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From: Dave Young <dyoung@redhat.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: linux-pci@vger.kernel.org,
	Paul Menzel <pmenzel+linux-pci@molgen.mpg.de>,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	Sinan Kaya <okaya@codeaurora.org>, Lukas Wunner <lukas@wunner.de>,
	Eric Biederman <ebiederm@xmission.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Vivek Goyal <vgoyal@redhat.com>
Subject: Re: pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038 (issued 65284 msec ago)
Date: Sat, 28 Apr 2018 09:18:45 +0800	[thread overview]
Message-ID: <20180428011845.GC1675@dhcp-128-65.nay.redhat.com> (raw)
In-Reply-To: <20180428005620.GB1675@dhcp-128-65.nay.redhat.com>

On 04/28/18 at 08:56am, Dave Young wrote:
> On 04/27/18 at 04:12pm, Bjorn Helgaas wrote:
> > [+cc Eric, Vivek, kexec list]
> > 
> > On Fri, Apr 27, 2018 at 03:34:30PM -0400, Sinan Kaya wrote:
> > > On 4/27/2018 3:22 PM, Bjorn Helgaas wrote:
> > > > Sinan mooted the idea of using a "no-wait" path of sending the "don't
> > > > generate hotplug interrupts" command.  I think we should work on this
> > > > idea a little more.  If we're shutting down the whole system, I can't
> > > > believe there's much value in *anything* we do in the pciehp_remove()
> > > > path.
> > > > 
> > > > Maybe we should just get rid of pciehp_remove() (and probably
> > > > pcie_port_remove_service() and the other service driver remove methods)
> > > > completely.  That dates from when the service drivers could be modules that

Hmm, if it is the remove() method then kexec does not use it.  kexec use
the shutdown() method instead.  I missed this details when I replied.

> > > > could be potentially unloaded, but unloading them hasn't been possible for
> > > > years.
> > > 
> > > Shutdown path is also used for kexec. Leaving hotplug interrupts
> > > pending is dangerous for the newly loaded kernel as it leaves
> > > spurious interrupts during the new kernel boot.
> > > 
> > > I think we should always disable the hotplug interrupt on shutdown.
> > > We might think of not waiting for command-completion as a
> > > middle-ground or go to polling path instead of interrupts all the
> > > time.
> > 
> > Ah, I forgot about the kexec path.  The kexec path is used for
> > crashdump, too, so ideally the newly-loaded kernel would defend itself
> > when possible so it doesn't depend on the original kernel doing things
> > correctly.
> 
> It is true for kdump.  But kexec needs device shutdown.
> 
> > 
> > Seems like this question of whether to do things in the original
> > kernel or the kexec-ed kernel comes up periodically, but I can never
> > remember a definitive answer.  My initial reaction is that it'd be
> > nice if we didn't have to do *any* shutdown in the original kernel,
> > but I'm sure there are reasons that's not practical.
> 
> Devices sometimes assume it is in a good state initialized in firmware boot
> phase, so we need a shutdown in 1st kernel so that kexec kernel can boot
> correctly for those devices.  For kdump since kernel already panicked
> and it is not reliable so we do as less as we can in the 1st kernel
> crash path, but there are some special handling for kdump in various drivers
> to reset the devices in 2nd kernel, eg. when it see "reset_devices" kernel parameter.
> 
> > 
> > I copied Eric (kexec maintainer) and Vivek (contact listed in
> > Documentation/kdump/kdump.txt) in case they have suggestions or would
> > consider some sort of Documentation/ update.
> > 
> > Bjorn
> > 
> > _______________________________________________
> > kexec mailing list
> > kexec@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> 
> Thanks
> Dave
> 
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

  reply	other threads:[~2018-04-28  1:18 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-26 10:17 Paul Menzel
2018-04-27 19:22 ` Bjorn Helgaas
2018-04-27 19:34   ` Sinan Kaya
2018-04-27 21:12     ` Bjorn Helgaas
2018-04-28  0:56       ` Dave Young
2018-04-28  1:18         ` Dave Young [this message]
2018-04-28 13:03           ` okaya
2018-04-30 20:48             ` Sinan Kaya
2018-04-30 21:17               ` Bjorn Helgaas
2018-04-30 21:27                 ` Sinan Kaya
2018-04-30 21:38                   ` Lukas Wunner
2018-05-01 12:38                   ` Sinan Kaya
2018-05-01 12:59                     ` Marc Zyngier
2018-05-01 13:25                       ` Bjorn Helgaas
2018-05-01 16:31                         ` Marc Zyngier
2018-05-01 22:32                           ` Eric W. Biederman
2018-05-03  8:49   ` Paul Menzel
2018-05-04  2:45     ` Bjorn Helgaas
2018-05-04  6:37       ` okaya
2018-05-04 13:33         ` Bjorn Helgaas
2018-05-04 14:24           ` okaya
2018-05-06  9:35           ` Paul Menzel
2018-05-07 21:33           ` Bjorn Helgaas
2018-05-08  6:59             ` Paul Menzel
2018-05-08 12:34               ` Bjorn Helgaas
2018-05-08 13:22                 ` Paul Menzel
2018-05-09 11:41   ` Lukas Wunner
2018-05-09 12:57     ` Bjorn Helgaas
2018-05-09 13:16       ` Lukas Wunner

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