linux-kernel - Re: [PATCH 0/3] Improve TSC as a clocksource under VMware

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Message-ID: <20081021183634.GA1475@ucw.cz>
Date:	Tue, 21 Oct 2008 20:36:34 +0200
From:	Pavel Machek <pavel@...e.cz>
To:	Alok Kataria <akataria@...are.com>
Cc:	"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 0/3] Improve TSC as a clocksource under VMware

On Tue 2008-10-21 09:48:08, Alok Kataria wrote:
> On Tue, 2008-10-21 at 02:50 -0700, Pavel Machek wrote:
> > > Hi,
> > >
> > > This patch set makes some changes to the TSC code, so that it is always
> > > used as the default clocksource when running under VMware.
> > > The first 2 patches do the ground work of adding code to detect if we
> > > are running under VMware.
> > > The third patch adds a tsc_reliable flag which tells us that TSC is
> > > reliable on this system, so that we can skip some tests which can
> > > potentially mark TSC as unstable. Details under individual patch
> > > headers.
> > 
> > How do you _know_ TSC is stable under VMWare? 
> 
> Since we implement it that way :)
> The hypervisor takes care of providing a constant rate TSC to the guest
> on such systems which have variable frequency.

Aha, so tsc accesses trap to VMWare? Ok, then...

-- 
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