From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Ostrovsky Subject: Re: [Xen-devel] [PATCH v2 3/3] paravirt: rename paravirt_enabled to paravirt_legacy Date: Mon, 8 Feb 2016 11:52:51 -0500 Message-ID: <56B8C7E3.5060706@oracle.com> References: <20160206220437.GA4435@pd.tnic> <56B8B6BF.6030007@oracle.com> <20160208155507.GF28980@pd.tnic> <56B8BCDB.9040701@citrix.com> <56B8BE58.6070003@oracle.com> <56B8C1BC.9040603@citrix.com> <56B8C2C8.8050406@oracle.com> <20160208163526.GI28980@pd.tnic> <56B8C490.1060004@citrix.com> <20160208164545.GJ28980@pd.tnic> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160208164545.GJ28980@pd.tnic> Sender: linux-kernel-owner@vger.kernel.org To: Borislav Petkov , Andrew Cooper Cc: X86 ML , david.e.box@intel.com, Andrey Ryabinin , Lv Zheng , Jan Beulich , "H. Peter Anvin" , qiuxishi@huawei.com, cocci@systeme.lip6.fr, Xen Devel , Joerg Roedel , "Rafael J. Wysocki" , Robert Moore , Ingo Molnar , Andrey Ryabinin , Mauro Carvalho Chehab , "Luis R. Rodriguez" , Rusty Russell , Thomas Gleixner , mcb30@ipxe.org, Juergen Gross , "linux-kernel@vger.kernel.org" , Andy Lutomirski , "Luis R. Rodriguez" , long.wanglong@huawei.com, Fengguang Wu List-Id: xen-devel@lists.xenproject.org On 02/08/2016 11:45 AM, Borislav Petkov wrote: > On Mon, Feb 08, 2016 at 04:38:40PM +0000, Andrew Cooper wrote: >> Does the early loader have extable support? If so, this is fairly easy >> to fix. If not, we have a problem. > It doesn't and regardless, you want to have this CPUID querying as > simple as possible. No special handling, no special prefixes as it > should be able to run on other hypervisors too. > > If one can't execute a simple CPUID(0x4...) on a xen guest and get the > results back, then for early, we will have to do what we've done until > now and simply emulate the MSR accesses. I think xen_hypervisor check can be done in microcode_init() as this is first time PV kernel deals with microcode. Let me try it --- I want to see what happens on hotplug and resume but I am reasonably certain this should work during boot. -boris > > Later code can use then xen_cpuid() and all is fine. We should still get > rid of paravirt_enabled() though. >