From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 40lWbN6v8NzF2fH for ; Tue, 15 May 2018 18:54:40 +1000 (AEST) Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w4F8s0LX005655 for ; Tue, 15 May 2018 04:54:37 -0400 Received: from e06smtp15.uk.ibm.com (e06smtp15.uk.ibm.com [195.75.94.111]) by mx0a-001b2d01.pphosted.com with ESMTP id 2hyreh9de8-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 15 May 2018 04:54:37 -0400 Received: from localhost by e06smtp15.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 15 May 2018 09:54:35 +0100 Subject: Re: [PATCH v4 1/2] cxl: Set the PBCQ Tunnel BAR register when enabling capi mode To: Michael Ellerman , "stewart@linux.vnet.ibm.com" , linuxppc-dev@lists.ozlabs.org References: <20180514082736.3699-1-felix@linux.ibm.com> <87sh6upl2i.fsf@concordia.ellerman.id.au> <87r2mdo57x.fsf@concordia.ellerman.id.au> Cc: fbarrat@linux.ibm.com, clombard@linux.ibm.com, benh@au1.ibm.com From: Philippe Bergheaud Date: Tue, 15 May 2018 10:54:31 +0200 MIME-Version: 1.0 In-Reply-To: <87r2mdo57x.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=windows-1252; format=flowed Message-Id: <51771ac5-02c3-0e84-eba7-855ecebcaf9d@linux.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 15/05/2018 07:30, Michael Ellerman wrote: > Philippe Bergheaud writes: > >> On 14/05/2018 12:51, Michael Ellerman wrote: >>> Philippe Bergheaud writes: >>> >>>> Skiboot used to set the default Tunnel BAR register value when capi mode >>>> was enabled. This approach was ok for the cxl driver, but prevented other >>>> drivers from choosing different values. >>>> >>>> Skiboot versions > 5.11 will not set the default value any longer. This >>>> patch modifies the cxl driver to set/reset the Tunnel BAR register when >>>> entering/exiting the cxl mode, with pnv_pci_set_tunnel_bar(). >>>> >>>> That should work with old skiboot (since we are re-writing the value >>>> already set) and new skiboot. >>> But doesn't that mean new skiboot can't boot any old kernel? That seems >>> undesirable. >> Yes, with new skiboot, all kernels will boot. > OK. > >> Capi mode tunnelled operations did not work until linux-4.17-rc1 (Apr >> 15, 2008). With new skiboot, kernels since linux-4.17-rc1 will loose > ^ > 1 > >> tunneled operations in capi mode, until this patch set is merged. > So it would be preferable if I put this patch into 4.17, so that the > 4.17 release works. Am I right? Yes. > >> Capi mode tunneled operations are not used in any IBM or partner GA >> products. The feature will be fully supported after this patch set and >> the libcxl PR https://github.com/ibm-capi/libcxl/pull/29 are merged. > OK. In general I ignore that sort of stuff because people also ignore it > when they're filing bugs against the kernel. So if it's in the tree we > want it to work (as much as possible), regardless of what's been GA'ed, > or is supported officially etc. > > cheers >