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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 73B25C6FA82 for ; Wed, 21 Sep 2022 00:08:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231354AbiIUAIa (ORCPT ); Tue, 20 Sep 2022 20:08:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37198 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230511AbiIUAI1 (ORCPT ); Tue, 20 Sep 2022 20:08:27 -0400 Received: from mail-pl1-x62c.google.com (mail-pl1-x62c.google.com [IPv6:2607:f8b0:4864:20::62c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E8DF66113E for ; Tue, 20 Sep 2022 17:08:25 -0700 (PDT) Received: by mail-pl1-x62c.google.com with SMTP id t3so4024556ply.2 for ; Tue, 20 Sep 2022 17:08:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date; bh=P+2TPNWdXXOCWAvqTb/n3Y3lh5Lh38PVwp86QKZPW/U=; b=l79CvKW56MUCcXospEUz9HzLbq84Cfb4nvfiZqwlGWLuDvqwo4gFUQugO1KgXZ9Feg F5QakQ/sjeAhCMC9RQW4hR6FDddJHvpXKeOgn212CjqVjQ8lXWaQka6F+KDFmCtzUUFp 886SmNU7eIDMwzOpAT29RFKvf+9dHNdY++bxzgSoE325sin8U4JmiBfqbOLUOgsuN+IB r5UKnDBMDxzngTWqQF8pu8lKhOXBWgwmc0yJdTx9JnyvITwzRwBJ0eYao/RNdCt6Xi5y jiathpY5irAfSmUkcV7YbeQT23gXpZ35jag3sLF87/vV36PSAfyOFfr0EVFCrePSB/vu 7WFA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=P+2TPNWdXXOCWAvqTb/n3Y3lh5Lh38PVwp86QKZPW/U=; b=aLTgN7P7MSyMvOcIHj4d5/PzDsTdRkI68z1hTQzZ37AR4VoxSmQ9g8Z6u7X244Tn8L 1kCYXvVA9jPyTPGutkIVgZVtkxEdGYs2wTW+X98zl2Dv0aX8OfMsTDaJfPJXMJDjCwt7 T3GolObuBdmpZaSBPhd6HYW5E5pZsAWNNRmgYKKq8XqRBFUhC6exjczG/Jfn9bfFFZtO 2NMv0YNBmh+OoYeJcmTZrNNfsnXlk2bQzsbbOYMZPqV1fgYCkYx+NjAeesutAx+E27Si 7AySKAZc4f0sJMwxWLje2n0RuNh7YK0PPmjnQ5zQG7qlMKlsfHTgJ7HU16VAdHKNBI5W BPEw== X-Gm-Message-State: ACrzQf25V0shKCAdOTFxqKekUd/Ht25POUdVXkAo+0w2v+GbJTuuxqi9 1xV+MXKCZV2tPS3eTaW6HArMylAItKls4TrDGQyatA== X-Google-Smtp-Source: AMsMyM7Hq+eK82DO64bRlQggpPM3rRQhxkz+7K4Da9DMNHl9amBFdTiPYROgJVmKyMQhJXyZ+2seMh8dbNV5Qz4qacQ= X-Received: by 2002:a17:902:d2c4:b0:178:32c4:6648 with SMTP id n4-20020a170902d2c400b0017832c46648mr2115146plc.88.1663718905205; Tue, 20 Sep 2022 17:08:25 -0700 (PDT) MIME-Version: 1.0 References: <20220920082005.2459826-1-denik@chromium.org> <877d1yl797.wl-maz@kernel.org> In-Reply-To: <877d1yl797.wl-maz@kernel.org> From: Denis Nikitin Date: Tue, 20 Sep 2022 17:08:09 -0700 Message-ID: Subject: Re: [PATCH] KVM: arm64: nvhe: Disable profile optimization To: Marc Zyngier Cc: Denis Nikitin , Catalin Marinas , Will Deacon , James Morse , Alexandru Elisei , Nick Desaulniers , Manoj Gupta , David Brazdil , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mark, Thank you for a quick response. On Tue, Sep 20, 2022 at 2:34 AM Marc Zyngier wrote: > > Hi Denis, > > On Tue, 20 Sep 2022 09:20:05 +0100, > Denis Nikitin wrote: > > > > Kernel build with -fprofile-sample-use raises the following failure: > > > > error: arch/arm64/kvm/hyp/nvhe/kvm_nvhe.tmp.o: Unexpected SHT_REL > > section ".rel.llvm.call-graph-profile" > > How is this flag provided? I don't see any occurrence of it in the > kernel so far. On ChromeOS we build the kernel with sample profiles by adding -fprofile-sample-use=/path/to/gcov.profile to KCFLAGS. > > > > > SHT_REL is generated by the latest lld, see > > https://reviews.llvm.org/rGca3bdb57fa1ac98b711a735de048c12b5fdd8086. > > Is this part of a released toolchain? If so, can you spell out the > first version where this occurs? Yes, it was added in llvm-13. I will update the patch. > > > Disable profile optimization in kvm/nvhe to fix the build with > > AutoFDO. > > It'd be good to at least mention how AutoFDO and -fprofile-sample-use > relate to each other. Good point. AutoFDO is an example of sample profiles. It's not actually relevant for the bug. I will better remove it. > > > > > Signed-off-by: Denis Nikitin > > --- > > arch/arm64/kvm/hyp/nvhe/Makefile | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile > > index b5c5119c7396..6a6188374a52 100644 > > --- a/arch/arm64/kvm/hyp/nvhe/Makefile > > +++ b/arch/arm64/kvm/hyp/nvhe/Makefile > > @@ -89,6 +89,9 @@ quiet_cmd_hypcopy = HYPCOPY $@ > > # Remove ftrace, Shadow Call Stack, and CFI CFLAGS. > > # This is equivalent to the 'notrace', '__noscs', and '__nocfi' annotations. > > KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) $(CC_FLAGS_CFI), $(KBUILD_CFLAGS)) > > +# Profile optimization creates SHT_REL section '.llvm.call-graph-profile' for > > +# the hot code. SHT_REL is currently not supported by the KVM tools. > > 'KVM tools' seems vague. Maybe call out the actual helper that > processes the relocations? Agreed. > > > +KBUILD_CFLAGS += $(call cc-option,-fno-profile-sample-use,-fno-profile-use) > > Why adding these options instead of filtering out the offending option > as it is done just above? That was actually the alternative solution and it worked as well. Let me double check if profile optimization doesn't mess up with other sections and if it doesn't I will remove the '.llvm.call-graph-profile' section instead. > > Also, is this the only place the kernel fails to compile? The EFI stub > does similar things AFAIR, and could potentially fail the same way. This was the only place in 5.15 where we tested it. Let me see if EFI has this section. > > Thanks, > > M. > > -- > Without deviation from the norm, progress is not possible. Thanks, Denis