[PATCH] drm/i915/gvt: cancel dma map only for not present ggtt entry

[Zhenyu Wang]

On 2019.05.15 14:05:59 +0800, Xiaolin Zhang wrote:
> only cancel ggtt entry dma map for invalid ggtt entry, don't do it
> for paritial update or old ggtt entry.
> 
> this change can address DMA "fault reason 23" issue for win guest with
> intel iommu on.
> 
> Signed-off-by: Xiaolin Zhang <xiaolin.zhang at intel.com>
> ---
>  drivers/gpu/drm/i915/gvt/gtt.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
> index c2f7d20f6346..6d021d830f37 100644
> --- a/drivers/gpu/drm/i915/gvt/gtt.c
> +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> @@ -2243,7 +2243,12 @@ static int emulate_ggtt_mmio_write(struct intel_vgpu *vgpu, unsigned int off,
>  		}
>  	}
>  
> -	if (!partial_update && (ops->test_present(&e))) {
> +	if (!ops->test_present(&e)) {
> +		ggtt_get_host_entry(ggtt_mm, &m, g_gtt_index);
> +		ggtt_invalidate_pte(vgpu, &m);
> +		ops->set_pfn(&m, gvt->gtt.scratch_mfn);
> +		ops->clear_present(&m);
> +	} else if (!partial_update && (ops->test_present(&e))) {
>  		gfn = ops->get_pfn(&e);
>  		m = e;

I think this makes condition check a bit cumbersome, as the special case
you need to handle is for partial_update instead of test_present.

>  
> @@ -2266,19 +2271,11 @@ static int emulate_ggtt_mmio_write(struct intel_vgpu *vgpu, unsigned int off,
>  			ops->set_pfn(&m, gvt->gtt.scratch_mfn);
>  		} else
>  			ops->set_pfn(&m, dma_addr >> PAGE_SHIFT);
> -	} else {
> -		ops->set_pfn(&m, gvt->gtt.scratch_mfn);
> -		ops->clear_present(&m);
>  	}
> -
>  out:
> -	ggtt_set_guest_entry(ggtt_mm, &e, g_gtt_index);
> -
> -	ggtt_get_host_entry(ggtt_mm, &e, g_gtt_index);
> -	ggtt_invalidate_pte(vgpu, &e);

Can we do unmap for !partial_update only and remove above clear_present?
So still use scratch for host in case of partial update.

> -
>  	ggtt_set_host_entry(ggtt_mm, &m, g_gtt_index);
>  	ggtt_invalidate(gvt->dev_priv);
> +	ggtt_set_guest_entry(ggtt_mm, &e, g_gtt_index);
>  	return 0;
>  }
>  
> -- 
> 2.15.1
> 

-- 
Open Source Technology Center, Intel ltd.

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