RE: [PATCH] drm/ttm: fix deref of bo->ttm without holding the lock v2

["Huang, Ray" <Ray.Huang@amd.com>]

Looks good for me.

Reviewed-by: Huang Rui <ray.huang@amd.com>

-----Original Message-----
From: Christian König <ckoenig.leichtzumerken@gmail.com> 
Sent: Monday, June 7, 2021 8:52 PM
To: dri-devel@lists.freedesktop.org; Pan, Xinhui <Xinhui.Pan@amd.com>; Das, Nirmoy <Nirmoy.Das@amd.com>; Huang, Ray <Ray.Huang@amd.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Subject: Re: [PATCH] drm/ttm: fix deref of bo->ttm without holding the lock v2



Am 28.05.21 um 15:06 schrieb Thomas Hellström:
>
> On 5/28/21 3:00 PM, Christian König wrote:
>> We need to grab the resv lock first before doing that check.
>>
>> v2 (chk): simplify the change for -fixes
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>
> Hmm, OK, but this doesn't fix the swapped-bo-not-on-lru and 
> unpopulating from swap_notify issues. Are you planning a follow up 
> patch for those?

As discussed in a separate thread this needs to be applied as needed when the DG1 branch is merged.

Xinhui, Nirmoy, Rui can anybody give be an rb/ab so that I can push this?

Thanks,
Christian.

>
> Thanks,
>
> Thomas
>
>> ---
>>   drivers/gpu/drm/ttm/ttm_bo.c     | 5 ++++-
>>   drivers/gpu/drm/ttm/ttm_device.c | 8 +-------
>>   2 files changed, 5 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c 
>> b/drivers/gpu/drm/ttm/ttm_bo.c index cfd0b9292397..ebcffe794adb 
>> 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>> @@ -1172,7 +1172,10 @@ int ttm_bo_swapout(struct ttm_buffer_object 
>> *bo, struct ttm_operation_ctx *ctx,
>>       if (!ttm_bo_evict_swapout_allowable(bo, ctx, &locked, NULL))
>>           return -EBUSY;
>>   -    if (!ttm_bo_get_unless_zero(bo)) {
>> +    if (!bo->ttm || !ttm_tt_is_populated(bo->ttm) ||
>> +        bo->ttm->page_flags & TTM_PAGE_FLAG_SG ||
>> +        bo->ttm->page_flags & TTM_PAGE_FLAG_SWAPPED ||
>> +        !ttm_bo_get_unless_zero(bo)) {
>>           if (locked)
>>               dma_resv_unlock(bo->base.resv);
>>           return -EBUSY;
>> diff --git a/drivers/gpu/drm/ttm/ttm_device.c
>> b/drivers/gpu/drm/ttm/ttm_device.c
>> index a1dcf7d55c90..3d9c62b93e29 100644
>> --- a/drivers/gpu/drm/ttm/ttm_device.c
>> +++ b/drivers/gpu/drm/ttm/ttm_device.c
>> @@ -143,14 +143,8 @@ int ttm_device_swapout(struct ttm_device *bdev, 
>> struct ttm_operation_ctx *ctx,
>>             for (j = 0; j < TTM_MAX_BO_PRIORITY; ++j) {
>>               list_for_each_entry(bo, &man->lru[j], lru) {
>> -                uint32_t num_pages;
>> +                uint32_t num_pages = PFN_UP(bo->base.size);
>>   -                if (!bo->ttm || !ttm_tt_is_populated(bo->ttm) ||
>> -                    bo->ttm->page_flags & TTM_PAGE_FLAG_SG ||
>> -                    bo->ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)
>> -                    continue;
>> -
>> -                num_pages = bo->ttm->num_pages;
>>                   ret = ttm_bo_swapout(bo, ctx, gfp_flags);
>>                   /* ttm_bo_swapout has dropped the lru_lock */
>>                   if (!ret)