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From:   Huacai Chen <chenhuacai@gmail.com>
Date:   Mon, 14 Sep 2020 17:46:19 +0800
Message-ID: <CAAhV-H5t1gCgBHtx=+Lu-9Fb7syJr0TsqdHc0qYQOfhXs-fJcQ@mail.gmail.com>
Subject: Re: [RFC PATCH v3] PCI/portdrv: Only disable Bus Master on kexec
 reboot and connected PCI devices
To:     Tiezhu Yang <yangtiezhu@loongson.cn>
Cc:     Bjorn Helgaas <bhelgaas@google.com>,
        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>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        Xuefeng Li <lixuefeng@loongson.cn>,
        zhouyanjie <zhouyanjie@wanyeetech.com>, git <git@xen0n.name>
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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=3D"root=3D/dev/sda2 console=3DttyS0,115200"
> kexec -e
So you haven't tested "systemctl kexec"?

Huacai
>
> > P.S., Please also CC my gmail (chenhuacai@gmail.com) since lemote.com
> > has some communication problems.
>
> OK, no problem.
>
> >
> > Huacai
> >
> >> =E9=99=88=E5=8D=8E=E6=89=8D=E6=B1=9F=E8=8B=8F=E8=88=AA=E5=A4=A9=E9=BE=
=99=E6=A2=A6=E4=BF=A1=E6=81=AF=E6=8A=80=E6=9C=AF=E6=9C=89=E9=99=90=E5=85=AC=
=E5=8F=B8/=E7=A0=94=E5=8F=91=E4=B8=AD=E5=BF=83/=E8=BD=AF=E4=BB=B6=E9=83=A8 =
  ------------------ Original ------------------From:  "Tiezhu Yang"<yangti=
ezhu@loongson.cn>;Date:  Mon, Sep 14, 2020 03:57 PMTo:  "Bjorn Helgaas"<bhe=
lgaas@google.com>; Cc:  "linux-pci"<linux-pci@vger.kernel.org>; "linux-kern=
el"<linux-kernel@vger.kernel.org>; "Rafael J. Wysocki"<rafael.j.wysocki@int=
el.com>; "Konstantin Khlebnikov"<khlebnikov@openvz.org>; "Khalid Aziz"<khal=
id.aziz@oracle.com>; "Vivek Goyal"<vgoyal@redhat.com>; "Lukas Wunner"<lukas=
@wunner.de>; "Oliver O'Halloran"<oohall@gmail.com>; "Huacai Chen"<chenhc@le=
mote.com>; "Jiaxun Yang"<jiaxun.yang@flygoat.com>; "Xuefeng Li"<lixuefeng@l=
oongson.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 &=3D ~PCI_COMMAND_MASTER;
> >>                  pci_write_config_word(dev, PCI_COMMAND, pci_command);
> >>          }
> >>
> >>          pcibios_disable_device(dev);
> >> }
> >>
> >> When remove "pci_command &=3D ~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: Disa=
ble
> >> 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 <=3D PCI_D3h=
ot))
> >>                  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/portdr=
v_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 *d=
ev)
> >>          }
> >>
> >>          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 =3D {
> >>
> >>          .probe          =3D pcie_portdrv_probe,
> >>          .remove         =3D pcie_portdrv_remove,
> >> -       .shutdown       =3D pcie_portdrv_remove,
> >> +       .shutdown       =3D pcie_portdrv_shutdown,
> >>
> >>          .err_handler    =3D &pcie_portdrv_err_handler,
> >>
> >> --
> >> 2.1.0
>