[PATCH v7] drm/i915/gvt: skip populate shadow context if guest context not changed

[Zhenyu Wang]

On 2020.04.17 05:13:34 -0400, Yan Zhao wrote:
> Software is not expected to populate engine context except when using
> restore inhibit bit or golden state to initialize it for the first time.
> 
> Therefore, if a newly submitted guest context is the same as the last
> shadowed one, no need to populate its engine context from guest again.
> 
> Currently using lrca + ring_context_gpa to identify whether two guest
> contexts are the same.
> 
> The reason of why context id is not included as an identifier is that
> i915 recently changed the code and context id is only unique for a
> context when OA is enabled. And when OA is on, context id is generated
> based on lrca. Therefore, in that case, if two contexts are of the same
> lrca, they have identical context ids as well.
> (This patch also works with old guest kernel like 4.20.)
> 
> for guest context, if its ggtt entry is modified after last context
> shadowing, it is also deemed as not the same context as last shadowed one.
> 
> v7:
> -removed local variable "valid". use the one in s->last_ctx diretly
> 
> v6:
> -change type of lrca of last ctx to be u32. as currently it's all
> protected by vgpu lock (Kevin Tian)
> -reset valid of last ctx to false once it needs to be repopulated before
> population completes successfully (Kevin Tian)
> 
> v5:
> -merge all 3 patches into one patch  (Zhenyu Wang)
> 
> v4:
> - split the series into 3 patches.
> - don't turn on optimization until last patch in this series (Kevin Tian)
> - define lrca to be atomic in this patch rather than update its type in
> the second patch (Kevin Tian)
> 
> v3: updated commit message to describe engine context and context id
> clearly (Kevin Tian)
> v2: rebased to 5.6.0-rc4+Signed-off-by: Yan Zhao <yan.y.zhao at intel.com>
> 
> Reviewed-by: Zhenyu Wang <zhenyuw at linux.intel.com>
> Cc: Kevin Tian <kevin.tian at intel.com>
> Suggested-by: Zhenyu Wang <zhenyuw at linux.intel.com>
> Signed-off-by: Yan Zhao <yan.y.zhao at intel.com>
> ---

Applied. Thanks for the review!

-- 
Open Source Technology Center, Intel ltd.

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