From patchwork Mon Apr 17 21:36:46 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bjorn Helgaas X-Patchwork-Id: 9684569 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id C4D24600F6 for ; Mon, 17 Apr 2017 21:36:51 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B3DDD25223 for ; Mon, 17 Apr 2017 21:36:51 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A7D0528236; Mon, 17 Apr 2017 21:36:51 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5AB2B25223 for ; Mon, 17 Apr 2017 21:36:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753250AbdDQVgu (ORCPT ); Mon, 17 Apr 2017 17:36:50 -0400 Received: from mail.kernel.org ([198.145.29.136]:40176 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751852AbdDQVgu (ORCPT ); Mon, 17 Apr 2017 17:36:50 -0400 Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id BD81A2021F; Mon, 17 Apr 2017 21:36:48 +0000 (UTC) Received: from localhost (unknown [69.55.156.165]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AF1E920220; Mon, 17 Apr 2017 21:36:47 +0000 (UTC) Subject: [PATCH v11 3/7] PCI: Add pcibios_default_alignment() for arch-specific alignment control From: Bjorn Helgaas To: Yongji Xie Cc: zhong@linux.vnet.ibm.com, Alexey Kardashevskiy , linux-pci@vger.kernel.org, Gavin Shan , Alex Williamson , Paul Mackerras , Michael Ellerman , Benjamin Herrenschmidt , linuxppc-dev@lists.ozlabs.org Date: Mon, 17 Apr 2017 16:36:46 -0500 Message-ID: <20170417213646.21092.24262.stgit@bhelgaas-glaptop.roam.corp.google.com> In-Reply-To: <20170417212705.21092.90222.stgit@bhelgaas-glaptop.roam.corp.google.com> References: <20170417212705.21092.90222.stgit@bhelgaas-glaptop.roam.corp.google.com> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-Virus-Scanned: ClamAV using ClamSMTP Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Yongji Xie When VFIO passes through a PCI device to a guest, it does not allow the guest to mmap BARs that are smaller than PAGE_SIZE unless it can reserve the rest of the page (see vfio_pci_probe_mmaps()). This is because a page might contain several small BARs for unrelated devices and a guest should not be able to access all of them. VFIO emulates guest accesses to non-mappable BARs, which is functional but slow. On systems with large page sizes, e.g., PowerNV with 64K pages, BARs are more likely to share a page and performance is more likely to be a problem. Add a weak function to set default alignment for all PCI devices. An arch can override it to force the PCI core to place memory BARs on their own pages. Signed-off-by: Yongji Xie Signed-off-by: Bjorn Helgaas --- drivers/pci/pci.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 679af2a253ad..a2d1f144c94f 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4947,6 +4947,11 @@ void pci_ignore_hotplug(struct pci_dev *dev) } EXPORT_SYMBOL_GPL(pci_ignore_hotplug); +resource_size_t __weak pcibios_default_alignment(struct pci_dev *dev) +{ + return 0; +} + #define RESOURCE_ALIGNMENT_PARAM_SIZE COMMAND_LINE_SIZE static char resource_alignment_param[RESOURCE_ALIGNMENT_PARAM_SIZE] = {0}; static DEFINE_SPINLOCK(resource_alignment_lock); @@ -4962,14 +4967,15 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev) { int seg, bus, slot, func, align_order, count; unsigned short vendor, device, subsystem_vendor, subsystem_device; - resource_size_t align = 0; + resource_size_t align = pcibios_default_alignment(dev); char *p; spin_lock(&resource_alignment_lock); p = resource_alignment_param; - if (!*p) + if (!*p && !align) goto out; if (pci_has_flag(PCI_PROBE_ONLY)) { + align = 0; pr_info_once("PCI: Ignoring requested alignments (PCI_PROBE_ONLY)\n"); goto out; }