From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 404lby6W2JzF1bM for ; Tue, 20 Mar 2018 05:54:38 +1100 (AEDT) Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w2JIsKmS076286 for ; Mon, 19 Mar 2018 14:54:36 -0400 Received: from e06smtp15.uk.ibm.com (e06smtp15.uk.ibm.com [195.75.94.111]) by mx0a-001b2d01.pphosted.com with ESMTP id 2gtgq3nqqk-1 (version=TLSv1.2 cipher=AES256-SHA256 bits=256 verify=NOT) for ; Mon, 19 Mar 2018 14:54:36 -0400 Received: from localhost by e06smtp15.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 19 Mar 2018 18:54:34 -0000 Date: Tue, 20 Mar 2018 00:24:27 +0530 From: "Naveen N. Rao" Subject: Re: [PATCH 1/2] powerpc64/ftrace: Add a field in paca to disable ftrace in unsafe code paths To: Steven Rostedt Cc: Anton Blanchard , Benjamin Herrenschmidt , linuxppc-dev@lists.ozlabs.org, Michael Ellerman , Nicholas Piggin , Paul Mackerras , sathnaga@linux.vnet.ibm.com References: <20180319101344.72144f30@gandalf.local.home> In-Reply-To: <20180319101344.72144f30@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Message-Id: <1521485608.a0kau5nu5z.naveen@linux.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Steven Rostedt wrote: > On Mon, 19 Mar 2018 14:43:00 +0530 > "Naveen N. Rao" wrote: >=20 >> diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S b/arch/power= pc/kernel/trace/ftrace_64_mprofile.S >> index 3f3e81852422..fdf702b4df25 100644 >> --- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S >> +++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S >> @@ -60,6 +60,19 @@ _GLOBAL(ftrace_caller) >> mfxer r10 >> mfcr r11 >> =20 >> +#ifdef CONFIG_KVM >> + lbz r3, PACA_FTRACE_DISABLED(r13) >> + cmpdi r3, 0 >> + beq 1f >> + mflr r3 >> + mtctr r3 >> + REST_GPR(3, r1) >> + addi r1, r1, SWITCH_FRAME_SIZE >> + mtlr r0 >> + bctr >> +1: >> +#endif >=20 > I wonder if we should try to move the return out of the fast path (for > cache reasons), as most of the time the above compare will be true. That > is: >=20 > #ifdef CONFIG_KVM > lbz r3, PACA_FTRACE_DISABLED(r13) > cmpdi r3, 0 > bne no_trace > #endif >=20 > /* rest of ftrace_caller code */ >=20 > /* after ftrace_caller... */ > bctr /* jump after _mcount site */ >=20 > #ifdef CONFIG_KVM > no_trace: > mflr r3 > mtctr r3 > REST_GPR(3, r1) > addi r1, r1, SWITCH_FRAME_SIZE > mtlr r0 > bctr > #endif Thanks, I'll incorporate those changes in my next version. - Naveen =