From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ch1outboundpool.messaging.microsoft.com (ch1ehsobe001.messaging.microsoft.com [216.32.181.181]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (Client CN "mail.global.frontbridge.com", Issuer "Microsoft Secure Server Authority" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 640912C007E for ; Wed, 11 Jul 2012 10:41:27 +1000 (EST) Message-ID: <4FFCCBAD.40504@freescale.com> Date: Tue, 10 Jul 2012 19:41:17 -0500 From: Scott Wood MIME-Version: 1.0 To: Benjamin Herrenschmidt Subject: Re: [PATCH] powerpc/booke: Eliminate rfi from exception entry path. References: <20120711003454.GA22757@tyr.buserror.net> <1341967010.18850.19.camel@pasglop> In-Reply-To: <1341967010.18850.19.camel@pasglop> Content-Type: text/plain; charset="UTF-8" Cc: linuxppc-dev@lists.ozlabs.org, Alexander Graf , Stuart Yoder List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 07/10/2012 07:36 PM, Benjamin Herrenschmidt wrote: > On Tue, 2012-07-10 at 19:34 -0500, Scott Wood wrote: >> Unlike classic, we don't really need the MSR change to be atomic with the >> branch. This eliminates a trap as a KVM guest (in the absence of >> hardware hypervisor extensions), where mtmsr is paravirtualized but rfi >> is not. For a virtualized guest without any paravirtualization, this >> eliminates an additional two traps (SRR0/1). > > In fact, I wonder, what do we write into the MSR at this point that > wasn't already in it in BookE ? RI ? I wonder if we could get away > without the mtmsr alltogether... Doesn't EE get set there for some exceptions? -Scott