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  1. Bug #1917813
  2. Comment #32

Comment 32 for bug 1917813

Revision history for this message
In , dsmythies (dsmythies-linux-kernel-bugs) wrote :

(In reply to Doug Smythies from comment #28)
> Created attachment 295533 [details]
> changing the MWAIT definition of C1E fixes the problem

Conversely, I have tried to determine if other idle states can be broken by introducing the least significant bit of the MWAIT.

I did idle state 3, C3, and could not detect any change in system response.

I did idle state 5, C7S, which already had the bit set, along with bit 1, so I set bit one to 0:

  .name = "C7s",
- .desc = "MWAIT 0x33",
- .flags = MWAIT2flg(0x33) | CPUIDLE_FLAG_TLB_FLUSHED,
+ .desc = "MWAIT 0x31",
+ .flags = MWAIT2flg(0x31) | CPUIDLE_FLAG_TLB_FLUSHED,
  .exit_latency = 124,
  .target_residency = 800,
  .enter = &intel_idle,

I could not detect any change in system response.

I am also unable to detect any difference in system response between idle state 1, C1, and idle state 2, C1E, with this change. I do not know if the change merely makes idle state 2 = idle state 1.