RE: [GIT PULL] Additional x86 fixes for 2.6.31-rc5

Tan, Wei Chong
2009-08-05T23:10:22Z

> Sure, we might want the error term to be even smaller, but
> in no way does it actually invalidate any of the logic -
> the 'tsc' reading is just a guess anyway. Also, I think
> that the real issue isn't even an SMI - but the fact that
> in the very last iteration of the loop, there's no
> serializing instruction _after_ the last 'rdtsc'. So even
> in the absense of SMI's, we do have a situation where the
> cycle counter was read without proper serialization.
>

Hi,

I just recall something which I cannot understand. Earlier when we observed the wrong CPU frequency phenomenon (1666MHz being identified as 1800MHz), we use the same CPU and put them on 2 different boards. On one board, the failure rate is high (about 1 out of every 20). On the other, it almost never fails.
We compare the 2 boards and they are quite close to each other with one very prominent difference. The failing board has no PS/2 port and so is using all USB keyboard/mouse while the good board uses PS/2 keyboard/mouse.
Thus, we plug in a USB keyboard on the good board and were then able produce the failure on the good board (despite at a lower failure rate, 1 out of every 100).
Does this not point to SMI?

Regards,
Wei Chong.