This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] [PATCH] X86: cpuid faulting feature enable

To: Jan Beulich <JBeulich@xxxxxxxxxx>, Jinsong Liu <jinsong.liu@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] X86: cpuid faulting feature enable
From: Keir Fraser <keir.xen@xxxxxxxxx>
Date: Fri, 01 Jul 2011 17:07:52 +0100
Cc: Kevin Tian <kevin.tian@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Haitao Shan <haitao.shan@xxxxxxxxx>, Xin Li <xin.li@xxxxxxxxx>
Delivery-date: Fri, 01 Jul 2011 09:09:04 -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=nPIehP0W7f7tetmt76oID38A8j7cm3YT9zk4QCKv8rE=; b=uHWdMDULSIbX5ouJ7MQ1hjg9sbFeLpLU325XlQdyLfczrI6FeyY3Koj7f2cSjWgv4r a8sHbFWUhZ+U8DkD+pEjPEF4Mv882bktbfi3FpHcVCrMGGKN0+elzCO3DuymqIS2SyzE a5Defx0aFhXhEuecQKNe+gLQo22NhGS3dSDo8=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4E0E088A020000780004BB07@xxxxxxxxxxxxxxxxxxxx>
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: Acw4CQeVZMnHpMVFU0iR1jrN1b1wSA==
Thread-topic: [Xen-devel] [PATCH] X86: cpuid faulting feature enable
User-agent: Microsoft-Entourage/
On 01/07/2011 16:48, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>> + if ( cpuid_faulting_flip )
>> + {
>> +  unsigned int enable;
>> +
>> +  enable = !is_hvm_vcpu(next) && (next->domain->domain_id != 0);
> Excluding Dom0 here is perhaps questionable (as it could allow hiding
> features not supported by Xen from applications).

It's probably because of a need for raw cpuid in libxc/xc_cpuid_x86.c where
we need to detect things like long mode. We could do that another way, or
provide a new paravirtualised raw cpuid just for dom0.

Not a barrier to this patch going in imo.

I suppose HVM VCPUs are excluded because otherwise the new feature would be
unexpectedly enabled in non-root mode too, and make HVM guests crash? :-)

 -- Keir

Xen-devel mailing list