igt@perf@gen12* - Writing to RING_CONTEXT_CONTROL causes spurious CS event

pstore7-1575916446_Panic_2.logpstore8-1559446454_Panic_2.log

<0>[  692.341701]     perf-1332    1.... 680728951us : __i915_request_commit: rcs0 fence 1d4f:4
<0>[  692.341749]   <idle>-0       7..s1 680729041us : process_csb: rcs0 cs-irq head=9, tail=11
<0>[  692.341802]   <idle>-0       7..s1 680729042us : process_csb: rcs0 csb[10]: status=0x00000001:0x03ff8000
<0>[  692.341851]   <idle>-0       7..s1 680729049us : trace_ports: rcs0: promote { 5:325702!, 0:0 }
<0>[  692.341898]   <idle>-0       7..s1 680729050us : process_csb: rcs0 csb[11]: status=0x03ff8000:0x00000000
<0>[  692.341946]   <idle>-0       7..s1 680729051us : trace_ports: rcs0: completed { 5:325702!, 0:0 }
<0>[  692.341999]   <idle>-0       7dNs2 680729061us : __i915_request_submit: rcs0 fence 1d4f:4, current 2
<0>[  692.342049]   <idle>-0       7dNs2 680729063us : __execlists_submission_tasklet: rcs0: queue_priority_hint:-2147483648, submit:yes
<0>[  692.342115]   <idle>-0       7dNs2 680729064us : trace_ports: rcs0: submit { 1d4f:4, 0:0 }
<0>[  692.342167] kworker/-47      7.... 680729077us : i915_request_retire: rcs0 fence 5:325700, current 325702
<0>[  692.342245] kworker/-47      7..s1 680729096us : process_csb: rcs0 cs-irq head=11, tail=0
<0>[  692.342313] kworker/-47      7..s1 680729096us : process_csb: rcs0 csb[0]: status=0x03ff8001:0x03ff8000
<0>[  692.342365] kworker/-47      7..s1 680729134us : process_csb: gen12_csb_parse:2091 GEM_BUG_ON(!ctx_to_valid)