linux-kernel - Re: [PATCH v2 2/4] drm/ttm: Don't shadow the operation context

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Message-ID: <88cbec2d2ae6329d44426cece4b558b7d83b1ff6.camel@linux.intel.com>
Date:   Mon, 26 Jun 2023 17:18:16 +0200
From:   Thomas Hellström 
        <thomas.hellstrom@...ux.intel.com>
To:     Christian König 
        <ckoenig.leichtzumerken@...il.com>, intel-xe@...ts.freedesktop.org
Cc:     Christian König <christian.koenig@....com>,
        Roger He <Hongbo.He@....com>, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, stable@...r.kernel.org,
        Matthew Brost <matthew.brost@...el.com>,
        linux-kernel@...r.kernel.org,
        Andi Shyti <andi.shyti@...ux.intel.com>
Subject: Re: [PATCH v2 2/4] drm/ttm: Don't shadow the operation context

On Mon, 2023-06-26 at 17:15 +0200, Christian König wrote:
> Am 26.06.23 um 11:14 schrieb Thomas Hellström:
> > ttm_bo_swapout() shadows the ttm operation context which may cause
> > major confusion in driver callbacks when swapping out
> > !TTM_PL_SYSTEM
> > memory. Fix this by reusing the operation context argument to
> > ttm_bo_swapout().
> > 
> > Cc: "Christian König" <christian.koenig@....com>
> > Cc: Roger He <Hongbo.He@....com>
> > Cc: <dri-devel@...ts.freedesktop.org>
> > Cc: <intel-gfx@...ts.freedesktop.org>
> > Cc: <stable@...r.kernel.org> # v4.16+
> > Fixes: dc947770cf34 ("drm/ttm: enable swapout for reserved BOs
> > during allocation")
> > Signed-off-by: Thomas Hellström <thomas.hellstrom@...ux.intel.com>
> > Acked-by: Matthew Brost <matthew.brost@...el.com>
> 
> We intentionally didn't used the parameter here, but I absolutely
> can't 
> figure out why.
> 
> Feel free to add my rb, but let's give it some time upstream before
> you 
> base anything on top of this. Just in case we missed something.

Sure. Thanks for reviewing,
/Thomas

> 
> Regards,
> Christian.
> 
> > ---
> >   drivers/gpu/drm/ttm/ttm_bo.c | 3 +--
> >   1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c
> > b/drivers/gpu/drm/ttm/ttm_bo.c
> > index bd5dae4d1624..615d30c4262d 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> > @@ -1154,7 +1154,6 @@ int ttm_bo_swapout(struct ttm_buffer_object
> > *bo, struct ttm_operation_ctx *ctx,
> >          * Move to system cached
> >          */
> >         if (bo->resource->mem_type != TTM_PL_SYSTEM) {
> > -               struct ttm_operation_ctx ctx = { false, false };
> >                 struct ttm_resource *evict_mem;
> >                 struct ttm_place hop;
> >   
> > @@ -1164,7 +1163,7 @@ int ttm_bo_swapout(struct ttm_buffer_object
> > *bo, struct ttm_operation_ctx *ctx,
> >                 if (unlikely(ret))
> >                         goto out;
> >   
> > -               ret = ttm_bo_handle_move_mem(bo, evict_mem, true,
> > &ctx, &hop);
> > +               ret = ttm_bo_handle_move_mem(bo, evict_mem, true,
> > ctx, &hop);
> >                 if (unlikely(ret != 0)) {
> >                         WARN(ret == -EMULTIHOP, "Unexpected
> > multihop in swaput - likely driver bug.\n");
> >                         goto out;
>