From mboxrd@z Thu Jan  1 00:00:00 1970
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH v2 2/3] x86/AMD: support further feature
 masking MSRs
Date: Mon, 07 Apr 2014 11:21:48 -0400
Message-ID: <5342C28C.2090809@oracle.com>
References: <53428DCC020000780000607D@nat28.tlf.novell.com>
	<53428F4402000078000060BB@nat28.tlf.novell.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; Format="flowed"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Received: from mail6.bemta5.messagelabs.com ([195.245.231.135])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <boris.ostrovsky@oracle.com>) id 1WXBJx-00036Z-R6
	for xen-devel@lists.xenproject.org; Mon, 07 Apr 2014 15:18:51 +0000
In-Reply-To: <53428F4402000078000060BB@nat28.tlf.novell.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Jan Beulich <JBeulich@suse.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>, Keir Fraser <keir@xen.org>, Aravind Gopalakrishnan <aravind.gopalakrishnan@amd.com>, suravee.suthikulpanit@amd.com
List-Id: xen-devel@lists.xenproject.org

On 04/07/2014 05:43 AM, Jan Beulich wrote:

@@ -179,11 +196,39 @@ static void __devinit set_cpuidmask(cons
  	printk("Writing CPUID extended feature mask ECX:EDX -> %08Xh:%08Xh\n",
  	       extfeat_ecx, extfeat_edx);
  
+	if (c->cpuid_level >= 7)
+		cpuid_count(7, 0, &eax, &ebx, &ecx, &edx);
+	else
+		ebx = eax = 0;
+	if ((eax | ebx) && ~(l7s0_eax & l7s0_ebx)) {
+		if (l7s0_eax > eax)
+			l7s0_eax = eax;
+		l7s0_ebx &= ebx;


Can you explain why eax is treated differently here (i.e. not ANDing it 
as is done with ebx)?

-boris