[PATCH] drm/amdgpu: Fix incorrect return value

[Zhou1, Tao]

[AMD Official Use Only - General]

> -----Original Message-----
> From: Chai, Thomas <YiPeng.Chai at amd.com>
> Sent: Wednesday, April 3, 2024 3:07 PM
> To: amd-gfx at lists.freedesktop.org
> Cc: Chai, Thomas <YiPeng.Chai at amd.com>; Zhang, Hawking
> <Hawking.Zhang at amd.com>; Zhou1, Tao <Tao.Zhou1 at amd.com>; Li, Candice
> <Candice.Li at amd.com>; Wang, Yang(Kevin) <KevinYang.Wang at amd.com>; Yang,
> Stanley <Stanley.Yang at amd.com>; Chai, Thomas <YiPeng.Chai at amd.com>
> Subject: [PATCH] drm/amdgpu: Fix incorrect return value
>
> [Why]
>   After calling amdgpu_vram_mgr_reserve_range multiple times with the same
> address, calling amdgpu_vram_mgr_query_page_status will always return -
> EBUSY.
>   From the second call to amdgpu_vram_mgr_reserve_range, the same address
> will be added to the reservations_pending list again and is never moved to the
> reserved_pages list because the address had been reserved.
>
> [How]
>   First add the address status check before calling
> amdgpu_vram_mgr_do_reserve, if the address is already reserved, do nothing; If
> the address is already in the reservations_pending list, directly reserve memory;
> only add new nodes for the addresses that are not in the reserved_pages list and
> reservations_pending list.
>
> Signed-off-by: YiPeng Chai <YiPeng.Chai at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 28 +++++++++++++-------
>  1 file changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> index 1e36c428d254..0bf3f4092900 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> @@ -317,7 +317,6 @@ static void amdgpu_vram_mgr_do_reserve(struct
> ttm_resource_manager *man)
>
>               dev_dbg(adev->dev, "Reservation 0x%llx - %lld, Succeeded\n",
>                       rsv->start, rsv->size);
> -
>               vis_usage = amdgpu_vram_mgr_vis_size(adev, block);
>               atomic64_add(vis_usage, &mgr->vis_usage);
>               spin_lock(&man->bdev->lru_lock);
> @@ -340,19 +339,30 @@ int amdgpu_vram_mgr_reserve_range(struct
> amdgpu_vram_mgr *mgr,
>                                 uint64_t start, uint64_t size)
>  {
>       struct amdgpu_vram_reservation *rsv;
> +     int ret = 0;
>
> -     rsv = kzalloc(sizeof(*rsv), GFP_KERNEL);
> -     if (!rsv)
> -             return -ENOMEM;
> +     ret = amdgpu_vram_mgr_query_page_status(mgr, start);
> +     if (!ret)
> +             return 0;
> +
> +     if (ret == -ENOENT) {
> +             rsv = kzalloc(sizeof(*rsv), GFP_KERNEL);
> +             if (!rsv)
> +                     return -ENOMEM;
>
> -     INIT_LIST_HEAD(&rsv->allocated);
> -     INIT_LIST_HEAD(&rsv->blocks);
> +             INIT_LIST_HEAD(&rsv->allocated);
> +             INIT_LIST_HEAD(&rsv->blocks);
>
> -     rsv->start = start;
> -     rsv->size = size;
> +             rsv->start = start;
> +             rsv->size = size;
> +
> +             mutex_lock(&mgr->lock);
> +             list_add_tail(&rsv->blocks, &mgr->reservations_pending);
> +             mutex_unlock(&mgr->lock);

[Tao] we can drop the mutex_unlock and add if (ret != -ENOENT) for the second mutex_lock to avoid unlocking/locking repeatedly.

> +
> +     }
>
>       mutex_lock(&mgr->lock);
> -     list_add_tail(&rsv->blocks, &mgr->reservations_pending);
>       amdgpu_vram_mgr_do_reserve(&mgr->manager);
>       mutex_unlock(&mgr->lock);
>
> --
> 2.34.1