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 9A661C433EF for ; Thu, 5 May 2022 13:34:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241136AbiEENiI (ORCPT ); Thu, 5 May 2022 09:38:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50778 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233559AbiEENiG (ORCPT ); Thu, 5 May 2022 09:38:06 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2CDFB1AD99 for ; Thu, 5 May 2022 06:34:27 -0700 (PDT) Received: from dggpemm500023.china.huawei.com (unknown [172.30.72.53]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4KvF5D5PwWz1JBYf; Thu, 5 May 2022 21:33:20 +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, 5 May 2022 21:34:25 +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, 5 May 2022 21:34:24 +0800 Subject: Re: [PATCH v3] arm64: add the printing of tpidr_elx in __show_regs() From: "Leizhen (ThunderTown)" To: Mark Rutland CC: Catalin Marinas , Will Deacon , , References: <20220505095640.312-1-thunder.leizhen@huawei.com> Message-ID: <307e4def-1e4a-1110-e644-d485b9959ab1@huawei.com> Date: Thu, 5 May 2022 21:34:24 +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: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) 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 2022/5/5 21:26, Leizhen (ThunderTown) wrote: > > > On 2022/5/5 21:04, Mark Rutland wrote: >> On Thu, May 05, 2022 at 05:56:40PM +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 | 5 +++++ >>> 1 file changed, 5 insertions(+) >>> >>> v2 --> v3: >>> 1) Relace "switch (read_sysreg(CurrentEL))" statement with >>> "if (is_kernel_in_hyp_mode())" statement. >>> 2) Change the register name to lowercase. >>> >>> 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 7fa97df55e3ad3f..7b6bccce9721c36 100644 >>> --- a/arch/arm64/kernel/process.c >>> +++ b/arch/arm64/kernel/process.c >>> @@ -216,6 +216,11 @@ void __show_regs(struct pt_regs *regs) >>> show_regs_print_info(KERN_DEFAULT); >>> print_pstate(regs); >>> >>> + if (is_kernel_in_hyp_mode()) >>> + printk("tpidr_el2 : %016llx\n", read_sysreg(tpidr_el2)); >>> + else >>> + printk("tpidr_el1 : %016llx\n", read_sysreg(tpidr_el1)); >> >> If we care about the offset specifically, this would be simpler as: >> >> printk("cpu offset : 0x%016lx\n", __my_cpu_offset()); > > The function name is __show_regs(), so not using register name may not be good. > In fact, some other architectures may also have this problem. If we use my_cpu_offset, > we may need to put it in a public. The other idea is to back up each my_cpu_offset in an array. In this way, the offset can be queried through vmcore even if it is not printed. > >> >> ... which should do the right thing even if we repurpose the TPIDRs and move the offset elsewhere. >> >> As Will says, we should only log this for !user_mode(regs), so it could >> be placed in the block below, immediately before we print the kernel PC, i.e. >> >> if (!user_mode_regs) { >> printk("cpu offset : %016lx\n", __my_cpu_offset()); >> printk("pc : %pS\n", (void *)regs->pc); >> printk("lr : %pS\n", (void *)ptrauth_strip_insn_pac(lr)); >> ... >> } >> >> ... or in a separate block which checks the same condition. >> >> Thanks, >> Mark. >> >>> + >>> if (!user_mode(regs)) { >>> printk("pc : %pS\n", (void *)regs->pc); >>> printk("lr : %pS\n", (void *)ptrauth_strip_insn_pac(lr)); >>> -- >>> 2.25.1 >>> >> . >> > -- Regards, Zhen Lei