From: Bjorn Helgaas <helgaas@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Guilherme G. Piccoli" <gpiccoli@canonical.com>,
linux-pci@vger.kernel.org, kexec@lists.infradead.org,
x86@kernel.org, linux-kernel@vger.kernel.org,
bhelgaas@google.com, dyoung@redhat.com, bhe@redhat.com,
vgoyal@redhat.com, mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
andi@firstfloor.org, lukas@wunner.de, okaya@kernel.org,
kernelfans@gmail.com, ddstreet@canonical.com,
gavin.guo@canonical.com, jay.vosburgh@canonical.com,
kernel@gpiccoli.net, shan.gavin@linux.alibaba.com,
Eric Biederman <ebiederm@xmission.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: [PATCH 1/3] x86/quirks: Scan all busses for early PCI quirks
Date: Sat, 14 Nov 2020 15:22:15 -0600 [thread overview]
Message-ID: <20201114212215.GA1194074@bjorn-Precision-5520> (raw)
In-Reply-To: <87h7prac67.fsf@nanos.tec.linutronix.de>
[+cc Rafael for question about ACPI method for PCI host bridge reset]
On Sat, Nov 14, 2020 at 09:58:08PM +0100, Thomas Gleixner wrote:
> On Sat, Nov 14 2020 at 14:39, Bjorn Helgaas wrote:
> > On Sat, Nov 14, 2020 at 12:40:10AM +0100, Thomas Gleixner wrote:
> >> On Sat, Nov 14 2020 at 00:31, Thomas Gleixner wrote:
> >> > On Fri, Nov 13 2020 at 10:46, Bjorn Helgaas wrote:
> >> >> pci_device_shutdown() still clears the Bus Master Enable bit if we're
> >> >> doing a kexec and the device is in D0-D3hot, which should also disable
> >> >> MSI/MSI-X. Why doesn't this solve the problem? Is this because the
> >> >> device causing the storm was in PCI_UNKNOWN state?
> >> >
> >> > That's indeed a really good question.
> >>
> >> So we do that on kexec, but is that true when starting a kdump kernel
> >> from a kernel crash? I doubt it.
> >
> > Ah, right, I bet that's it, thanks. The kdump path is basically this:
> >
> > crash_kexec
> > machine_kexec
> >
> > while the usual kexec path is:
> >
> > kernel_kexec
> > kernel_restart_prepare
> > device_shutdown
> > while (!list_empty(&devices_kset->list))
> > dev->bus->shutdown
> > pci_device_shutdown # pci_bus_type.shutdown
> > machine_kexec
> >
> > So maybe we need to explore doing some or all of device_shutdown() in
> > the crash_kexec() path as well as in the kernel_kexec() path.
>
> The problem is that if the machine crashed anything you try to attempt
> before starting the crash kernel is reducing the chance that the crash
> kernel actually starts.
Right.
> Is there something at the root bridge level which allows to tell the
> underlying busses to shut up, reset or go into a defined state? That
> might avoid chasing lists which might be already unreliable.
Maybe we need some kind of crash_device_shutdown() that does the
minimal thing to protect the kdump kernel from devices.
The programming model for conventional PCI host bridges and PCIe Root
Complexes is device-specific since they're outside the PCI domain.
There probably *are* ways to do those things, but you would need a
native host bridge driver or something like an ACPI method. I'm not
aware of an ACPI way to do this, but I added Rafael in case he is.
A crash_device_shutdown() could do something at the host bridge level
if that's possible, or reset/disable bus mastering/disable MSI/etc on
individual PCI devices if necessary.
Bjorn
next prev parent reply other threads:[~2020-11-14 21:22 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-18 18:37 [PATCH 1/3] x86/quirks: Scan all busses for early PCI quirks Guilherme G. Piccoli
2018-10-18 18:37 ` [PATCH 2/3] x86/PCI: Export find_cap() to be used in early PCI code Guilherme G. Piccoli
2018-10-18 18:37 ` [PATCH 3/3] x86/quirks: Add parameter to clear MSIs early on boot Guilherme G. Piccoli
2018-10-18 20:08 ` Sinan Kaya
2018-10-18 20:13 ` Guilherme G. Piccoli
2018-10-18 20:30 ` Sinan Kaya
2018-10-22 19:44 ` Guilherme G. Piccoli
2018-10-18 22:15 ` [PATCH 1/3] x86/quirks: Scan all busses for early PCI quirks Bjorn Helgaas
2018-10-22 20:35 ` Guilherme G. Piccoli
2018-10-23 17:03 ` Bjorn Helgaas
2020-11-06 13:14 ` Guilherme G. Piccoli
2020-11-13 16:46 ` Bjorn Helgaas
2020-11-13 23:31 ` Thomas Gleixner
2020-11-13 23:40 ` Thomas Gleixner
2020-11-14 20:39 ` Bjorn Helgaas
2020-11-14 20:58 ` Thomas Gleixner
2020-11-14 21:22 ` Bjorn Helgaas [this message]
2020-11-15 14:05 ` Eric W. Biederman
2020-11-15 14:29 ` Eric W. Biederman
2020-11-15 15:11 ` Thomas Gleixner
2020-11-15 17:01 ` Lukas Wunner
2020-11-15 19:18 ` Thomas Gleixner
2020-11-15 20:46 ` Eric W. Biederman
2020-11-16 20:31 ` Guilherme G. Piccoli
2020-11-16 21:45 ` Eric W. Biederman
2020-11-16 21:49 ` Guilherme Piccoli
2020-11-17 0:19 ` Bjorn Helgaas
2020-11-17 1:06 ` Eric W. Biederman
2020-11-17 9:53 ` Thomas Gleixner
2020-11-17 12:19 ` David Woodhouse
2020-11-17 19:34 ` Thomas Gleixner
2020-11-17 22:25 ` Eric W. Biederman
2020-11-17 12:04 ` Guilherme Piccoli
2020-11-18 21:05 ` Bjorn Helgaas
2020-11-18 22:36 ` Guilherme Piccoli
2020-11-30 20:20 ` Bjorn Helgaas
2020-12-14 18:32 ` Guilherme Piccoli
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