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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jdlmp-0002a6-4v; Wed, 27 May 2020 02:27:19 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jdlml-0002Yq-Iw for linux-arm-kernel@lists.infradead.org; Wed, 27 May 2020 02:27:16 +0000 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 DB3BA30E; Tue, 26 May 2020 19:27:12 -0700 (PDT) Received: from [10.163.76.100] (unknown [10.163.76.100]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B36143F52E; Tue, 26 May 2020 19:27:10 -0700 (PDT) Subject: Re: [PATCH V2] arm64/cpufeature: Add get_arm64_ftr_reg_nowarn() To: Will Deacon , Catalin Marinas References: <1590500353-28082-1-git-send-email-anshuman.khandual@arm.com> <20200526150135.GI17051@gaia> <20200526194648.GA2206@willie-the-truck> From: Anshuman Khandual Message-ID: Date: Wed, 27 May 2020 07:56:30 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200526194648.GA2206@willie-the-truck> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200526_192715_668591_C857526F X-CRM114-Status: GOOD ( 13.07 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, Mark Brown , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Suzuki K Poulose Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 05/27/2020 01:16 AM, Will Deacon wrote: > On Tue, May 26, 2020 at 04:01:35PM +0100, Catalin Marinas wrote: >> On Tue, May 26, 2020 at 07:09:13PM +0530, Anshuman Khandual wrote: >>> @@ -632,8 +654,6 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) >>> const struct arm64_ftr_bits *ftrp; >>> struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg); >>> >>> - BUG_ON(!reg); >>> - >>> for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) { >>> u64 ftr_mask = arm64_ftr_mask(ftrp); >>> s64 ftr_new = arm64_ftr_value(ftrp, new); >>> @@ -762,7 +782,6 @@ static int check_update_ftr_reg(u32 sys_id, int cpu, u64 val, u64 boot) >>> { >>> struct arm64_ftr_reg *regp = get_arm64_ftr_reg(sys_id); >>> >>> - BUG_ON(!regp); >>> update_cpu_ftr_reg(regp, val); >>> if ((boot & regp->strict_mask) == (val & regp->strict_mask)) >>> return 0; >>> @@ -776,9 +795,6 @@ static void relax_cpu_ftr_reg(u32 sys_id, int field) >>> const struct arm64_ftr_bits *ftrp; >>> struct arm64_ftr_reg *regp = get_arm64_ftr_reg(sys_id); >>> >>> - if (WARN_ON(!regp)) >>> - return; >> >> I think Will wanted an early return in all these functions not just >> removing the BUG_ON(). I'll let him clarify. > > Yes, the callers need to check the pointer and return early. Sure, will do. But for check_update_ftr_reg(), a feature register search failure should be treated as a success (0) or a failure (1). What should it return ? Seems bit tricky, as there are good reasons to go either way. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel