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 A9F47C433EF for ; Thu, 28 Apr 2022 11:08:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344393AbiD1LLN (ORCPT ); Thu, 28 Apr 2022 07:11:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53414 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231407AbiD1LLI (ORCPT ); Thu, 28 Apr 2022 07:11:08 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 81661BE32 for ; Thu, 28 Apr 2022 04:07:54 -0700 (PDT) Received: from dggpemm500023.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4KptBD5mJczhYfc; Thu, 28 Apr 2022 19:07:32 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500023.china.huawei.com (7.185.36.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 28 Apr 2022 19:07:52 +0800 Received: from [10.174.178.55] (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 28 Apr 2022 19:07:52 +0800 Subject: Re: [PATCH v2] arm64: add the printing of tpidr_elx in __show_regs() To: Will Deacon CC: Catalin Marinas , , , "James Morse" References: <20220316062408.1113-1-thunder.leizhen@huawei.com> <20220428102156.GA14123@willie-the-truck> From: "Leizhen (ThunderTown)" Message-ID: <4c956c17-6e13-37a1-7da3-b2c8243c2c01@huawei.com> Date: Thu, 28 Apr 2022 19:07:51 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20220428102156.GA14123@willie-the-truck> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/4/28 18:21, Will Deacon wrote: > On Wed, Mar 16, 2022 at 02:24:08PM +0800, Zhen Lei wrote: >> Commit 7158627686f0 ("arm64: percpu: implement optimised pcpu access >> using tpidr_el1") and commit 6d99b68933fb ("arm64: alternatives: use >> tpidr_el2 on VHE hosts") use tpidr_elx to cache my_cpu_offset to optimize >> pcpu access. However, when performing reverse execution based on the >> registers and the memory contents in kdump, this information is sometimes >> required if there is a pcpu access. >> >> Signed-off-by: Zhen Lei >> --- >> arch/arm64/kernel/process.c | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> v1 --> v2: >> Directly print the tpidr_elx register of the current exception level. >> Avoid coupling with the implementation of 'my_cpu_offset'. >> >> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c >> index 5369e649fa79ff8..738932e6fa4e947 100644 >> --- a/arch/arm64/kernel/process.c >> +++ b/arch/arm64/kernel/process.c >> @@ -216,6 +216,17 @@ void __show_regs(struct pt_regs *regs) >> show_regs_print_info(KERN_DEFAULT); >> print_pstate(regs); >> >> + switch (read_sysreg(CurrentEL)) { > > This should use is_kernel_in_hyp_mode() to detect if we're running at El2. > >> + case CurrentEL_EL1: >> + printk("tpidr_el1 : %016llx\n", read_sysreg(TPIDR_EL1)); >> + break; >> + case CurrentEL_EL2: >> + printk("tpidr_el2 : %016llx\n", read_sysreg(TPIDR_EL2)); >> + break; >> + default: >> + break; >> + } > > I think this path can be triggered directly from usermode, so we really > shouldn't be printing raw kernel virtual addresses here. I run echo c > /proc/sysrq-trigger and didn't trigger this path, but maybe there's another way. Analysis from the other side, except for the instruction address, all generic registers r0-r31 is output as raw. There's also an opportunity to contain the instruction address. So how about: + if (oops_in_progress) + printk("tpidr : %016lx\n", __my_cpu_offset); > > Will > . > -- Regards, Zhen Lei