Re: [RFC PATCH v3] PCI/portdrv: Only disable Bus Master on kexec reboot and connected PCI devices

[Tiezhu Yang <yangtiezhu@loongson.cn>]

On 09/14/2020 05:46 PM, Huacai Chen wrote:
> Hi, Tiezhu,
>
> On Mon, Sep 14, 2020 at 5:30 PM Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
>> On 09/14/2020 04:52 PM, Huacai Chen wrote:
>>> Hi, Tiezhu,
>>>
>>> How do you test kexec? kexec -e or systemctl kexec? Or both?
>> kexec -l vmlinux --append="root=/dev/sda2 console=ttyS0,115200"
>> kexec -e
> So you haven't tested "systemctl kexec"?

Yes, the distro I used is Loongnix which has not kexec service now.
Is there any problem when use systemctl kexec? If you have more details,
please let me know.

>
> Huacai
>>> P.S., Please also CC my gmail (chenhuacai@gmail.com) since lemote.com
>>> has some communication problems.
>> OK, no problem.
>>
>>> Huacai
>>>
>>>> 陈华才江苏航天龙梦信息技术有限公司/研发中心/软件部   ------------------ Original ------------------From:  "Tiezhu Yang"<yangtiezhu@loongson.cn>;Date:  Mon, Sep 14, 2020 03:57 PMTo:  "Bjorn Helgaas"<bhelgaas@google.com>; Cc:  "linux-pci"<linux-pci@vger.kernel.org>; "linux-kernel"<linux-kernel@vger.kernel.org>; "Rafael J. Wysocki"<rafael.j.wysocki@intel.com>; "Konstantin Khlebnikov"<khlebnikov@openvz.org>; "Khalid Aziz"<khalid.aziz@oracle.com>; "Vivek Goyal"<vgoyal@redhat.com>; "Lukas Wunner"<lukas@wunner.de>; "Oliver O'Halloran"<oohall@gmail.com>; "Huacai Chen"<chenhc@lemote.com>; "Jiaxun Yang"<jiaxun.yang@flygoat.com>; "Xuefeng Li"<lixuefeng@loongson.cn>; Subject:  [RFC PATCH v3] 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 when
>>>> shutdown or reboot.
>>>>
>>>> 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 already executed afterwards by the function
>>>> 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 (drv && drv->shutdown)
>>>>                   drv->shutdown(pci_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);
>>>> }
>>>>
>>>> [   36.159446] Call Trace:
>>>> [   36.241688] [<ffffffff80211434>] show_stack+0x9c/0x130
>>>> [   36.326619] [<ffffffff80661b70>] dump_stack+0xb0/0xf0
>>>> [   36.410403] [<ffffffff806a8240>] pcie_portdrv_shutdown+0x18/0x78
>>>> [   36.495302] [<ffffffff8069c6b4>] pci_device_shutdown+0x44/0x90
>>>> [   36.580027] [<ffffffff807aac90>] device_shutdown+0x130/0x290
>>>> [   36.664486] [<ffffffff80265448>] kernel_power_off+0x38/0x80
>>>> [   36.748272] [<ffffffff80265634>] __do_sys_reboot+0x1a4/0x258
>>>> [   36.831985] [<ffffffff80218b90>] syscall_common+0x34/0x58
>>>>
>>>> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
>>>> ---
>>>>    drivers/pci/pcie/portdrv_core.c |  1 -
>>>>    drivers/pci/pcie/portdrv_pci.c  | 14 +++++++++++++-
>>>>    2 files changed, 13 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..cab37a8 100644
>>>> --- a/drivers/pci/pcie/portdrv_pci.c
>>>> +++ b/drivers/pci/pcie/portdrv_pci.c
>>>> @@ -143,6 +143,18 @@ 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);
>>>>    }
>>>>
>>>>    static pci_ers_result_t pcie_portdrv_error_detected(struct pci_dev *dev,
>>>> @@ -211,7 +223,7 @@ static struct pci_driver pcie_portdriver = {
>>>>
>>>>           .probe          = pcie_portdrv_probe,
>>>>           .remove         = pcie_portdrv_remove,
>>>> -       .shutdown       = pcie_portdrv_remove,
>>>> +       .shutdown       = pcie_portdrv_shutdown,
>>>>
>>>>           .err_handler    = &pcie_portdrv_err_handler,
>>>>
>>>> --
>>>> 2.1.0