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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 5AEB7C433DB for ; Mon, 1 Feb 2021 23:10:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 292E164EAA for ; Mon, 1 Feb 2021 23:10:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230000AbhBAXK3 (ORCPT ); Mon, 1 Feb 2021 18:10:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230002AbhBAXK1 (ORCPT ); Mon, 1 Feb 2021 18:10:27 -0500 Received: from mail-pj1-x1034.google.com (mail-pj1-x1034.google.com [IPv6:2607:f8b0:4864:20::1034]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C22F4C0613D6 for ; Mon, 1 Feb 2021 15:09:47 -0800 (PST) Received: by mail-pj1-x1034.google.com with SMTP id kx7so684815pjb.2 for ; Mon, 01 Feb 2021 15:09:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :mime-version; bh=3HKABxm2JWW8yXh6Ffuihg4FZgaqjfZi+45jOX+PQQI=; b=CcU5cvGUtNpEhVt6Zcu4H5EeWpk+/H7fNLUyevjipbJe31ZbS4kC70stdBy+qRxQuX bQGTv/PsDN4g+kKCAXTRJfbaPcAtLtu2g2G7PO0ZEND64tDUuXyPxUHFrUWJ66sQXEKP y3nKIvO2CMT9m1Olk6z3pOtYMHnAFGKkus3f9QjH3SfZp3FRkqDGNKcVfBUjYt90JoV5 PdCs3Zv1/l93Y4WGYJkTJfGuv2R5x64VDgt169TQMxHy81iven1IoQp9Pa1PwE/KPrFi owifCbIqzF5y9eiPUjgAXKU14kbZ4PlsribJAgzQV9UBoTMLxogxbFT1vqrRtcyn+Nxm BmMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:in-reply-to:message-id :references:mime-version; bh=3HKABxm2JWW8yXh6Ffuihg4FZgaqjfZi+45jOX+PQQI=; b=pWjXqCboWhrGCsUvxhn1VzGLFu8BZzJksOP83hQuOundoc9oGIaVwcZIq5VDCibyxx rPjG8wGOpo+DJg3uB2xV/GSuWQfV6aYdwcJv9faJ7MxPrVnlAMBML91+d8gmBwUIJRVh jP56c99vM2Z9qM8AN5WhAyb7uVOzrVTrAli/bRVkqHtuj26Ek6nqRcEaV+AiaVe5IEgF Cly68ivpule6+hg182B59wYIqLb/PJyhlwvT2FA5IGpT8/awAp0kitPGrW6DiSXLe7ls Aw5QOWCFKZhV6jYf/SmSAG7FqSrVwmcO1ZF1Y8S5UL+qE1xczKMRtEdjMi7+R9R/oF70 9gVw== X-Gm-Message-State: AOAM530zmbT070xHCXar/d0GFRIUzXC5+l95pg9Zqj0C1Ve/y7TQHLSW 8/wPxHFnAaCOTcWTwAXIIVqlHw== X-Google-Smtp-Source: ABdhPJyDaMvGR69SgB9QhG+gcyPBnwjWdXTx/YCd/XS+/X4S/yx5a3E3r1Y0cpZQ0HRKfgAXvzW+NQ== X-Received: by 2002:a17:902:70c6:b029:df:d62a:8c69 with SMTP id l6-20020a17090270c6b02900dfd62a8c69mr19315852plt.20.1612220986962; Mon, 01 Feb 2021 15:09:46 -0800 (PST) Received: from [2620:15c:17:3:4a0f:cfff:fe51:6667] ([2620:15c:17:3:4a0f:cfff:fe51:6667]) by smtp.gmail.com with ESMTPSA id j4sm13872905pfa.131.2021.02.01.15.09.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Feb 2021 15:09:46 -0800 (PST) Date: Mon, 1 Feb 2021 15:09:45 -0800 (PST) From: David Rientjes To: Ben Widawsky cc: linux-cxl@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-pci@vger.kernel.org, Bjorn Helgaas , Chris Browy , Christoph Hellwig , Dan Williams , Ira Weiny , Jon Masters , Jonathan Cameron , Rafael Wysocki , Randy Dunlap , Vishal Verma , daniel.lll@alibaba-inc.com, "John Groves (jgroves)" , "Kelley, Sean V" Subject: Re: [PATCH 03/14] cxl/mem: Find device capabilities In-Reply-To: <20210201225052.vrrvuxrsgmddjzbb@intel.com> Message-ID: <79b98f60-151b-6c80-65c3-91a37699d121@google.com> References: <20210130002438.1872527-1-ben.widawsky@intel.com> <20210130002438.1872527-4-ben.widawsky@intel.com> <234711bf-c03f-9aca-e0b5-ca677add3ea@google.com> <20210201165352.wi7tzpnd4ymxlms4@intel.com> <32f33dd-97a-8b1c-d488-e5198a3d7748@google.com> <20210201215857.ud5cpg7hbxj2j5bx@intel.com> <20210201222859.lzw3gvxuqebukvr6@intel.com> <20210201223314.qh24uxd7ajdppgfl@intel.com> <20210201225052.vrrvuxrsgmddjzbb@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, 1 Feb 2021, Ben Widawsky wrote: > > I think that's what 8.2.8.4.3 says, no? And then 8.2.8.4.5 says you > > can use up to Payload Size. That's why my recommendation was to enforce > > this in cxl_mem_setup_mailbox() up front. > > Yeah. I asked our spec people to update 8.2.8.4.5 to make it clearer. I'd argue > the intent is how you describe it, but the implementation isn't. > > My argument was silly anyway because if you specify greater than 1M as your > payload, you will get EINVAL at the ioctl. > > The value of how it works today is the driver will at least bind and allow you > to interact with it. > > How strongly do you feel about this? > I haven't seen the update to 8.2.8.4.5 to know yet :) You make a good point of at least being able to interact with the driver. I think you could argue that if the driver binds, then the payload size is accepted, in which case it would be strange to get an EINVAL when using the ioctl with anything >1MB. Concern was that if we mask off the reserved bits from the command register that we could be masking part of the payload size that is being passed if the accepted max is >1MB. Idea was to avoid any possibility of this inconsistency. If this is being checked for ioctl, seems like it's checking reserved bits. But maybe I should just wait for the spec update.