From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH] x86emul: support clzero Date: Wed, 23 Sep 2015 18:37:31 +0100 Message-ID: <5602E35B.4060704@citrix.com> References: <56016E8102000078000A45B7@prv-mh.provo.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1ZenzU-0006Ui-Ib for xen-devel@lists.xenproject.org; Wed, 23 Sep 2015 17:38:00 +0000 In-Reply-To: <56016E8102000078000A45B7@prv-mh.provo.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich , xen-devel Cc: Keir Fraser , Aravind Gopalakrishnan , suravee.suthikulpanit@amd.com List-Id: xen-devel@lists.xenproject.org On 22/09/15 14:06, Jan Beulich wrote: > ... in anticipation of this possibly going to get used by guests for > basic thinks like memset() or clearing or pages. > > Since the emulation doesn't use clzero itself, checking the guest's > CPUID for the feature to be exposed is (intentionally) being avoided > here. All that's required is sensible guest side data for the clflush > line size. > > Signed-off-by: Jan Beulich Where have you found this instruction? Googling, I have found a presentation talking about it being new in the new AMD Zen cores, but I still can't locate any technical documentation on the matter. ~Andrew