From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Thu, 11 Mar 2010 04:42:04 +0100 (CET) Received: from mail-ew0-f224.google.com ([209.85.219.224]:34393 "EHLO mail-ew0-f224.google.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S1492047Ab0CKDmA (ORCPT ); Thu, 11 Mar 2010 04:42:00 +0100 Received: by ewy24 with SMTP id 24so1849553ewy.27 for ; Wed, 10 Mar 2010 19:41:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:subject:from:reply-to:to:cc :in-reply-to:references:content-type:organization:date:message-id :mime-version:x-mailer:content-transfer-encoding; bh=/QwW/Sik4jBsqpPDDxfJPhsLwABrgYfVu9jhw/o9j6Q=; b=WHd6v6xNZYzPdCgbYETsoQMghJMpmaNyiBx8PQ3cNy4IZFi2NnCwJdP5qX34C/VDNP jxLjY93WobhwjhVhAYJO09IdHeaH5Stz2w9udUcPFQ/dJjAdUhR/CI/c712fV7W5AwOk 5t7+rw6ER4L7U0ThzZlLq0y34tKSlKbRfkm24= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:reply-to:to:cc:in-reply-to:references:content-type :organization:date:message-id:mime-version:x-mailer :content-transfer-encoding; b=qg1y9Qo1ZE+qSEb57dOD2ibzqxCAqqbZej6XAzLCatyrY+LjcBDciAPlWf+zkJVNSn 6wHYXXpiD14t2VNJM4zTLGBEw1agBgXz+BZHPCIRAlXIDHPQI9yranhsf8ItGBy82Ts6 fe3Z4dl4wCLa4hDPIg+nrvgs+Hg6g9KAmmtmM= Received: by 10.213.100.165 with SMTP id y37mr5754300ebn.71.1268278914418; Wed, 10 Mar 2010 19:41:54 -0800 (PST) Received: from [202.201.12.142] ([202.201.12.142]) by mx.google.com with ESMTPS id 16sm4430477ewy.7.2010.03.10.19.41.47 (version=TLSv1/SSLv3 cipher=RC4-MD5); Wed, 10 Mar 2010 19:41:52 -0800 (PST) Subject: Re: [PATCH 1/3] Loongson-2F: Flush the branch target history such as BTB and RAS From: Wu Zhangjin Reply-To: wuzhangjin@gmail.com To: Shinya Kuribayashi Cc: Ralf Baechle , Greg KH , linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, zhangfx , yanh In-Reply-To: <4B98632E.70806@necel.com> References: <4B98632E.70806@necel.com> Content-Type: text/plain; charset="UTF-8" Organization: DSLab, Lanzhou University, China Date: Thu, 11 Mar 2010 11:35:20 +0800 Message-ID: <1268278520.17798.5.camel@falcon> Mime-Version: 1.0 X-Mailer: Evolution 2.28.2 Content-Transfer-Encoding: 8bit Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 26196 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: wuzhangjin@gmail.com Precedence: bulk X-list: linux-mips On Thu, 2010-03-11 at 12:27 +0900, Shinya Kuribayashi wrote: > Wu Zhangjin wrote: > > From: Wu Zhangjin > > > > As the Chapter 15: "Errata: Issue of Out-of-order in loongson"[1] shows, to > > workaround the Issue of Loongson-2F，We need to do: > > > > "When switching from user model to kernel model, you should flush the branch > > target history such as BTB and RAS." > > Just wondered, model or mode? > Hmm, should be mode. > > This patch did clear BTB(branch target buffer), forbid RAS(row address strobe) > > via Loongson-2F's 64bit diagnostic register. > > Are you sure that RAS represents "Row Address Strobe", not "Return > Address Stack?" > Hi, Yanhua(from Lemote), can you help to clear this part? > By the way, we have a similar local workaround for vr55xx processors > when switching from kernel mode to user mode. It's not necessarily > related to out-of-order issues, but we need to prevent the processor > from doing instruction prefetch beyond "eret" instruction. > > In the long term, it would be appreciated that the kernel has a set > of hooks when switching KUX-modes, so that each machine could have > his own, processor-specific treatmens. > Good idea. Thanks! Regards, Wu Zhangjin