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    SubjectRE: [PATCH] x86: Export tsc related information in sysfs
    On Mon, 17 May 2010, Dan Magenheimer wrote:
    >
    > OK, so let's invert the sense of the sysfs file and call it (for now)
    > "tsc_detected_as_UNreliable". Then anytime the kernel detects
    > a failed warp test (or any other suspicious condition), it changes
    > the bit from 0 to 1 effectively saying "if you are using rdtsc
    > against our recommendation, we told you that it might go bad and
    > it has, so consider yourself warned that some of the timestamps
    > you've taken since the last time you've checked this flag
    > may be b*rked"
    >
    > IMHO, addressing the issue directly and clearly documenting it
    > (instead of trying to hide the dirty laundry in the kernel)
    > will result in far better education of systems programmers
    > and far fewer end user problems. Which raises another good analogy:
    >
    > You are telling teenagers to abstain and I am proposing that we
    > instead encourage them to use a condom.

    Wrong. A vsyscall _is_ the protection which you want them to pull over
    the rdtsc.

    You are basically telling them: Go ahead, but keep in mind to look for
    that well hidden tag behind the left earlobe which might change
    suddenly from "no disease" to "infectous".

    Thanks,

    tglx


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