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    SubjectRe: [PATCH] x86: Export tsc related information in sysfs
    On 05/18/2010 01:29 PM, Dan Magenheimer wrote:
    >
    > Yes, understood, a minor semantic issue. From a kernel perspective
    > vsyscalls are kernelspace, so IIUC this is OK with tglx/etc.
    >
    > Since vsyscall shouldn't be using rdtsc when the kernel
    > doesn't trust TSC, it doesn't matter if CR4.TSD is enabled when
    > the kernel doesn't trust TSC.
    >

    That is correct.

    > I'm still not sure if you are in favor of optionally emulating
    > PL3 rdtsc instructions or not? I thought my proposal was
    > just filling out some details of your proposal and suggesting
    > a default.

    I'm not in favor of emulating rdtsc instructions. I would consider
    letting them SIGILL (actually SIGSEGV since RDTSC #GP in userspace) when
    the TSC is unavailable, though.

    It's not clear to me that it's possible, though, since that also affects
    RDTSCP.

    -hpa




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