) > { > @@ -144,7 +148,7 @@ static int panthor_alloc_heap_chunk(struct panthor_device *ptdev, > if (!chunk) > return -ENOMEM; > > - chunk->bo = panthor_kernel_bo_create(ptdev, vm, heap->chunk_size, > + chunk->bo = panthor_kernel_bo_create(pool->ptdev, pool->vm, heap->chunk_size, > DRM_PANTHOR_BO_NO_MMAP, > DRM_PANTHOR_VM_BIND_OP_MAP_NOEXEC, > PANTHOR_VM_KERNEL_AUTO_VA); > @@ -180,6 +184,8 @@ static int panthor_alloc_heap_chunk(struct panthor_device *ptdev, > heap->chunk_count++; > mutex_unlock(&heap->lock); > > + atomic_add(heap->chunk_size, &pool->size); > + > return 0; > > err_destroy_bo: > @@ -191,17 +197,16 @@ static int panthor_alloc_heap_chunk(struct panthor_device *ptdev, > return ret; > } > > -static void panthor_free_heap_chunks(struct panthor_vm *vm, > +static void panthor_free_heap_chunks(struct panthor_heap_pool *pool, > struct panthor_heap *heap) > { > struct panthor_heap_chunk *chunk, *tmp; > > list_for_each_entry_safe(chunk, tmp, &heap->chunks, node) > - panthor_free_heap_chunk(vm, heap, chunk); > + panthor_free_heap_chunk(pool, heap, chunk); > } > > -static int panthor_alloc_heap_chunks(struct panthor_device *ptdev, > - struct panthor_vm *vm, > +static int panthor_alloc_heap_chunks(struct panthor_heap_pool *pool, > struct panthor_heap *heap, > u32 chunk_count) > { > @@ -209,7 +214,7 @@ static int panthor_alloc_heap_chunks(struct panthor_device *ptdev, > u32 i; > > for (i = 0; i < chunk_count; i++) { > - ret = panthor_alloc_heap_chunk(ptdev, vm, heap, true); > + ret = panthor_alloc_heap_chunk(pool, heap, true); > if (ret) > return ret; > } > @@ -226,7 +231,7 @@ panthor_heap_destroy_locked(struct panthor_heap_pool *pool, u32 handle) > if (!heap) > return -EINVAL; > > - panthor_free_heap_chunks(pool->vm, heap); > + panthor_free_heap_chunks(pool, heap); > mutex_destroy(&heap->lock); > kfree(heap); > return 0; > @@ -308,8 +313,7 @@ int panthor_heap_create(struct panthor_heap_pool *pool, > heap->max_chunks = max_chunks; > heap->target_in_flight = target_in_flight; > > - ret = panthor_alloc_heap_chunks(pool->ptdev, vm, heap, > - initial_chunk_count); > + ret = panthor_alloc_heap_chunks(pool, heap, initial_chunk_count); > if (ret) > goto err_free_heap; > > @@ -342,7 +346,7 @@ int panthor_heap_create(struct panthor_heap_pool *pool, > return id; > > err_free_heap: > - panthor_free_heap_chunks(pool->vm, heap); > + panthor_free_heap_chunks(pool, heap); > mutex_destroy(&heap->lock); > kfree(heap); > > @@ -389,6 +393,7 @@ int panthor_heap_return_chunk(struct panthor_heap_pool *pool, > removed = chunk; > list_del(&chunk->node); > heap->chunk_count--; > + atomic_sub(heap->chunk_size, &pool->size); > break; > } > } > @@ -466,7 +471,7 @@ int panthor_heap_grow(struct panthor_heap_pool *pool, > * further jobs in this queue fail immediately instead of having to > * wait for the job timeout. > */ > - ret = panthor_alloc_heap_chunk(pool->ptdev, pool->vm, heap, false); > + ret = panthor_alloc_heap_chunk(pool, heap, false); > if (ret) > goto out_unlock; > > @@ -560,6 +565,8 @@ panthor_heap_pool_create(struct panthor_device *ptdev, struct panthor_vm *vm) > if (ret) > goto err_destroy_pool; > > + atomic_add(pool->gpu_contexts->obj->size, &pool->size); > + > return pool; > > err_destroy_pool: > @@ -594,8 +601,10 @@ void panthor_heap_pool_destroy(struct panthor_heap_pool *pool) > xa_for_each(&pool->xa, i, heap) > drm_WARN_ON(&pool->ptdev->base, panthor_heap_destroy_locked(pool, i)); > > - if (!IS_ERR_OR_NULL(pool->gpu_contexts)) > + if (!IS_ERR_OR_NULL(pool->gpu_contexts)) { > + atomic_sub(pool->gpu_contexts->obj->size, &pool->size); > panthor_kernel_bo_destroy(pool->gpu_contexts); > + } > > /* Reflects the fact the pool has been destroyed. */ > pool->vm = NULL; > @@ -605,27 +614,16 @@ void panthor_heap_pool_destroy(struct panthor_heap_pool *pool) > } > > /** > - * panthor_heap_pool_size() - Calculate size of all chunks across all heaps in a pool > - * @pool: Pool whose total chunk size to calculate. > + * panthor_heap_pool_size() - Get a heap pool's total size > + * @pool: Pool whose total chunks size to return > * > - * This function adds the size of all heap chunks across all heaps in the > - * argument pool. It also adds the size of the gpu contexts kernel bo. > - * It is meant to be used by fdinfo for displaying the size of internal > - * driver BO's that aren't exposed to userspace through a GEM handle. > + * Returns the aggregated size of all chunks for all heaps in the pool > * > */ > size_t panthor_heap_pool_size(struct panthor_heap_pool *pool) > { > - struct panthor_heap *heap; > - unsigned long i; > - size_t size = 0; > - > - down_read(&pool->lock); > - xa_for_each(&pool->xa, i, heap) > - size += heap->chunk_size * heap->chunk_count; > - up_read(&pool->lock); > - > - size += pool->gpu_contexts->obj->size; > + if (!pool) > + return 0; > > - return size; > + return atomic_read(&pool->size); > } > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c > index 8c6fc587ddc3..12a02e28f50f 100644 > --- a/drivers/gpu/drm/panthor/panthor_mmu.c > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c > @@ -1963,13 +1963,7 @@ void panthor_vm_heaps_sizes(struct panthor_file *pfile, struct drm_memory_stats > > xa_lock(&pfile->vms->xa); > xa_for_each(&pfile->vms->xa, i, vm) { > - size_t size = 0; > - > - mutex_lock(&vm->heaps.lock); > - if (vm->heaps.pool) > - size = panthor_heap_pool_size(vm->heaps.pool); > - mutex_unlock(&vm->heaps.lock); > - > + size_t size = panthor_heap_pool_size(vm->heaps.pool); > stats->resident += size; > if (vm->as.id >= 0) > stats->active += size;