[PATCH] drm/i915/gvt: set shadow entry to scratch page when guest driver only update partial of the GGTT entry

[Zhenyu Wang]

On 2017.03.21 17:59:28 +0800, Xiaoguang Chen wrote:
> Sometimes guest driver only update partial of GGTT entry then
> access it. In this situation the gfn we got from the GGTT table
> is invalid and can not be translate to a valid mfn.
> p2m translation should happen only when the whole parts of a
> GGTT entry got updated.
> 
> Setting the shadow entry pointing to a scratch page instead if only
> partial of GGTT entry updated.
> 
> Signed-off-by: Zhi Wang <zhi.a.wang at intel.com>
> SIgned-off-by: Xiaoguang Chen <xiaoguang.chen at intel.com
  ^^^^
  
ok, I might need to update with this new one, but pls use 'git commit -s'
for proper signed-off, use '-v N' to send with patch version, use '--in-reply-to'
with good threading.

>  drivers/gpu/drm/i915/gvt/gtt.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
> index da73127..119cd30 100644
> --- a/drivers/gpu/drm/i915/gvt/gtt.c
> +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> @@ -1837,11 +1837,21 @@ static int emulate_gtt_mmio_write(struct intel_vgpu *vgpu, unsigned int off,
>  		ret = gtt_entry_p2m(vgpu, &e, &m);
>  		if (ret) {
>  			gvt_vgpu_err("fail to translate guest gtt entry\n");
> -			return ret;
> +			/* guest driver may read/write the entry when only
> +			 * partial of the guest entry got updated.
> +			 * In this situation the gfn we got from GGTT table is
> +			 * invalid and can not be translated to a valid mfn.
> +			 * p2m translation should happen only after the whole
> +			 * parts of a GGTT entry got updated.
> +			 *
> +			 * Setting the shadow entry pointing to a scratch page
> +			 * instead while GGTT entry only got partial update.
> +			 */
> +			ops->set_pfn(&m, gvt->gtt.scratch_ggtt_mfn);
>  		}
>  	} else {
>  		m = e;
> -		m.val64 = 0;
> +		ops->set_pfn(&m, gvt->gtt.scratch_ggtt_mfn);
>  	}
>  
>  	ggtt_set_shadow_entry(ggtt_mm, &m, g_gtt_index);
> -- 
> 2.7.4
> 
> _______________________________________________
> intel-gvt-dev mailing list
> intel-gvt-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev

-- 
Open Source Technology Center, Intel ltd.

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