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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DBC8BC31E48 for ; Wed, 12 Jun 2019 12:48:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BCACB208C2 for ; Wed, 12 Jun 2019 12:48:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2439207AbfFLMsK (ORCPT ); Wed, 12 Jun 2019 08:48:10 -0400 Received: from foss.arm.com ([217.140.110.172]:52646 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2439208AbfFLMsK (ORCPT ); Wed, 12 Jun 2019 08:48:10 -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 80036337; Wed, 12 Jun 2019 05:48:09 -0700 (PDT) Received: from [10.1.196.105] (eglon.cambridge.arm.com [10.1.196.105]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 39D8E3F246; Wed, 12 Jun 2019 05:48:07 -0700 (PDT) Subject: Re: [PATCH v1 1/5] KVM: arm/arm64: Remove kvm_mmio_emulate tracepoint To: Zenghui Yu Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, marc.zyngier@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, acme@kernel.org, linuxarm@huawei.com, acme@redhat.com, peterz@infradead.org, alexander.shishkin@linux.intel.com, mingo@redhat.com, ganapatrao.kulkarni@cavium.com, namhyung@kernel.org, jolsa@redhat.com, xiexiangyou@huawei.com References: <1560330526-15468-1-git-send-email-yuzenghui@huawei.com> <1560330526-15468-2-git-send-email-yuzenghui@huawei.com> From: James Morse Message-ID: Date: Wed, 12 Jun 2019 13:48:05 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <1560330526-15468-2-git-send-email-yuzenghui@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi, On 12/06/2019 10:08, Zenghui Yu wrote: > In current KVM/ARM code, no one will invoke trace_kvm_mmio_emulate(). > Remove this TRACE_EVENT definition. Oooer. We can't just go removing these things, they are visible to user-space. I recall an article on this: https://lwn.net/Articles/737530/ "Another attempt to address the tracepoint ABI problem" I agree this is orphaned, it was added by commit 45e96ea6b369 ("KVM: ARM: Handle I/O aborts"), but there never was a caller. The problem with removing it is /sys/kernel/debug/tracing/events/kvm/kvm_mmio_emulate disappears. Any program relying on that being present (but useless) is now broken. Thanks, James > diff --git a/virt/kvm/arm/trace.h b/virt/kvm/arm/trace.h > index 204d210..8b7dff2 100644 > --- a/virt/kvm/arm/trace.h > +++ b/virt/kvm/arm/trace.h > @@ -114,27 +114,6 @@ > __entry->type, __entry->vcpu_idx, __entry->irq_num, __entry->level) > ); > > -TRACE_EVENT(kvm_mmio_emulate, > - TP_PROTO(unsigned long vcpu_pc, unsigned long instr, > - unsigned long cpsr), > - TP_ARGS(vcpu_pc, instr, cpsr), > - > - TP_STRUCT__entry( > - __field( unsigned long, vcpu_pc ) > - __field( unsigned long, instr ) > - __field( unsigned long, cpsr ) > - ), > - > - TP_fast_assign( > - __entry->vcpu_pc = vcpu_pc; > - __entry->instr = instr; > - __entry->cpsr = cpsr; > - ), > - > - TP_printk("Emulate MMIO at: 0x%08lx (instr: %08lx, cpsr: %08lx)", > - __entry->vcpu_pc, __entry->instr, __entry->cpsr) > -); > - > TRACE_EVENT(kvm_unmap_hva_range, > TP_PROTO(unsigned long start, unsigned long end), > TP_ARGS(start, end), >