From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Chen, Kenneth W" Date: Fri, 03 Jun 2005 19:26:47 +0000 Subject: RE: Initialization of cr.dcr Message-Id: <200506031926.j53JQkg31275@unix-os.sc.intel.com> List-Id: References: <42A01CA2.8010209@hob.de> In-Reply-To: <42A01CA2.8010209@hob.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org David Mosberger wrote on Friday, June 03, 2005 12:11 PM > >>> On Fri, 3 Jun 2005 13:27:54 -0500 (CDT), Russ Anderson said: > > Russ> Ken Chen wrote: > >> Christian Hildner wrote on Friday, June 03, 2005 2:02 AM > > >> playing around with speculation I found that on initialization > >> dcr.dm is > not set, while the comment says "Initialize default > >> control register to > defer all speculative faults". To be > >> conform to the comment (and also to > the expected behavior) the > >> value IA64_DCR_DM should be added in > arch/ia64/kernel/setup.c. > > >> It should be the other way around: update the comments to reflect > >> what the code does. Turning off dcr.dm is a big win for > >> speculative load where you do want the tlb miss to be serviced up > >> front. > > That's correct. We changed this a long time ago and apparently forgot > to update the comment. Patch to update the comments to reflect the actual code in cpu_init(). Signed-off-by: Ken Chen Acked-by: David Mosberger-Tang --- linux-2.6.11/arch/ia64/kernel/setup.c.orig 2005-06-03 12:21:00.891940166 -0700 +++ linux-2.6.11/arch/ia64/kernel/setup.c 2005-06-03 12:22:36.036470251 -0700 @@ -720,7 +720,7 @@ cpu_init (void) ia64_set_kr(IA64_KR_PT_BASE, __pa(ia64_imva(empty_zero_page))); /* - * Initialize default control register to defer all speculative faults. The + * Initialize default control register not to defer speculative faults. The * kernel MUST NOT depend on a particular setting of these bits (in other words, * the kernel must have recovery code for all speculative accesses). Turn on * dcr.lc as per recommendation by the architecture team. Most IA-32 apps