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SubjectRe: [RFC PATCH v3] PCI/portdrv: Only disable Bus Master on kexec reboot and connected PCI devices
Hi, Tiezhu,

How do you test kexec? kexec -e or systemctl kexec? Or both?
P.S., Please also CC my gmail (chenhuacai@gmail.com) since lemote.com
has some communication problems.

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

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