linux-kernel - Re: [PATCH] Skip tsc synchronization checks if CONSTANT

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Message-ID: <20081022221316.GW12825@one.firstfloor.org>
Date:	Thu, 23 Oct 2008 00:13:16 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Alok Kataria <akataria@...are.com>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Daniel Hecht <dhecht@...are.com>
Subject: Re: [PATCH] Skip tsc synchronization checks if CONSTANT_TSC bit is set.

> > Adding it with vmware detection code is not useful.
> 
> The VMware detection code is something that's needed anyways for other
> purposes(getting tsc_freq right now). So the code which force sets this
> TSC_CONSTANT bit is trivial.

It would be better to eliminate that too. Why do you need it anyways?

> Apart from that, as i said yesterday, this should be viewed as a special
> case for VMware products which don't already set this bit. Changing the
> behavior for already existing products is not feasible.

On old hypervisors Linux already runs fine without TSC, doesn't it?

-Andi
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