[Xen-devel] Re: expose MWAIT to dom0

To:	"Tian, Kevin" <kevin.tian@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject:	[Xen-devel] Re: expose MWAIT to dom0
From:	Keir Fraser <keir.xen@xxxxxxxxx>
Date:	Mon, 15 Aug 2011 08:44:41 +0100
Cc:	"Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>, "'Keir Fraser \(keir@xxxxxxx\)'" <keir@xxxxxxx>, "Wei, Gang" <gang.wei@xxxxxxxxx>
Delivery-date:	Mon, 15 Aug 2011 00:45:22 -0700
Dkim-signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=user-agent:date:subject:from:to:cc:message-id:thread-topic :thread-index:in-reply-to:mime-version:content-type :content-transfer-encoding; bh=Gi25v7p49Z1FQ9zrFuQMAOzw5qG2pDuo3ogKskkEcj0=; b=mOPW6GzTjw6UzwZq8mE9xPkFjVxjaN/dOLh3mTEDQujJziY9MT6bDOb1a0Db/QKFVz 8fWRyc18k9qEfe7CYeBilVuCIhMz5nj49KULpSLg/+fe7rhVdDWEQd3+Zhk6j1SJoyTH kpg7ozvdhmBsQRtAHwlGwjX5uonzCGddniiWo=
Envelope-to:	www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to:	<625BA99ED14B2D499DC4E29D8138F15062D2E80D67@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
List-help:	<mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id:	Xen developer discussion <xen-devel.lists.xensource.com>
List-post:	<mailto:xen-devel@lists.xensource.com>
List-subscribe:	<http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe:	<http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender:	xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index:	Acxa+ymibBfDa2PpTRKdAF4mJFeEFAAHRLo3AACWc5AAASamtg==
Thread-topic:	expose MWAIT to dom0
User-agent:	Microsoft-Entourage/12.30.0.110427

On 15/08/2011 08:13, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

>> Well the problem is some older kernels will try to use MWAIT if they see the
>> feature in CPUID. Of course that doesn't work outside ring 0.
>> 
> 
> if those old kernels are still of interest, then possibly a boot option in Xen
> would
> be applausive. Or can we just allow selectively exposing MWAIT when xen
> cpuidle is enabled?

The kernel could unconditionally advertise MWAIT from its cpuid pv_ops hook?
If all that's doing is causing relevant parts of BIOS tables to be parsed,
would that be safe when MWAIT is not in fact available?

Else the kernel could get the flag from the real non paravirtualised CPUID
instruction.

 -- Keir

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

WARNING - OLD ARCHIVES

xen-devel

[Xen-devel] Re: expose MWAIT to dom0