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Message-ID: <20200222165631.GA213225@google.com>
Date: Sat, 22 Feb 2020 10:56:31 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Kairui Song <kasong@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
kexec@...ts.infradead.org, Jerry Hoemann <jerry.hoemann@....com>,
Baoquan He <bhe@...hat.com>,
Khalid Aziz <khalid@...ehiking.org>,
Deepa Dinamani <deepa.kernel@...il.com>,
Randy Wright <rwright@....com>, Dave Young <dyoung@...hat.com>,
Myron Stowe <myron.stowe@...hat.com>
Subject: Re: [RFC PATCH] PCI, kdump: Clear bus master bit upon shutdown in
kdump kernel
[+cc Khalid, Deepa, Randy, Dave, Myron]
On Thu, Dec 26, 2019 at 03:21:18AM +0800, Kairui Song wrote:
> There are reports about kdump hang upon reboot on some HPE machines,
> kernel hanged when trying to shutdown a PCIe port, an uncorrectable
> error occurred and crashed the system.
Did we ever make progress on this? This definitely sounds like a
problem that needs to be fixed, but I don't see a resolution here.
> On the machine I can reproduce this issue, part of the topology
> looks like this:
>
> [0000:00]-+-00.0 Intel Corporation Xeon E7 v3/Xeon E5 v3/Core i7 DMI2
> +-01.0-[02]--
> +-01.1-[05]--
> +-02.0-[06]--+-00.0 Emulex Corporation OneConnect NIC (Skyhawk)
> | +-00.1 Emulex Corporation OneConnect NIC (Skyhawk)
> | +-00.2 Emulex Corporation OneConnect NIC (Skyhawk)
> | +-00.3 Emulex Corporation OneConnect NIC (Skyhawk)
> | +-00.4 Emulex Corporation OneConnect NIC (Skyhawk)
> | +-00.5 Emulex Corporation OneConnect NIC (Skyhawk)
> | +-00.6 Emulex Corporation OneConnect NIC (Skyhawk)
> | \-00.7 Emulex Corporation OneConnect NIC (Skyhawk)
> +-02.1-[0f]--
> +-02.2-[07]----00.0 Hewlett-Packard Company Smart Array Gen9 Controllers
>
> When shuting down PCIe port 0000:00:02.2 or 0000:00:02.0, the machine
> will hang, depend on which device is reinitialized in kdump kernel.
>
> If force remove unused device then trigger kdump, the problem will never
> happen:
>
> echo 1 > /sys/bus/pci/devices/0000\:00\:02.2/0000\:07\:00.0/remove
> echo c > /proc/sysrq-trigger
>
> ... Kdump save vmcore through network, the NIC get reinitialized and
> hpsa is untouched. Then reboot with no problem. (If hpsa is used
> instead, shutdown the NIC in first kernel will help)
>
> The cause is that some devices are enabled by the first kernel, but it
> don't have the chance to shutdown the device, and kdump kernel is not
> aware of it, unless it reinitialize the device.
>
> Upon reboot, kdump kernel will skip downstream device shutdown and
> clears its bridge's master bit directly. The downstream device could
> error out as it can still send requests but upstream refuses it.
>
> So for kdump, let kernel read the correct hardware power state on boot,
> and always clear the bus master bit of PCI device upon shutdown if the
> device is on. PCIe port driver will always shutdown all downstream
> devices first, so this should ensure all downstream devices have bus
> master bit off before clearing the bridge's bus master bit.
>
> Signed-off-by: Kairui Song <kasong@...hat.com>
> ---
> drivers/pci/pci-driver.c | 11 ++++++++---
> drivers/pci/quirks.c | 20 ++++++++++++++++++++
> 2 files changed, 28 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index 0454ca0e4e3f..84a7fd643b4d 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -18,6 +18,7 @@
> #include <linux/kexec.h>
> #include <linux/of_device.h>
> #include <linux/acpi.h>
> +#include <linux/crash_dump.h>
> #include "pci.h"
> #include "pcie/portdrv.h"
>
> @@ -488,10 +489,14 @@ 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 this is kdump kernel, also turn off Bus Master, the device
> + * could be activated by previous crashed kernel and may block
> + * it's upstream from shutting down.
> + * Else, 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))
> + if ((kexec_in_progress || is_kdump_kernel()) &&
> + pci_dev->current_state <= PCI_D3hot)
> pci_clear_master(pci_dev);
> }
>
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 4937a088d7d8..c65d11ab3939 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -28,6 +28,7 @@
> #include <linux/platform_data/x86/apple.h>
> #include <linux/pm_runtime.h>
> #include <linux/switchtec.h>
> +#include <linux/crash_dump.h>
> #include <asm/dma.h> /* isa_dma_bridge_buggy */
> #include "pci.h"
>
> @@ -192,6 +193,25 @@ static int __init pci_apply_final_quirks(void)
> }
> fs_initcall_sync(pci_apply_final_quirks);
>
> +/*
> + * Read the device state even if it's not enabled. The device could be
> + * activated by previous crashed kernel, this will read and correct the
> + * cached state.
> + */
> +static void quirk_read_pm_state_in_kdump(struct pci_dev *dev)
> +{
> + u16 pmcsr;
> +
> + if (!is_kdump_kernel())
> + return;
> +
> + if (dev->pm_cap) {
> + pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
> + dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
> + }
> +}
> +DECLARE_PCI_FIXUP_FINAL(PCI_ANY_ID, PCI_ANY_ID, quirk_read_pm_state_in_kdump);
> +
> /*
> * Decoding should be disabled for a PCI device during BAR sizing to avoid
> * conflict. But doing so may cause problems on host bridge and perhaps other
> --
> 2.24.1
>
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