drm/i915/gvt: Prevent divided by zero when calculating refresh rate
To get refresh rate as vblank timer period and keep the precision, the calculation of rate is multiplied by 1000. However old logic was using: rate = pixel clock / (h * v / 1000). When the h/v total is invalid, like all 0, h * v / 1000 will be rounded to 0, which leads to a divided by 0 fault. 0 H/V are already checked above. Instead of divide after divide, refine the calculation to divide after multiply: "pixel clock * 1000 / (h * v)" Guest driver should guarantee the correctness of the timing regs' value. Fixes: 6a4500c7 ("drm/i915/gvt: Get accurate vGPU virtual display refresh rate from vreg") Reported-by:Zhenyu Wang <zhenyuw@linux.intel.com> Signed-off-by:
Colin Xu <colin.xu@intel.com> Signed-off-by:
Zhenyu Wang <zhenyuw@linux.intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20210416083355.159305-1-colin.xu@intel.com Reviewed-by:
Zhenyu Wang <zhenyuw@linux.intel.com>
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