linux-kernel - Re: [PATCH] PCI/portdrv: do not disable device on remove()

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Date:   Tue, 22 May 2018 12:55:53 -0700
From:   Ryan Finnie <ryan@...nie.org>
To:     Sinan Kaya <okaya@...eaurora.org>, linux-pci@...r.kernel.org,
        timur@...eaurora.org
Cc:     linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, stable@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Frederick Lawler <fred@...dlawl.com>,
        Dongdong Liu <liudongdong3@...wei.com>,
        Gabriele Paoloni <gabriele.paoloni@...wei.com>,
        Keith Busch <keith.busch@...el.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI/portdrv: do not disable device on remove()

On 05/22/2018 10:58 AM, Sinan Kaya wrote:
> 'Commit cc27b735ad3a ("PCI/portdrv: Turn off PCIe services during
> shutdown")' has been added to kernel to shutdown pending PCIe port
> service interrupts during reboot so that a newly started kexec kernel
> wouldn't observe pending interrupts.
> 
> pcie_port_device_remove() is disabling the root port and switches by
> calling pci_disable_device() after all PCIe service drivers are shutdown.
> 
> pci_disable_device() has a much wider impact then port service itself and
> it prevents all inbound transactions to reach to the system and impacts
> the entire PCI traffic behind the bridge.
> 
> Issue is that pcie_port_device_remove() doesn't maintain any coordination
> with the rest of the PCI device drivers in the system before clearing the
> bus master bit.
> 
> This has been found to cause crashes on HP DL360 Gen9 machines during
> reboot. Besides, kexec is already clearing the bus master bit in
> pci_device_shutdown() after all PCI drivers are removed.

FAOD, this problem has been observed on both DL360 Gen9 and DL380 Gen9,
in both EFI and legacy modes.  I suspect all Gen9 models with the P89
firmware base.

> Just remove the extra clear here.

Thank you!  Fix tested on:

- DL360 Gen9
- DL380 Gen9
- DL380 Gen10 (confirmed no regression)
- DL380 G7 (confirmed no regression)

> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=199779
> Fixes: cc27b735ad3a ("PCI/portdrv: Turn off PCIe services during shutdown")
> Cc: stable@...r.kernel.org
> Reported-by: Ryan Finnie <ryan@...nie.org>

Tested-by: Ryan Finnie <ryan@...nie.org>