From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from am1outboundpool.messaging.microsoft.com (am1ehsobe003.messaging.microsoft.com [213.199.154.206]) (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 8B8272C007E for ; Wed, 11 Jul 2012 10:35:20 +1000 (EST) Date: Tue, 10 Jul 2012 19:34:54 -0500 From: Scott Wood To: Benjamin Herrenschmidt Subject: [PATCH] powerpc/booke: Eliminate rfi from exception entry path. Message-ID: <20120711003454.GA22757@tyr.buserror.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" 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: , 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). Signed-off-by: Scott Wood --- arch/powerpc/kernel/entry_32.S | 16 ++++++++++++++++ 1 files changed, 16 insertions(+), 0 deletions(-) diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S index ba3aeb4..6bb637c 100644 --- a/arch/powerpc/kernel/entry_32.S +++ b/arch/powerpc/kernel/entry_32.S @@ -193,6 +193,9 @@ transfer_to_handler_cont: lwz r11,0(r9) /* virtual address of handler */ lwz r9,4(r9) /* where to go when done */ #ifdef CONFIG_TRACE_IRQFLAGS +#ifdef CONFIG_BOOKE + mtmsr r10 +#else lis r12,reenable_mmu@h ori r12,r12,reenable_mmu@l mtspr SPRN_SRR0,r12 @@ -201,6 +204,7 @@ transfer_to_handler_cont: RFI reenable_mmu: /* re-enable mmu so we can */ mfmsr r10 +#endif /* !CONFIG_BOOKE */ lwz r12,_MSR(r1) xor r10,r10,r12 andi. r10,r10,MSR_EE /* Did EE change? */ @@ -247,11 +251,23 @@ reenable_mmu: /* re-enable mmu so we can */ mtlr r9 bctr /* jump to handler */ #else /* CONFIG_TRACE_IRQFLAGS */ +#ifdef CONFIG_BOOKE + /* + * We're not changing address space on Book E, and the extra rfi + * can hurt when virtualized without hardware support -- whereas + * mtmsr can be paravirtualized. + */ + mtmsr r10 + mtctr r11 + mtlr r9 + bctr +#else mtspr SPRN_SRR0,r11 mtspr SPRN_SRR1,r10 mtlr r9 SYNC RFI /* jump to handler, enable MMU */ +#endif /* !CONFIG_BOOKE */ #endif /* CONFIG_TRACE_IRQFLAGS */ #if defined (CONFIG_6xx) || defined(CONFIG_E500) -- 1.7.5.4