From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 449E0C43382 for ; Tue, 25 Sep 2018 21:15:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D045220896 for ; Tue, 25 Sep 2018 21:15:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="DDdOL4JE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D045220896 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-pci-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726323AbeIZDZY (ORCPT ); Tue, 25 Sep 2018 23:25:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:47392 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726281AbeIZDZX (ORCPT ); Tue, 25 Sep 2018 23:25:23 -0400 Received: from [10.80.45.152] (unknown [71.69.156.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 512F720877; Tue, 25 Sep 2018 21:15:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1537910154; bh=T+9fWDPyeM8YwENeKeLTSuDFdBNKMJyZrNWvrwVtiNM=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=DDdOL4JEkmJ07/ClqYEsHlcqm2dcknae4PVTj8L01abQY90xm+HLJOu5BkdIbafca E1LY9jcenSqVD1iJpC9ubtiwRUG38lUD2lRo/aOO0Ix2noTb9l6rnoJVR0WpgXyFzx egC1/h7De3LpDhNIQhiSeB2NrmgF13wtms16aMLM= Subject: Re: [PATCH v4 6/6] PCI: Expose reset type to users of pci_reset_bus() To: Bjorn Helgaas Cc: linux-pci@vger.kernel.org, alex.williamson@redhat.com, Bjorn Helgaas , Alexey Kardashevskiy , Peter Xu , "Gustavo A. R. Silva" References: <20180919163037.13497-1-okaya@kernel.org> <20180919163037.13497-7-okaya@kernel.org> <20180925205408.GD80129@bhelgaas-glaptop.roam.corp.google.com> From: Sinan Kaya Message-ID: Date: Tue, 25 Sep 2018 17:15:52 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180925205408.GD80129@bhelgaas-glaptop.roam.corp.google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 9/25/2018 4:54 PM, Bjorn Helgaas wrote: > On Wed, Sep 19, 2018 at 04:30:37PM +0000, Sinan Kaya wrote: >> Looking to have more control between the users of the API vs. what the API >> can do internally. The new reset_type tells the PCI core about the bounds >> of the request. >> >> Signed-off-by: Sinan Kaya >> --- >> drivers/pci/pci.c | 18 +++++++++++++++--- >> drivers/vfio/pci/vfio_pci.c | 6 ++++-- >> include/linux/pci.h | 2 +- >> 3 files changed, 20 insertions(+), 6 deletions(-) >> >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >> index b4f14419bd51..f11d29f32119 100644 >> --- a/drivers/pci/pci.c >> +++ b/drivers/pci/pci.c >> @@ -5232,13 +5232,25 @@ static int __pci_reset_bus(struct pci_bus *bus) >> /** >> * pci_reset_bus - Try to reset a PCI bus >> * @pdev: top level PCI device to reset via slot/bus >> + * @reset_type: resets to try >> * >> * Same as above except return -EAGAIN if the bus cannot be locked >> */ >> -int pci_reset_bus(struct pci_dev *pdev) >> +int pci_reset_bus(struct pci_dev *pdev, u32 reset_type) >> { >> - return (!pci_probe_reset_slot(pdev->slot)) ? >> - __pci_reset_slot(pdev->slot) : __pci_reset_bus(pdev->bus); >> + if (reset_type & PCI_RESET_LINK) { >> + return (!pci_probe_reset_slot(pdev->slot)) ? >> + __pci_reset_slot(pdev->slot) : >> + __pci_reset_bus(pdev->bus); >> + } >> + >> + if (reset_type & PCI_RESET_BUS) >> + return __pci_reset_bus(pdev->bus); >> + >> + if (reset_type & PCI_RESET_SLOT) >> + return __pci_reset_slot(pdev->slot); > > I don't understand this code. We have > > #define PCI_RESET_LINK (PCI_RESET_SLOT | PCI_RESET_BUS) > > so if either PCI_RESET_BUS or PCI_RESET_SLOT is set, we should take > the first "if" above, which always returns, and the last two should > never be reached. What am I missing? Yup, this is broken. I need to follow up with another patchset. I was trying to cover the case where user said, "I need a link reset. I don't care whether it is a slot reset or bus reset as long as we achieve a reset." That's when PCI_RESET_LINK is used. We expect most drivers to PCI_RESET_LINK if they are interested in a link reset and doesn't need to know about the hotplug capability of a particular slot. > >> + >> + return -EINVAL; >> } >> EXPORT_SYMBOL_GPL(pci_reset_bus); >> >> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c >> index fe7ada997c51..0e80c72b1eaa 100644 >> --- a/drivers/vfio/pci/vfio_pci.c >> +++ b/drivers/vfio/pci/vfio_pci.c >> @@ -1015,7 +1015,8 @@ static long vfio_pci_ioctl(void *device_data, >> &info, slot); >> if (!ret) >> /* User has access, do the reset */ >> - ret = pci_reset_bus(vdev->pdev); >> + ret = pci_reset_bus(vdev->pdev, >> + slot ? PCI_RESET_SLOT : PCI_RESET_BUS); > > This is the only place in the whole series where a caller uses > something other than PCI_RESET_ANY. Inquiring minds want to know why. > I'm sure it's the right thing to do, it's just that we'll need to know > how to choose in future cases. Use PCI_RESET_ANY for the existing behavior where you want one type of reset and don't care if it is PM/function/slot/bus/specific. Use PCI_RESET_LINK when you need link to retrain. Use PCI_RESET_SLOT when you know that this system is hotplug capable by calling probe functions. Use PCI_RESET_BUS when you know that this system is not hotplug capable and this endpoint will never be used in such a system. I can capture this into the commit message. > >> >> hot_reset_release: >> for (i--; i >= 0; i--) >> @@ -1390,7 +1391,8 @@ static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev) >> } >> >> if (needs_reset) >> - ret = pci_reset_bus(vdev->pdev); >> + ret = pci_reset_bus(vdev->pdev, >> + slot ? PCI_RESET_SLOT : PCI_RESET_BUS); >> >> put_devs: >> for (i = 0; i < devs.cur_index; i++) { >> diff --git a/include/linux/pci.h b/include/linux/pci.h >> index 4fdddcb85066..85f48e156753 100644 >> --- a/include/linux/pci.h >> +++ b/include/linux/pci.h >> @@ -1128,7 +1128,7 @@ int pci_reset_function_locked(struct pci_dev *dev, u32 reset_type); >> int pci_try_reset_function(struct pci_dev *dev, u32 reset_type); >> int pci_probe_reset_slot(struct pci_slot *slot); >> int pci_probe_reset_bus(struct pci_bus *bus); >> -int pci_reset_bus(struct pci_dev *dev); >> +int pci_reset_bus(struct pci_dev *dev, u32 reset_type); >> void pci_reset_secondary_bus(struct pci_dev *dev); >> void pcibios_reset_secondary_bus(struct pci_dev *dev); >> void pci_update_resource(struct pci_dev *dev, int resno); >> -- >> 2.18.0 >> >