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=-3.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 11BD3C4741F for ; Thu, 5 Nov 2020 08:25:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B048121D7F for ; Thu, 5 Nov 2020 08:25:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604564757; bh=ong/5uAOzEPzvvkf24FqAzmWCt2WwE06vxIZsyxBPc0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=u1tdnLAT7HQ8JKpWGPebGx0Vk9/1QpltEVqz/QgMshkhI57A3tP8EMi2n+tQyfOe8 ZyHoYuR83Cga1qdbOqdX9a6BhmKiTqKfhMS9en/0ov+m/8fcZAd//cyldRbcfz2C4j U+A3y0Yl/z/e/dFnHWj2lMFGIev942nQ2KLwr3iE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729851AbgKEIZ4 (ORCPT ); Thu, 5 Nov 2020 03:25:56 -0500 Received: from mail.kernel.org ([198.145.29.99]:60506 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729604AbgKEIZ4 (ORCPT ); Thu, 5 Nov 2020 03:25:56 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5E7D8206ED; Thu, 5 Nov 2020 08:25:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604564755; bh=ong/5uAOzEPzvvkf24FqAzmWCt2WwE06vxIZsyxBPc0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vP9KXdx5k5SLy8dxikoStWRPdzZpUnXGbSNqhTu2Ymg+eD7ZimDK5qFaY1LQf595R lE5w0dD8PtjFtFKD/9VL8j0FMSeSwJSpigdZ1E75M1iCL5GHVhs4/x2mE/l+xfa3xy IlSzW9oabzBTl1TBGdilxMiZNH/O8tpjLNk1g1m8= Date: Thu, 5 Nov 2020 09:26:39 +0100 From: Greg Kroah-Hartman To: Shuo A Liu Cc: linux-kernel@vger.kernel.org, x86@kernel.org, "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Sean Christopherson , Yu Wang , Reinette Chatre , Zhi Wang , Zhenyu Wang Subject: Re: [PATCH v5 06/17] virt: acrn: Introduce VM management interfaces Message-ID: <20201105082639.GB3426404@kroah.com> References: <20201019061803.13298-1-shuo.a.liu@intel.com> <20201019061803.13298-7-shuo.a.liu@intel.com> <20201104190235.GA2855400@kroah.com> <20201105031029.GB17702@shuo-intel.sh.intel.com> <20201105062907.GA693781@kroah.com> <20201105073545.GD17702@shuo-intel.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201105073545.GD17702@shuo-intel.sh.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 05, 2020 at 03:35:45PM +0800, Shuo A Liu wrote: > On Thu 5.Nov'20 at 7:29:07 +0100, Greg Kroah-Hartman wrote: > > On Thu, Nov 05, 2020 at 11:10:29AM +0800, Shuo A Liu wrote: > > > On Wed 4.Nov'20 at 20:02:35 +0100, Greg Kroah-Hartman wrote: > > > > On Mon, Oct 19, 2020 at 02:17:52PM +0800, shuo.a.liu@intel.com wrote: > > > > > --- /dev/null > > > > > +++ b/include/uapi/linux/acrn.h > > > > > @@ -0,0 +1,56 @@ > > > > > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ > > > > > +/* > > > > > + * Userspace interface for /dev/acrn_hsm - ACRN Hypervisor Service Module > > > > > + * > > > > > + * This file can be used by applications that need to communicate with the HSM > > > > > + * via the ioctl interface. > > > > > + */ > > > > > + > > > > > +#ifndef _UAPI_ACRN_H > > > > > +#define _UAPI_ACRN_H > > > > > + > > > > > +#include > > > > > + > > > > > +/** > > > > > + * struct acrn_vm_creation - Info to create a User VM > > > > > + * @vmid: User VM ID returned from the hypervisor > > > > > + * @reserved0: Reserved > > > > > + * @vcpu_num: Number of vCPU in the VM. Return from hypervisor. > > > > > + * @reserved1: Reserved > > > > > + * @uuid: UUID of the VM. Pass to hypervisor directly. > > > > > + * @vm_flag: Flag of the VM creating. Pass to hypervisor directly. > > > > > + * @ioreq_buf: Service VM GPA of I/O request buffer. Pass to > > > > > + * hypervisor directly. > > > > > + * @cpu_affinity: CPU affinity of the VM. Pass to hypervisor directly. > > > > > + * @reserved2: Reserved > > > > > > > > Reserved and must be 0? > > > > > > Not a must. > > > > That's guaranteed to come back and bite you in the end. > > OK. I can fill them with zero before passing them to hypervisor. > > > You all have read the "how to write a good api" document, right? > > Is it Documentation/driver-api/ioctl.rst? Or i missed.. That's one good document, but no, not what I was referring to. I was thinking of Documentation/process/adding-syscalls.rst, which is what you are doing here implicitly with these new ioctls (every ioctl is a brand new syscall.) > > > > What are they reserved for? > > > > > > > > Same for all of the reserved fields, why? > > > > > > Some reserved fields are to map layout in the hypervisor side, others > > > are for future use. > > > > ioctls should not have these, again, please read the documentation. If > > you need something new in the future, just make a new ioctl. > > OK. I will remove some reserved fields for scalability. "scalability" should have nothing to do with any of this, right? What am I missing? > Though i can > keep some reserved fields for alignment (and to keep same data structure > layout with the hypervisor), right? > Documentation/driver-api/ioctl.rst says that explicit reserved fields > could be used. If you need alignment, yes, that is fine, but that's not what you are saying these are for. And if you need alignment, why not move things around so they are properly aligned. And this structure has nothing to do with the hypervisor structure, that's a internal-kernel structure, not a userspace-visable thing if you are doing things correctly. As an example of all of this type of review and conversation, please refer to the review of the recent nitro_enclaves code that got merged. All of the discussions there about ioctls are also relevant here. thanks, greg k-h