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From: Rusty Russell <>
To: Ingo Molnar <>
Cc: "Ahmed S. Darwish" <>,
	Thomas Gleixner <>,
	Ingo Molnar <>, "H. Peter Anvin" <>,
	LKML <>,, akpm <>,
	Jeremy Fitzhardinge <>
Subject: Re: [BUG + PATCH/Bugfix] x86/lguest: fix pgdir pmd index calculation
Date: Tue, 4 Mar 2008 23:06:57 +1100
Message-ID: <> (raw)
In-Reply-To: <>

On Saturday 01 March 2008 06:58:38 Ingo Molnar wrote:
> * Ahmed S. Darwish <> wrote:
> > On the lguest _guest_ side, 'cpu_has_tsc' is _always_ false (due to
> > lguest using his own clocksource ?), thus a guest with a pentium+ cpu
> > always panics with:
> does the "RDTSC" instruction work in an lguest guest? If not, then the
> lguest kernel is correct in not exposing it - and then the solution is
> to build a non-TSC guest kernel. Does the patch below help?
> but if the RDTSC instruction does work in an lguest guest, then the
> proper approach would be to expose it in the CPU features.

Yes, and after some investigation, I came up with two patches.  I'll queue 
both to you if that's ok, since they're dependent.

When lguest was being developed we didn't have a get_tsc_khz hook, so I had to 
kill the TSC cpuid bit.  Nowdays, the code can actually be much more natural: 
the Host tells us the cpu khz, and if it's zero, we fall back to the 
dumb "lguest" clock.


  parent reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-24 15:55 Ahmed S. Darwish
2008-02-24 16:18 ` Ingo Molnar
2008-02-24 16:26   ` Ahmed S. Darwish
2008-02-25  0:18     ` Ahmed S. Darwish
2008-02-29  0:32       ` Ahmed S. Darwish
2008-02-29 19:58         ` Ingo Molnar
2008-03-04  6:37           ` Rusty Russell
2008-03-04 12:06           ` Rusty Russell [this message]
2008-03-04 12:07           ` [PATCH 1/2] x86: If we cannot calibrate the TSC, we panic Rusty Russell
2008-03-04 12:11             ` [PATCH 2/2] lguest: sanitize the clock Rusty Russell
2008-03-04 12:55 ` [BUG + PATCH/Bugfix] x86/lguest: fix pgdir pmd index calculation Rusty Russell
2008-03-04 15:11   ` Ahmed S. Darwish

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