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=-8.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 B342CC433E0 for ; Thu, 11 Feb 2021 16:09:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F68F64E74 for ; Thu, 11 Feb 2021 16:09:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230337AbhBKQIv (ORCPT ); Thu, 11 Feb 2021 11:08:51 -0500 Received: from mga17.intel.com ([192.55.52.151]:8125 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231518AbhBKQGX (ORCPT ); Thu, 11 Feb 2021 11:06:23 -0500 IronPort-SDR: Me4tdqzlpicdY4pTb4E+5U7KGErt+88IMspaScAwP29nIZfrVLvLZcRMh4aMBCeuMbMkZLSAkN XIKA9++MsNmQ== X-IronPort-AV: E=McAfee;i="6000,8403,9892"; a="162016589" X-IronPort-AV: E=Sophos;i="5.81,170,1610438400"; d="scan'208";a="162016589" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Feb 2021 08:04:38 -0800 IronPort-SDR: kQh2KysLd/vC5jPu93cDLmW2HWsnxnA1xndKMfK9uDSK6541kBYwVPYGyGzq2NHqFypOeB95A0 PL7J7I7hj0MA== X-IronPort-AV: E=Sophos;i="5.81,170,1610438400"; d="scan'208";a="380716457" Received: from reknight-mobl.amr.corp.intel.com (HELO intel.com) ([10.252.134.254]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Feb 2021 08:04:37 -0800 Date: Thu, 11 Feb 2021 08:04:36 -0800 From: Ben Widawsky To: Jonathan Cameron Cc: Dan Williams , linux-cxl@vger.kernel.org, Linux ACPI , Linux Kernel Mailing List , linux-nvdimm , Linux PCI , Bjorn Helgaas , Chris Browy , Christoph Hellwig , David Hildenbrand , David Rientjes , Ira Weiny , Jon Masters , Rafael Wysocki , Randy Dunlap , Vishal Verma , "John Groves (jgroves)" , "Kelley, Sean V" Subject: Re: [PATCH v2 2/8] cxl/mem: Find device capabilities Message-ID: <20210211160436.qbvgfzqng37erwae@intel.com> References: <20210210000259.635748-1-ben.widawsky@intel.com> <20210210000259.635748-3-ben.widawsky@intel.com> <20210210174104.0000710a@Huawei.com> <20210210185319.chharluce2ly4cne@intel.com> <20210211100152.00000667@Huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210211100152.00000667@Huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org On 21-02-11 10:01:52, Jonathan Cameron wrote: > On Wed, 10 Feb 2021 11:54:29 -0800 > Dan Williams wrote: > > > > > ... > > > > > > > > > +static void cxl_mem_mbox_timeout(struct cxl_mem *cxlm, > > > > > + struct mbox_cmd *mbox_cmd) > > > > > +{ > > > > > + struct device *dev = &cxlm->pdev->dev; > > > > > + > > > > > + dev_dbg(dev, "Mailbox command (opcode: %#x size: %zub) timed out\n", > > > > > + mbox_cmd->opcode, mbox_cmd->size_in); > > > > > + > > > > > + if (IS_ENABLED(CONFIG_CXL_MEM_INSECURE_DEBUG)) { > > > > > > > > Hmm. Whilst I can see the advantage of this for debug, I'm not sure we want > > > > it upstream even under a rather evil looking CONFIG variable. > > > > > > > > Is there a bigger lock we can use to avoid chance of accidental enablement? > > > > > > Any suggestions? I'm told this functionality was extremely valuable for NVDIMM, > > > though I haven't personally experienced it. > > > > Yeah, there was no problem with the identical mechanism in LIBNVDIMM > > land. However, I notice that the useful feature for LIBNVDIMM is the > > option to dump all payloads. This one only fires on timeouts which is > > less useful. So I'd say fix it to dump all payloads on the argument > > that the safety mechanism was proven with the LIBNVDIMM precedent, or > > delete it altogether to maintain v5.12 momentum. Payload dumping can > > be added later. > > I think I'd drop it for now - feels like a topic that needs more discussion. > > Also, dumping this data to the kernel log isn't exactly elegant - particularly > if we dump a lot more of it. Perhaps tracepoints? > I'll drop it. It's also a small enough bit to add on for developers. When I post v3, I will add that bit on top as an RFC. My personal preference FWIW is to use debugfs to store the payload of the last executed command. We went with this because of the mechanism's provenance (libnvdimm) > > > > [..] > > > > > diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h > > > > > index e709ae8235e7..6267ca9ae683 100644 > > > > > --- a/include/uapi/linux/pci_regs.h > > > > > +++ b/include/uapi/linux/pci_regs.h > > > > > @@ -1080,6 +1080,7 @@ > > > > > > > > > > /* Designated Vendor-Specific (DVSEC, PCI_EXT_CAP_ID_DVSEC) */ > > > > > #define PCI_DVSEC_HEADER1 0x4 /* Designated Vendor-Specific Header1 */ > > > > > +#define PCI_DVSEC_HEADER1_LENGTH_MASK 0xFFF00000 > > > > > > > > Seems sensible to add the revision mask as well. > > > > The vendor id currently read using a word read rather than dword, but perhaps > > > > neater to add that as well for completeness? > > > > > > > > Having said that, given Bjorn's comment on clashes and the fact he'd rather see > > > > this stuff defined in drivers and combined later (see review patch 1 and follow > > > > the link) perhaps this series should not touch this header at all. > > > > > > I'm fine to move it back. > > > > Yeah, we're playing tennis now between Bjorn's and Christoph's > > comments, but I like Bjorn's suggestion of "deduplicate post merge" > > given the bloom of DVSEC infrastructure landing at the same time. > I guess it may depend on timing of this. Personally I think 5.12 may be too aggressive. > > As long as Bjorn can take a DVSEC deduplication as an immutable branch then perhaps > during 5.13 this tree can sit on top of that. > > Jonathan > >