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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 73914C47255 for ; Mon, 11 May 2020 11:00:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5493B20801 for ; Mon, 11 May 2020 11:00:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729560AbgEKLAZ (ORCPT ); Mon, 11 May 2020 07:00:25 -0400 Received: from foss.arm.com ([217.140.110.172]:56324 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729556AbgEKLAZ (ORCPT ); Mon, 11 May 2020 07:00:25 -0400 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 4AD751FB; Mon, 11 May 2020 04:00:24 -0700 (PDT) Received: from gaia (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DFC143F305; Mon, 11 May 2020 04:00:20 -0700 (PDT) Date: Mon, 11 May 2020 12:00:14 +0100 From: Catalin Marinas To: Will Deacon Cc: Christoph Hellwig , james.morse@arm.com, Andrew Morton , Arnd Bergmann , Roman Zippel , Jessica Yu , Michal Simek , x86@kernel.org, linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-c6x-dev@linux-c6x.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-um@lists.infradead.org, linux-xtensa@linux-xtensa.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 02/31] arm64: fix the flush_icache_range arguments in machine_kexec Message-ID: <20200511110014.GA19176@gaia> References: <20200510075510.987823-1-hch@lst.de> <20200510075510.987823-3-hch@lst.de> <20200511075115.GA16134@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200511075115.GA16134@willie-the-truck> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-m68k-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org On Mon, May 11, 2020 at 08:51:15AM +0100, Will Deacon wrote: > On Sun, May 10, 2020 at 09:54:41AM +0200, Christoph Hellwig wrote: > > The second argument is the end "pointer", not the length. > > > > Signed-off-by: Christoph Hellwig > > --- > > arch/arm64/kernel/machine_kexec.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c > > index 8e9c924423b4e..a0b144cfaea71 100644 > > --- a/arch/arm64/kernel/machine_kexec.c > > +++ b/arch/arm64/kernel/machine_kexec.c > > @@ -177,6 +177,7 @@ void machine_kexec(struct kimage *kimage) > > * the offline CPUs. Therefore, we must use the __* variant here. > > */ > > __flush_icache_range((uintptr_t)reboot_code_buffer, > > + (uintptr_t)reboot_code_buffer + > > arm64_relocate_new_kernel_size); > > Urgh, well spotted. It's annoyingly different from __flush_dcache_area(). > > But now I'm wondering what this code actually does... the loop condition > in invalidate_icache_by_line works with 64-bit arithmetic, so we could > spend a /very/ long time here afaict. I think it goes through the loop only once. The 'b.lo' saves us here. OTOH, there is no I-cache maintenance done. > It's also a bit annoying that we do a bunch of redundant D-cache > maintenance too. Should we use invalidate_icache_range() here instead? Since we have the __flush_dcache_area() above it for cleaning to PoC, we could use invalidate_icache_range() here. We probably didn't have this function at the time, it was added for KVM (commit 4fee94736603cd6). > (and why does that thing need to toggle uaccess)? invalidate_icache_range() doesn't need to, it works on the kernel linear map. __flush_icache_range() doesn't need to either, that's a side-effect of the fall-through implementation. Anyway, I think Christoph's patch needs to go in with a fixes tag: Fixes: d28f6df1305a ("arm64/kexec: Add core kexec support") Cc: # 4.8.x- and we'll change these functions/helpers going forward for arm64. Happy to pick this up via the arm64 for-next/fixes branch. -- Catalin