From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH v6 05/10] Clear AC bit in RFLAGS to protect Xen itself by SMAP Date: Wed, 7 May 2014 12:53:40 +0100 Message-ID: <536A1EC4.40304@citrix.com> References: <1399450782-14735-1-git-send-email-feng.wu@intel.com> <1399450782-14735-6-git-send-email-feng.wu@intel.com> <536A009B.20802@citrix.com> <536A37DD020000780000FE3D@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <536A37DD020000780000FE3D@mail.emea.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 Cc: kevin.tian@intel.com, Feng Wu , ian.campbell@citrix.com, eddie.dong@intel.com, xen-devel@lists.xen.org, jun.nakajima@intel.com List-Id: xen-devel@lists.xenproject.org On 07/05/14 12:40, Jan Beulich wrote: >>>> On 07.05.14 at 11:44, wrote: >> On 07/05/14 09:19, Feng Wu wrote: >>> @@ -673,6 +675,7 @@ ENTRY(nmi_crash) >>> ud2 >>> >>> ENTRY(machine_check) >>> + ASM_CLAC >> This is not needed. the start of handle_ist_exception has a SAVE_ALL, >> which also covers the nmi entry point. >> >> On the subject of IST exceptions, perhaps the double fault explicitly >> wants a STAC to reduce the likelihood of taking a further fault while >> trying to dump state. ? > I agree. And perhaps along with do_double_fault(), fatal_trap() > should then also get a stac() added? > > Jan > With doubt_fault: being sole caller of do_double_fault(), editing the entry point in entry.S to "ASM_STAC; SAVE_ALL 0" is sufficient to avoid stac() in do_doube_fault() itself. I would agree that fatal_trap() wants an stac() in it. ~Andrew