Re: [RFC PATCH v2] PCI/portdrv: Only disable Bus Master on kexec reboot and connected PCI devices

[Tiezhu Yang]

On 09/14/2020 12:31 PM, Huacai Chen wrote:
> Hi, Tiezhu
>
> > ------------------ Original ------------------
> > From:  "Tiezhu Yang"<yangtiezhu@xxxxxxxxxxx>;
> > Date:  Mon, Sep 14, 2020 04:29 AM
> > To:  "Bjorn Helgaas"<bhelgaas@xxxxxxxxxx>;
> > Cc:  "Konstantin Khlebnikov"<khlebnikov@xxxxxxxxxx>; "Khalid Aziz"<khalid.aziz@xxxxxxxxxx>; "Vivek Goyal"<vgoyal@xxxxxxxxxx>; "Lukas Wunner"<lukas@xxxxxxxxx>; "oohall"<oohall@xxxxxxxxx>; "rafael.j.wysocki"<rafael.j.wysocki@xxxxxxxxx>; "Xuefeng Li"<lixuefeng@xxxxxxxxxxx>; "Huacai Chen"<chenhc@xxxxxxxxxx>; "Jiaxun Yang"<jiaxun.yang@xxxxxxxxxxx>; "linux-pci"<linux-pci@xxxxxxxxxxxxxxx>; "linux-kernel"<linux-kernel@xxxxxxxxxxxxxxx>;
> > 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@xxxxxxxxxxx>
> > ---
> >   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