From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755477AbbFBGec (ORCPT ); Tue, 2 Jun 2015 02:34:32 -0400 Received: from mga02.intel.com ([134.134.136.20]:3857 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751748AbbFBGeZ (ORCPT ); Tue, 2 Jun 2015 02:34:25 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,538,1427785200"; d="scan'208";a="739215924" From: Jiang Liu To: Dave Jiang , Dan Williams , Vinod Koul , Jiang Liu , Jarkko Nikula Cc: David Woodhouse , Tony Luck , x86@kernel.org, linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org Subject: [RFC Patch V1] ioatdma: Ignore IOAT devices under hotplug-capable PCI host bridge Date: Tue, 2 Jun 2015 14:36:05 +0800 Message-Id: <1433226969-8748-1-git-send-email-jiang.liu@linux.intel.com> X-Mailer: git-send-email 1.7.10.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The dmaengine core assumes that async DMA devices will only be removed when they not used anymore, or it assumes dma_async_device_unregister() will only be called by dma driver exit routines. But this assumption is not true for the IOAT driver, which calls dma_async_device_unregister() from ioat_remove(). So current IOAT driver doesn't support device hot-removal because it may cause system crash to hot-remove an inuse IOAT device. To support CPU socket hot-removal, all PCI devices, including IOAT devices embedded in the socket, will be hot-removed. The idea solution is to enhance the dmaengine core and IOAT driver to support hot-removal, but that's too hard. This patch implements a hack to disable IOAT devices under hotplug-capable CPU socket so it won't break socket hot-removal. Signed-off-by: Jiang Liu --- drivers/dma/ioat/pci.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/drivers/dma/ioat/pci.c b/drivers/dma/ioat/pci.c index 76f0dc688a19..3b8c9b03f4b3 100644 --- a/drivers/dma/ioat/pci.c +++ b/drivers/dma/ioat/pci.c @@ -27,6 +27,7 @@ #include #include #include +#include #include "dma.h" #include "dma_v2.h" #include "registers.h" @@ -148,6 +149,34 @@ alloc_ioatdma(struct pci_dev *pdev, void __iomem *iobase) return d; } +/* + * The dmaengine core assumes that async DMA devices will only be removed + * when they not used anymore, or it assumes dma_async_device_unregister() + * will only be called by dma driver exit routines. But this assumption is + * not true for the IOAT driver, which calls dma_async_device_unregister() + * from ioat_remove(). So current IOAT driver doesn't support device + * hot-removal because it may cause system crash to hot-remove inuse IOAT + * devices. + * + * This is a hack to disable IOAT devices under ejectable PCI host bridge + * so it won't break PCI host bridge hot-removal. + */ +static bool ioat_pci_has_ejectable_acpi_ancestor(struct pci_dev *pdev) +{ +#ifdef CONFIG_ACPI + struct pci_bus *bus = pdev->bus; + struct acpi_device *adev; + + while (bus->parent) + bus = bus->parent; + for (adev = ACPI_COMPANION(bus->bridge); adev; adev = adev->parent) + if (adev->flags.ejectable) + return true; +#endif + + return false; +} + static int ioat_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id) { void __iomem * const *iomap; @@ -155,6 +184,11 @@ static int ioat_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id) struct ioatdma_device *device; int err; + if (ioat_pci_has_ejectable_acpi_ancestor(pdev)) { + dev_dbg(&pdev->dev, "ignore ejectable IOAT device.\n"); + return -ENODEV; + } + err = pcim_enable_device(pdev); if (err) return err; -- 1.7.10.4