From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (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 3rgm9Q50LRzDql7 for ; Fri, 1 Jul 2016 16:05:29 +1000 (AEST) Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.11/8.16.0.11) with SMTP id u6160adM080980 for ; Fri, 1 Jul 2016 02:05:27 -0400 Received: from e23smtp07.au.ibm.com (e23smtp07.au.ibm.com [202.81.31.140]) by mx0a-001b2d01.pphosted.com with ESMTP id 23wbt332u2-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 01 Jul 2016 02:05:26 -0400 Received: from localhost by e23smtp07.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 1 Jul 2016 16:05:23 +1000 Received: from d23relay09.au.ibm.com (d23relay09.au.ibm.com [9.185.63.181]) by d23dlp01.au.ibm.com (Postfix) with ESMTP id 3F6462CE8046 for ; Fri, 1 Jul 2016 16:05:21 +1000 (EST) Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay09.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u6165LP422348026 for ; Fri, 1 Jul 2016 16:05:21 +1000 Received: from d23av02.au.ibm.com (localhost [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u6165KQF002366 for ; Fri, 1 Jul 2016 16:05:21 +1000 Date: Fri, 1 Jul 2016 16:05:19 +1000 From: Gavin Shan To: Yongji Xie Cc: Gavin Shan , nikunj@linux.vnet.ibm.com, zhong@linux.vnet.ibm.com, linux-doc@vger.kernel.org, aik@ozlabs.ru, linux-pci@vger.kernel.org, corbet@lwn.net, linux-kernel@vger.kernel.org, warrier@linux.vnet.ibm.com, alex.williamson@redhat.com, paulus@samba.org, bhelgaas@google.com, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v3 2/7] PCI: Ignore enforced alignment to VF BARs Reply-To: Gavin Shan References: <1467283993-3185-1-git-send-email-xyjxie@linux.vnet.ibm.com> <1467283993-3185-3-git-send-email-xyjxie@linux.vnet.ibm.com> <20160701003959.GB15147@gwshan> <21112bd7-d343-46b6-1df1-b20cc1c1b24e@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <21112bd7-d343-46b6-1df1-b20cc1c1b24e@linux.vnet.ibm.com> Message-Id: <20160701060519.GA8863@gwshan> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, Jul 01, 2016 at 01:27:17PM +0800, Yongji Xie wrote: >>On Thu, Jun 30, 2016 at 06:53:08PM +0800, Yongji Xie wrote: >>>VF BARs are read-only zeroes according to SRIOV spec, >>>the normal way(writing BARs) of allocating resources wouldn't >>>be applied to VFs. The VFs' resources would be allocated >>>when we enable SR-IOV capability. So we should not try to >>>reassign alignment after we enable VFs. It's meaningless >>>and will release the allocated resources which leads to a bug. >>> >>>Signed-off-by: Yongji Xie >>>--- >>>drivers/pci/pci.c | 4 ++++ >>>1 file changed, 4 insertions(+) >>> >>>diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >>>index be8f72c..6ae02de 100644 >>>--- a/drivers/pci/pci.c >>>+++ b/drivers/pci/pci.c >>>@@ -4822,6 +4822,10 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev) >>> resource_size_t align, size; >>> u16 command; >>> >>>+ /* We should never try to reassign VF's alignment */ >>>+ if (dev->is_virtfn) >>>+ return; >>>+ >>Yongji, I think it's correct to ignore VF's BARs. Another concern is: >>it's safe to apply alignment to PF's IOV BARs? Lets have an extreme >>example here: one PF has 16 VFs; each VF has only one 1KB. It means >>the only PF IOV BAR is 16KB. I don't see how it works after expanding >>it to 64KB which is the page size. It might be not a problem on PowerNV >>platform, but potentially a issue on x86? > >Seems like the alignment would not be applied to IOV BARs because >pci_reassigndev_resource_alignment() will be called before >sriov_init(). > Correct, thanks for the claim. I guess the alignment applied to PF IOV BARs should be ignored as well? Anyway, the IOV BARs are retireved from SRIOV capability. It deserves a comment if you plan to take the change. Actually, the comment here (for ignoring alignment to VF BARs) can be improved a bit as well, it'd better why the alignment cannot be applied. Thanks, Gavin