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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 33896C43331 for ; Sat, 7 Sep 2019 10:05:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 16CCE20854 for ; Sat, 7 Sep 2019 10:05:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730171AbfIGKFu (ORCPT ); Sat, 7 Sep 2019 06:05:50 -0400 Received: from foss.arm.com ([217.140.110.172]:35908 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726012AbfIGKFt (ORCPT ); Sat, 7 Sep 2019 06:05:49 -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 DA1641576; Sat, 7 Sep 2019 03:05:48 -0700 (PDT) Received: from [10.37.12.3] (unknown [10.37.12.3]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 85A3F3F59C; Sat, 7 Sep 2019 03:05:46 -0700 (PDT) Subject: Re: [Xen-devel] [PATCH] ARM: xen: unexport HYPERVISOR_platform_op function To: Andrew Cooper , Arnd Bergmann Cc: Stefano Stabellini , Emil Velikov , Russell King , Denis Efremov , "linux-kernel@vger.kernel.org" , Masahiro Yamada , xen-devel , Linux ARM References: <20190906153948.2160342-1-arnd@arndb.de> <7abad95e-ea47-c068-d91c-ba503f2530b9@citrix.com> From: Julien Grall Message-ID: <95dbd972-fe78-d0ca-f7b4-1a6bdd418eab@arm.com> Date: Sat, 7 Sep 2019 11:05:45 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andrew, On 9/6/19 6:20 PM, Andrew Cooper wrote: > On 06/09/2019 17:00, Arnd Bergmann wrote: >> On Fri, Sep 6, 2019 at 5:55 PM Andrew Cooper wrote: >>> On 06/09/2019 16:39, Arnd Bergmann wrote: >>>> HYPERVISOR_platform_op() is an inline function and should not >>>> be exported. Since commit 15bfc2348d54 ("modpost: check for >>>> static EXPORT_SYMBOL* functions"), this causes a warning: >>>> >>>> WARNING: "HYPERVISOR_platform_op" [vmlinux] is a static EXPORT_SYMBOL_GPL >>>> >>>> Remove the extraneous export. >>>> >>>> Fixes: 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL* functions") >>>> Signed-off-by: Arnd Bergmann >>> Something is wonky. That symbol is (/ really ought to be) in the >>> hypercall page and most definitely not inline. >>> >>> Which tree is that changeset from? I can't find the SHA. >> This is from linux-next, I think from the kbuild tree. > > Thanks. > > Julien/Stefano: Why are any of these hypercalls out-of-line?  ARM > doesn't use the hypercall page, and there is no argument translation > (not even in arm32 as there are no 5-argument hypercalls declared). I am not sure how the hypercall page makes things different. You still have to store the arguments in the correct register so... > > They'd surely be easier to implement with a few static inlines and some > common code, than to try and replicate the x86 side hypercall_page > interface ? ... I don't think they will be easier to implement with a few static inlines. The implementation will likely end up to be similar to arch/x86/asm/xen/hypercall.h. Furthermore, one of the downside of per-arch static inline is it is more difficult to ensure the prototype match for all the architectures. Although, it might be possible to make them common by only requesting per-arch to implement HYPERCALL_N(...). So I think the code is better as it is. While looking at the code, I also realized that the implementation of HYPERCALL_dm_op might be incorrect for Arm32. Similarly do privcmd call, I think dm_op call should enable user access as they will be used by userspace. We don't use dm_op on Arm so far, hence why I think this was unnoticed. I will see if I can reproduce it and send a patch. Cheers, -- Julien Grall