From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22584C433F5 for ; Fri, 22 Oct 2021 16:23:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DCAEB6112F for ; Fri, 22 Oct 2021 16:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233206AbhJVQZq (ORCPT ); Fri, 22 Oct 2021 12:25:46 -0400 Received: from foss.arm.com ([217.140.110.172]:56442 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229968AbhJVQZp (ORCPT ); Fri, 22 Oct 2021 12:25:45 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4D4981FB; Fri, 22 Oct 2021 09:23:27 -0700 (PDT) Received: from [10.57.27.181] (unknown [10.57.27.181]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 120843F73D; Fri, 22 Oct 2021 09:23:24 -0700 (PDT) Subject: Re: [RFCv1 4/4] perf: arm_spe: Dynamically switch PID tracing to contextidr From: James Clark To: Leo Yan References: <20211021134530.206216-1-leo.yan@linaro.org> <20211021134530.206216-5-leo.yan@linaro.org> <854fb1a2-e5f1-f237-685f-8ddb0557c98b@arm.com> Cc: Catalin Marinas , Will Deacon , Mark Rutland , Kees Cook , Ard Biesheuvel , Sami Tolvanen , Nicholas Piggin , James Morse , Marc Zyngier , Joey Gouly , Peter Collingbourne , Vincenzo Frascino , "Peter Zijlstra (Intel)" , Stephane Eranian , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Message-ID: <0a53529a-576c-05b0-4fe5-906195faf243@arm.com> Date: Fri, 22 Oct 2021 17:23:23 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <854fb1a2-e5f1-f237-685f-8ddb0557c98b@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/10/2021 16:36, James Clark wrote: > > > On 21/10/2021 14:45, Leo Yan wrote: >> Now Arm64 provides API for enabling and disable PID tracing, Arm SPE >> driver invokes these functions to dynamically enable it during >> profiling when the program runs in root PID name space, and disable PID >> tracing when the perf event is stopped. >> >> Device drivers should not depend on CONFIG_PID_IN_CONTEXTIDR for PID >> tracing, so this patch uses the consistent condition for setting bit >> EL1_CX for PMSCR. > > Hi Leo, > > I've been testing this change, but I'm seeing something strange. Not sure > if it's a problem on my side or not yet. With this command: > > sudo ./perf record -vvv -e arm_spe//u -- taskset --cpu-list 1 bash -c ls > > I'm only seeing 0 values for context: > > sudo ./perf report -D | grep CONTEXT > > . 00038dce: 65 00 00 00 00 CONTEXT 0x0 el2 > . 00038e0e: 65 00 00 00 00 CONTEXT 0x0 el2 > > I added a printk to the function, and I see it print non zero values, although > there are some zero ones mixed in there too: > > diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h > index 0c1669db19a1..8f0fb43a5fac 100644 > --- a/arch/arm64/include/asm/mmu_context.h > +++ b/arch/arm64/include/asm/mmu_context.h > @@ -33,7 +33,8 @@ static inline void contextidr_thread_switch(struct task_struct *next) > if (!static_branch_unlikely(&contextidr_in_use)) > return; > > - write_sysreg(task_pid_nr(next), contextidr_el1); > + printk("Set %d\n", task_pid_nr(next)); > + write_sysreg(task_pid_nr(next), contextidr_el2); > isb(); > } > > > Results in this: > > [ 53.257905] Set 77 > [ 53.257909] Set 0 > [ 53.258180] Set 77 > [ 53.258183] Set 0 > [ 53.258385] Set 309 > [ 53.258385] Set 172 > [ 53.258425] Set 77 > [ 53.258443] Set 990 > [ 53.258449] Set 77 > [ 53.258455] Set 990 > [ 53.258467] Set 310 > [ 53.258719] Set 7 > [ 53.258728] Set 77 > [ 53.258731] Set 0 > [ 53.258733] Set 0 > [ 53.258738] Set 7 > > > Without your patchset I don't get 0 values in the SPE trace anymore: > > . 0000050e: 65 b1 01 00 00 CONTEXT 0x1b1 el2 > . 0000054e: 65 b1 01 00 00 CONTEXT 0x1b1 el2 > . 0000058e: 65 ac 01 00 00 CONTEXT 0x1ac el2 > . 000005ce: 65 ac 01 00 00 CONTEXT 0x1ac el2 > Is it an issue with building with CONTEXTIDR disabled? Seems like this change results in context packets set to 0 when it's disabled rather than having the packets disabled like they used to be: zcat /proc/config.gz | grep CONTEXTIDR # CONFIG_PID_IN_CONTEXTIDR is not set sudo ./perf report -D | grep CONTEXT . 00045b4e: 65 00 00 00 00 CONTEXT 0x0 el2 When I build with CONFIG_PID_IN_CONTEXTIDR=y the contexts are non zero so it seems to be working that way. But ./perf record -e arm_spe//u -a does have context IDs even when CONFIG_PID_IN_CONTEXTIDR=n. So I'm still a bit confused.