[PATCH v2] drm/i915/gvt: Make MI_USER_INTERRUPT nop in cmd parser

[Tian, Kevin]

> From: Zhipeng Gong
> Sent: Monday, March 26, 2018 3:19 PM
> 
> GVT-g dispatches request to host i915 and depends on i915 notify
> ring interrupt mechanism to check completion of request.
> For now MI_USER_INTERRUPT in guest requests is passed through
> in GVT-g cmd parser and i915 does not use it, which causes
> unnecessary interrupt handling in i915.
> On the other hand, if several requests from guest are combined into
> one request in and contain MI_USER_INTERRUPT in the middle of
> combined request. GVT-g still has to wait on the whole request to
> complete to inject user interrupts to guest.
> 
> This patch makes all the MI_USER_INTERRUPT nop to save some interrupt
> handling.
> 
> Here is test result to run glmark2 on guest for 10 seconds:
> host master interrupts number is reduced from 16021 to 11162
> host user interrupts number is reduced from 7936 to 3536
> 
> v2:
> - revise commit message. (Kevin)
> 
> Signed-off-by: Zhipeng Gong <zhipeng.gong at intel.com>

Reviewed-by: Kevin Tian <kevin.tian at intel.com>