From patchwork Thu Jan 21 22:13:29 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Sean O. Stalley" X-Patchwork-Id: 571360 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id A2C1014031B for ; Fri, 22 Jan 2016 09:17:17 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750912AbcAUWRQ (ORCPT ); Thu, 21 Jan 2016 17:17:16 -0500 Received: from mga02.intel.com ([134.134.136.20]:8775 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750838AbcAUWRQ (ORCPT ); Thu, 21 Jan 2016 17:17:16 -0500 Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga101.jf.intel.com with ESMTP; 21 Jan 2016 14:17:17 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,327,1449561600"; d="scan'208";a="638077422" Received: from dev.jf.intel.com ([134.134.147.14]) by FMSMGA003.fm.intel.com with ESMTP; 21 Jan 2016 14:17:15 -0800 From: "Sean O. Stalley" To: linux-pci@vger.kernel.org, mj@ucw.cz, bhelgaas@google.com, alex.williamson@redhat.com Cc: sean.stalley@intel.com, david.daney@cavium.com Subject: [PATCH 1/2] pci: Identify Enhanced Allocation (EA) BAR Equivalent resources Date: Thu, 21 Jan 2016 14:13:29 -0800 Message-Id: <1453414410-27072-2-git-send-email-sean.stalley@intel.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1453414410-27072-1-git-send-email-sean.stalley@intel.com> References: <1453414410-27072-1-git-send-email-sean.stalley@intel.com> Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org From: Alex Williamson We've done a pretty good job of abstracting EA from drivers, but there are some properties of BAR Equivalent resources that don't really jive with traditional PCI BARs. In particular, natural alignment is only encouraged, not required. Why does this matter? There are drivers like vfio-pci that will happily gobble up the EA abstraction that's been implemented and expose a device using EA to userspace as if those resources are traditional BARs. Pretty cool. The vfio API is bus agnostic, so it doesn't care about alignment. The problem comes with PCI config space emulation where we don't let userspace manipulate the BAR value, but we do emulate BAR sizing. The abstraction kind of falls apart if userspace gets garbage when they try to size what appears to be a traditional BAR, but is actually a BAR equivalent. We could simply round up the size in vfio to make it naturally aligned, but then we're imposing artificial sizes to the user and we have the discontinuity that BAR size emulation and vfio region size reporting don't agree on the size. I think what we want to do is expose EA to the user, reporting traditional BARs with BEIs as zero-sized and providing additional regions for the user to access each EA region, whether it has a BEI or not. To facilitate that, a flag indicating whether a PCI resource is a traditional BAR or BAR equivalent seems much nicer than attempting to size the BAR ourselves or deducing it through the EA capability. Thoughts? Signed-off-by: Alex Williamson --- drivers/pci/pci.c | 2 +- include/linux/ioport.h | 2 ++ 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index d1a7105..8ff678c 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -2229,7 +2229,7 @@ void pci_pm_init(struct pci_dev *dev) static unsigned long pci_ea_flags(struct pci_dev *dev, u8 prop) { - unsigned long flags = IORESOURCE_PCI_FIXED; + unsigned long flags = IORESOURCE_PCI_FIXED | IORESOURCE_PCI_EA_BEI; switch (prop) { case PCI_EA_P_MEM: diff --git a/include/linux/ioport.h b/include/linux/ioport.h index 24bea08..5acc194 100644 --- a/include/linux/ioport.h +++ b/include/linux/ioport.h @@ -105,6 +105,8 @@ struct resource { /* PCI control bits. Shares IORESOURCE_BITS with above PCI ROM. */ #define IORESOURCE_PCI_FIXED (1<<4) /* Do not move resource */ +/* PCI Enhanced Allocation defined BAR equivalent resource */ +#define IORESOURCE_PCI_EA_BEI (1<<5) /* helpers to define resources */ #define DEFINE_RES_NAMED(_start, _size, _name, _flags) \