[PATCH v2] drm/i915/gvt: cancel dma map only for not present ggtt entry

[Zhenyu Wang]

On 2019.05.15 16:19:21 +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.
> 
> v2: update handling of ggtt partial update (Zhenyu, Yan, Henry)
> 
> Signed-off-by: Xiaolin Zhang <xiaolin.zhang at intel.com>
> ---
>  drivers/gpu/drm/i915/gvt/gtt.c | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
> index c2f7d20f6346..4856b9fec411 100644
> --- a/drivers/gpu/drm/i915/gvt/gtt.c
> +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> @@ -2243,10 +2243,21 @@ 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 {
>  		gfn = ops->get_pfn(&e);
>  		m = e;
>  
> +		if (partial_update) {
> +			ops->set_pfn(&m, gvt->gtt.scratch_mfn);
> +			ops->clear_present(&m);
> +			goto out;
> +		}
> +
>  		/* one PTE update may be issued in multiple writes and the
>  		 * first write may not construct a valid gfn
>  		 */
> @@ -2266,17 +2277,9 @@ 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);
> -
>  	ggtt_set_host_entry(ggtt_mm, &m, g_gtt_index);
>  	ggtt_invalidate(gvt->dev_priv);
>  	return 0;
> -- 

How about below simpler change?

diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
index 08c74e65836b..8f27db9d7a1e 100644
--- a/drivers/gpu/drm/i915/gvt/gtt.c
+++ b/drivers/gpu/drm/i915/gvt/gtt.c
@@ -2269,16 +2269,16 @@ 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 {
+	} 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);
+	if (!partial_update) {
+		ggtt_get_host_entry(ggtt_mm, &e, g_gtt_index);
+		ggtt_invalidate_pte(vgpu, &e);
+	}
 
 	ggtt_set_host_entry(ggtt_mm, &m, g_gtt_index);
 	ggtt_invalidate(gvt->dev_priv);


-- 
Open Source Technology Center, Intel ltd.

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