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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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