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Date:	Sat, 1 Feb 2014 09:10:51 -0800
From:	Andy Lutomirski <>
To:	Clemens Ladisch <>
Cc:	X86 ML <>,
	"" <>
Subject: Re: [PATCH] x86: Remove hpet vclock support

On Sat, Feb 1, 2014 at 7:43 AM, Clemens Ladisch <> wrote:
> Andy Lutomirski wrote:
>> The HPET is so amazingly slow that this is barely a win.
> What happens on CPUs where the TSC cannot be used for the clock?

vclock_gettime, etc will fall back to using syscalls, just like they
would on systems using the PIT timer.

>> it scares me a tiny bit to map a piece of crappy hardware where every
>> userspace program can poke at it (even if said poking is read-only).
>> Let's just remove it.
> So this mapping is a backdoor to bypass the restrictions on /dev/hpet?  ;-)

Yes, except that it's read-only.

At some point, someone will probably want to run code in a sandbox
that can't tell time at all.  That will be messy, but this is a decent
first little step.

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