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=-6.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=ham 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 7B70DC43381 for ; Thu, 14 Feb 2019 23:49:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3D62621B68 for ; Thu, 14 Feb 2019 23:49:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=wdc.com header.i=@wdc.com header.b="WMZaNkXL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729406AbfBNXtL (ORCPT ); Thu, 14 Feb 2019 18:49:11 -0500 Received: from esa4.hgst.iphmx.com ([216.71.154.42]:38113 "EHLO esa4.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726178AbfBNXtL (ORCPT ); Thu, 14 Feb 2019 18:49:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=wdc.com; i=@wdc.com; q=dns/txt; s=dkim.wdc.com; t=1550188151; x=1581724151; h=subject:to:cc:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=m/m/GY5maHFTnaGubRna8IuXMU1j8X4Gcoz2PKN+T5s=; b=WMZaNkXLAooddOH/sEUfbr7zsfb3pKqLIra82v6w3GGn6crRg749VUkX xGpOe2Oq6SAAN23vUXTfI1HyBVnbe/FYjAbuK5Oc5Tti6U0ZeXJ5sheXu MNSMJkx8nrLUSbuZLQBEi4dF8IhooydsBbhIdHCYrbdVBrhIN1pMvV41o DkMHlpsRic2gBKxBpJm8bleMPc3H77AX/nHGGDqiREnIDajkrKolK/E+U DK2wSrtZfOXGAKqJeFJEXnU/2bXKiYmvfVutVimubLpARpC3ZkgiYdXle OC/TP0oQBdOXE+HMgdjQVeZ2UlKUz2vvYTPh/cVc6j2uCobOTamAfo92/ Q==; X-IronPort-AV: E=Sophos;i="5.58,370,1544457600"; d="scan'208";a="101282672" Received: from uls-op-cesaip01.wdc.com (HELO uls-op-cesaep01.wdc.com) ([199.255.45.14]) by ob1.hgst.iphmx.com with ESMTP; 15 Feb 2019 07:49:10 +0800 Received: from uls-op-cesaip02.wdc.com ([10.248.3.37]) by uls-op-cesaep01.wdc.com with ESMTP; 14 Feb 2019 15:27:41 -0800 Received: from c02v91rdhtd5.sdcorp.global.sandisk.com (HELO [10.111.66.47]) ([10.111.66.47]) by uls-op-cesaip02.wdc.com with ESMTP; 14 Feb 2019 15:49:10 -0800 Subject: Re: [v4 PATCH 8/8] RISC-V: Assign hwcap as per comman capabilities. To: Palmer Dabbelt , "johan@kernel.org" Cc: "robh@kernel.org" , "aou@eecs.berkeley.edu" , "jason@lakedaemon.net" , "alankao@andestech.com" , "dmitriy@oss-tech.org" , "schwab@suse.de" , "daniel.lezcano@linaro.org" , "linux-kernel@vger.kernel.org" , "marc.zyngier@arm.com" , Paul Walmsley , "anup@brainfault.org" , "linux-riscv@lists.infradead.org" , "tglx@linutronix.de" References: From: Atish Patra Message-ID: Date: Thu, 14 Feb 2019 15:49:09 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/13/19 4:38 PM, Palmer Dabbelt wrote: > On Wed, 13 Feb 2019 00:44:42 PST (-0800), johan@kernel.org wrote: >> On Tue, Feb 12, 2019 at 11:58:10AM -0800, Atish Patra wrote: >>> On 2/12/19 3:25 AM, Johan Hovold wrote: >>>> On Tue, Feb 12, 2019 at 03:10:12AM -0800, Atish Patra wrote: >>>>> Currently, we set hwcap based on first valid hart from DT. This may not >>>>> be correct always as that hart might not be current booting cpu or may >>>>> have a different capability. >>>>> >>>>> Set hwcap as the capabilities supported by all possible harts with "okay" >>>>> status. >>>>> >>>>> Signed-off-by: Atish Patra >>>>> --- >>>>> arch/riscv/kernel/cpufeature.c | 41 ++++++++++++++++++++++------------------- >>>>> 1 file changed, 22 insertions(+), 19 deletions(-) >>>>> >>>>> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c >>>>> index e7a4701f..a1e4fb34 100644 >>>>> --- a/arch/riscv/kernel/cpufeature.c >>>>> +++ b/arch/riscv/kernel/cpufeature.c >>>>> @@ -20,6 +20,7 @@ >>>>> #include >>>>> #include >>>>> #include >>>>> +#include >>>>> >>>>> unsigned long elf_hwcap __read_mostly; >>>>> #ifdef CONFIG_FPU >>>>> @@ -42,28 +43,30 @@ void riscv_fill_hwcap(void) >>>>> >>>>> elf_hwcap = 0; >>>>> >>>>> - /* >>>>> - * We don't support running Linux on hertergenous ISA systems. For >>>>> - * now, we just check the ISA of the first "okay" processor. >>>>> - */ >>>>> for_each_of_cpu_node(node) { >>>>> - if (riscv_of_processor_hartid(node) >= 0) >>>>> - break; >>>>> - } >>>>> - if (!node) { >>>>> - pr_warn("Unable to find \"cpu\" devicetree entry\n"); >>>>> - return; >>>>> - } >>>>> + unsigned long this_hwcap = 0; >>>>> >>>>> - if (of_property_read_string(node, "riscv,isa", &isa)) { >>>>> - pr_warn("Unable to find \"riscv,isa\" devicetree entry\n"); >>>>> - of_node_put(node); >>>>> - return; >>>>> - } >>>>> - of_node_put(node); >>>>> + if (riscv_of_processor_hartid(node) < 0) >>>>> + continue; >>>>> >>> >>>>> - for (i = 0; i < strlen(isa); ++i) >>>>> - elf_hwcap |= isa2hwcap[(unsigned char)(isa[i])]; >>>>> + if (of_property_read_string(node, "riscv,isa", &isa)) { >>>>> + pr_warn("Unable to find \"riscv,isa\" devicetree entry\n"); >>>>> + return; >>>> >>>> Did you want "continue" here to continue processing the other harts? >>> >>> Hmm. If a cpu node doesn't have isa in DT, that means DT is wrong. A >>> "continue" here will let user space use other harts just with a warning >>> message? >>> >>> Returning here will not set elf_hwcap which forces the user to fix the >>> DT. I am not sure what should be the defined behavior in this case. >>> >>> Any thoughts ? >> >> The problem is that the proposed code might still set elf_hwcap -- it >> all depends on the order of the hart nodes in dt (i.e. it will only be >> left unset if the first node is malformed). >> >> For that reason, I'd say it's better to either bail out (hard or at >> least with elf_hwcap unset) or to continue processing the other nodes. >> >> The former might break current systems with malformed dt, though. >> >> And since the harts are expected to have the same ISA, continuing the >> processing while warning and ignoring the malformed node might be >> acceptable. > > Handling malformed device trees by providing a warning and an empty HWCAP seems > like the right way to go to me. > If I understand you correctly, you prefer following things to be done in case of malformed DT. 1. Print a warning message 2. Unset the entire HWCAP 3. Return without processing other harts. This will most likely result in panic when user space starts. Is this correct ? Regards, Atish >> >> Johan >