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Message-ID: <939d35d9-bbe7-3fef-7fc6-ff331d8f5010@loongson.cn>
Date: Mon, 14 Sep 2020 14:17:15 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Huacai Chen <chenhuacai@...il.com>,
Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Konstantin Khlebnikov <khlebnikov@...nvz.org>,
Khalid Aziz <khalid.aziz@...cle.com>,
Vivek Goyal <vgoyal@...hat.com>,
Lukas Wunner <lukas@...ner.de>, oohall <oohall@...il.com>,
"rafael.j.wysocki" <rafael.j.wysocki@...el.com>,
Xuefeng Li <lixuefeng@...ngson.cn>,
Jiaxun Yang <jiaxun.yang@...goat.com>,
linux-pci <linux-pci@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
zhouyanjie <zhouyanjie@...yeetech.com>, git <git@...0n.name>
Subject: Re: [RFC PATCH v2] PCI/portdrv: Only disable Bus Master on kexec
reboot and connected PCI devices
On 09/14/2020 12:31 PM, Huacai Chen wrote:
> Hi, Tiezhu
>
>> ------------------ Original ------------------
>> From: "Tiezhu Yang"<yangtiezhu@...ngson.cn>;
>> Date: Mon, Sep 14, 2020 04:29 AM
>> To: "Bjorn Helgaas"<bhelgaas@...gle.com>;
>> Cc: "Konstantin Khlebnikov"<khlebnikov@...nvz.org>; "Khalid Aziz"<khalid.aziz@...cle.com>; "Vivek Goyal"<vgoyal@...hat.com>; "Lukas Wunner"<lukas@...ner.de>; "oohall"<oohall@...il.com>; "rafael.j.wysocki"<rafael.j.wysocki@...el.com>; "Xuefeng Li"<lixuefeng@...ngson.cn>; "Huacai Chen"<chenhc@...ote.com>; "Jiaxun Yang"<jiaxun.yang@...goat.com>; "linux-pci"<linux-pci@...r.kernel.org>; "linux-kernel"<linux-kernel@...r.kernel.org>;
>> Subject: [RFC PATCH v2] PCI/portdrv: Only disable Bus Master on kexec reboot and connected PCI devices
>>
>>
>>
>> After commit 745be2e700cd ("PCIe: portdrv: call pci_disable_device
>> during remove") and commit cc27b735ad3a ("PCI/portdrv: Turn off PCIe
>> services during shutdown"), it also calls pci_disable_device() during
>> shutdown, this leads to shutdown or reboot failure occasionally due to
>> clear PCI_COMMAND_MASTER on the device in do_pci_disable_device().
>>
>> drivers/pci/pci.c
>> static void do_pci_disable_device(struct pci_dev *dev)
>> {
>> u16 pci_command;
>>
>> pci_read_config_word(dev, PCI_COMMAND, &pci_command);
>> if (pci_command & PCI_COMMAND_MASTER) {
>> pci_command &= ~PCI_COMMAND_MASTER;
>> pci_write_config_word(dev, PCI_COMMAND, pci_command);
>> }
>>
>> pcibios_disable_device(dev);
>> }
>>
>> When remove "pci_command &= ~PCI_COMMAND_MASTER;", it can work well.
>>
>> As Oliver O'Halloran said, no need to call pci_disable_device() when
>> actually shutting down, but we should call pci_disable_device() before
>> handing over to the new kernel on kexec reboot, so we can do some
>> condition checks which are similar with pci_device_shutdown(), this is
>> done by commit 4fc9bbf98fd6 ("PCI: Disable Bus Master only on kexec
>> reboot") and commit 6e0eda3c3898 ("PCI: Don't try to disable Bus Master
>> on disconnected PCI devices").
>>
>> drivers/pci/pci-driver.c
>> static void pci_device_shutdown(struct device *dev)
>> {
>> ...
>>
>> /*
>> * If this is a kexec reboot, turn off Bus Master bit on the
>> * device to tell it to not continue to do DMA. Don't touch
>> * devices in D3cold or unknown states.
>> * If it is not a kexec reboot, firmware will hit the PCI
>> * devices with big hammer and stop their DMA any way.
>> */
>> if (kexec_in_progress && (pci_dev->current_state <= PCI_D3hot))
>> pci_clear_master(pci_dev);
>> }
> Have you really tried kexec? Why do you think kexec can disable pci
> device successfully while normal reboot/poweroff cannot?
Yes, I test it on kexec reboot, it works well.
>
> Huacai
>> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
>> ---
>> drivers/pci/pcie/portdrv_core.c | 1 -
>> drivers/pci/pcie/portdrv_pci.c | 25 ++++++++++++++++++++++++-
>> 2 files changed, 24 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
>> index 50a9522..1991aca 100644
>> --- a/drivers/pci/pcie/portdrv_core.c
>> +++ b/drivers/pci/pcie/portdrv_core.c
>> @@ -491,7 +491,6 @@ void pcie_port_device_remove(struct pci_dev *dev)
>> {
>> device_for_each_child(&dev->dev, NULL, remove_iter);
>> pci_free_irq_vectors(dev);
>> - pci_disable_device(dev);
>> }
>>
>> /**
>> diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
>> index 3a3ce40..ce89a9e8 100644
>> --- a/drivers/pci/pcie/portdrv_pci.c
>> +++ b/drivers/pci/pcie/portdrv_pci.c
>> @@ -15,6 +15,7 @@
>> #include <linux/init.h>
>> #include <linux/aer.h>
>> #include <linux/dmi.h>
>> +#include <linux/kexec.h>
>>
>> #include "../pci.h"
>> #include "portdrv.h"
>> @@ -143,6 +144,28 @@ static void pcie_portdrv_remove(struct pci_dev *dev)
>> }
>>
>> pcie_port_device_remove(dev);
>> + pci_disable_device(dev);
>> +}
>> +
>> +static void pcie_portdrv_shutdown(struct pci_dev *dev)
>> +{
>> + if (pci_bridge_d3_possible(dev)) {
>> + pm_runtime_forbid(&dev->dev);
>> + pm_runtime_get_noresume(&dev->dev);
>> + pm_runtime_dont_use_autosuspend(&dev->dev);
>> + }
>> +
>> + pcie_port_device_remove(dev);
>> +
>> + /*
>> + * If this is a kexec reboot, turn off Bus Master bit on the
>> + * device to tell it to not continue to do DMA. Don't touch
>> + * devices in D3cold or unknown states.
>> + * If it is not a kexec reboot, firmware will hit the PCI
>> + * devices with big hammer and stop their DMA any way.
>> + */
>> + if (kexec_in_progress && (dev->current_state <= PCI_D3hot))
>> + pci_disable_device(dev);
>> }
>>
>> static pci_ers_result_t pcie_portdrv_error_detected(struct pci_dev *dev,
>> @@ -211,7 +234,7 @@ static void pcie_portdrv_err_resume(struct pci_dev *dev)
>>
>> .probe = pcie_portdrv_probe,
>> .remove = pcie_portdrv_remove,
>> - .shutdown = pcie_portdrv_remove,
>> + .shutdown = pcie_portdrv_shutdown,
>>
>> .err_handler = &pcie_portdrv_err_handler,
>>
>> --
>> 1.8.3.1
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