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From: Rusty Russell <rusty@rustcorp.com.au>
To: Ingo Molnar <mingo@elte.hu>
Cc: "Ahmed S. Darwish" <darwish.07@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	LKML <linux-kernel@vger.kernel.org>,
	lguest@ozlabs.org, akpm <akpm@linux-foundation.org>,
	Jeremy Fitzhardinge <jeremy@xensource.com>
Subject: Re: [BUG + PATCH/Bugfix] x86/lguest: fix pgdir pmd index calculation
Date: Tue, 4 Mar 2008 17:37:24 +1100
Message-ID: <200803041737.24988.rusty@rustcorp.com.au> (raw)
In-Reply-To: <20080229195838.GB21494@elte.hu>

On Saturday 01 March 2008 06:58:38 Ingo Molnar wrote:
> * Ahmed S. Darwish <darwish.07@gmail.com> 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.
>
> 	Ingo

It does (assuming host support), but when I tried to use the normal TSC code 
it poked at other things which a guest couldn't do.

Currently I've hit another issue, but revisiting this is on my TODO.  The 
cpu_has_tsc panic is overzealous, since we deal without it, but it'd be nice 
to use the common TSC clock code.

Thanks,
Rusty.

  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 [this message]
2008-03-04 12:06           ` Rusty Russell
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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