linux-kernel - Re: [Intel-gfx] [PATCH v3 6/6] drm/i915/gt: describe the new tlb parameter at i915_vma

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Message-ID: <YuFJtzTmyRZLwwK7@alfio.lan>
Date:   Wed, 27 Jul 2022 16:20:39 +0200
From:   Andi Shyti <andi.shyti@...ux.intel.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     David Airlie <airlied@...ux.ie>, intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Rodrigo Vivi <rodrigo.vivi@...el.com>
Subject: Re: [Intel-gfx] [PATCH v3 6/6] drm/i915/gt: describe the new tlb
 parameter at i915_vma_resource

Hi Mauro,

> TLB cache invalidation can happen on two different situations:
> 
> 1. synchronously, at __vma_put_pages();
> 2. asynchronously.
> 
> On the first case, TLB cache invalidation happens inside
> __vma_put_pages(). So, no need to do it later on.
> 
> However, on the second case, the pages will keep in memory
> until __i915_vma_evict() is called.
> 
> So, we need to store the TLB data at struct i915_vma_resource,
> in order to do a TLB cache invalidation before allowing
> userspace to re-use the same memory.
> 
> So, i915_vma_resource_unbind() has gained a new parameter
> in order to store the TLB data at the second case.
> 
> Document it.
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab@...nel.org>
> ---
> 
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH v3 0/6] at: https://lore.kernel.org/all/cover.1658924372.git.mchehab@kernel.org/
> 
>  drivers/gpu/drm/i915/i915_vma_resource.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_vma_resource.c b/drivers/gpu/drm/i915/i915_vma_resource.c
> index 5a67995ea5fe..4fe09ea0a825 100644
> --- a/drivers/gpu/drm/i915/i915_vma_resource.c
> +++ b/drivers/gpu/drm/i915/i915_vma_resource.c
> @@ -216,6 +216,10 @@ i915_vma_resource_fence_notify(struct i915_sw_fence *fence,
>  /**
>   * i915_vma_resource_unbind - Unbind a vma resource
>   * @vma_res: The vma resource to unbind.
> + * @tlb: pointer to vma->obj->mm.tlb associated with the resource
> + *	 to be stored at vma_res->tlb. When not-NULL, it will be used
> + *	 to do TLB cache invalidation before freeing a VMA resource.
> + *	 used only for async unbind.

/used/Used/

With that:

Reviewed-by: Andi Shyti <andi.shyti@...ux.intel.com>

Thanks,
Andi