From: "Guilherme G. Piccoli" <gpiccoli@canonical.com>
To: Sinan Kaya <okaya@kernel.org>,
linux-pci@vger.kernel.org, kexec@lists.infradead.org,
x86@kernel.org
Cc: linux-kernel@vger.kernel.org, bhelgaas@google.com,
dyoung@redhat.com, bhe@redhat.com, vgoyal@redhat.com,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, andi@firstfloor.org, lukas@wunner.de,
billy.olsen@canonical.com, cascardo@canonical.com,
ddstreet@canonical.com, fabiomirmar@canonical.com,
gavin.guo@canonical.com, jay.vosburgh@canonical.com,
kernel@gpiccoli.net, mfo@canonical.com,
shan.gavin@linux.alibaba.com
Subject: Re: [PATCH 3/3] x86/quirks: Add parameter to clear MSIs early on boot
Date: Mon, 22 Oct 2018 16:44:04 -0300 [thread overview]
Message-ID: <92dc24c9-0963-e894-66fe-ad74bdbc0ac3@canonical.com> (raw)
In-Reply-To: <50d84d48-eebf-ed91-8148-be727f76883f@kernel.org>
On 18/10/2018 17:30, Sinan Kaya wrote:
>
> AFAIK, all shutdown (not remove) routines are called before launching
> the next
> kernel even in crash scenario. It is not safe to start the new kernel while
> hardware is doing a DMA to the system memory and triggering interrupts.
Hi Sinan,
I agree with you, it's definitely not safe to start a new kernel with
in-flight DMA transactions, but in the crash scenario I think the
rationale was that running kernel is broken so it's even more unreliable
to try gracefully shutdown the devices than hope-for-the-best and start
the kdump kernel right away heheh
Fact is that the shutdown handlers are not called in the crash scenario.
They come from device_shutdown(), the code paths are as follow:
Regular kexec flow:
syscall_reboot()
kernel_kexec()
kernel_restart_prepare()
device_shutdown()
machine_kexec()
Although if CONFIG_KEXEC_JUMP is set, it doesn't call device_shutdown()
either.
Crash kexec flow:
__crash_kexec()
machine_kexec()
There are some entry points to __crash_kexec(), like panic() or die() in
x86, for example.
To validate this, one can load a kernel with "initcall_debug" parameter,
and performs a kexec - if the shutdown handlers are called, there's a
dev_info() call that shows a message per device.
> Shutdown routine in PCI core used to disable MSI/MSI-x on behalf of all
> endpoints but it was later decided that this is the responsibility of the
> endpoint driver.
>
This may be a good idea, using the pci layer to disable MSIs in the
quiesce path of the broken kernel. I'll follow-up this discussion in
Bjorn's reply.
Thanks,
Guilherme
next prev parent reply other threads:[~2018-10-22 19:44 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 [this message]
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
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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