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From: Vivek Goyal <vgoyal@redhat.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Matthew Garrett <matthew.garrett@nebula.com>,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [Q] Why does kexec use device_shutdown rather than ubind them
Date: Fri, 17 Jan 2014 09:13:27 -0500	[thread overview]
Message-ID: <20140117141327.GC24394@redhat.com> (raw)
In-Reply-To: <1389938353.7406.22.camel@pasglop>

On Fri, Jan 17, 2014 at 04:59:13PM +1100, Benjamin Herrenschmidt wrote:
> On Thu, 2014-01-16 at 20:52 -0800, Eric W. Biederman wrote:
> > 
> > I think we have largely survied until now because kdump is so popular
> > and kdump winds up having to reinitialize devices from any random
> > state.
> 
> kdump also doesn't care too much if the device is still DMA'ing to the
> old kernel memory :-)

In principle kdump does not care about ongoing DMAs but in practice it
is giving us some headaches with IOMMU. Various kind of issues crop up
during IOMMU intialization in second kernel while DMA is ongoing and
unfortunately no good solution has made into upstream yet.

Well, ongoing DMA and IOMMU seems to be orthogonal to using ->remove()
in kexec. So I will stop here. :-)

Thanks
Vivek

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

WARNING: multiple messages have this Message-ID (diff)
From: Vivek Goyal <vgoyal@redhat.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Matthew Garrett <matthew.garrett@nebula.com>,
	kexec@lists.infradead.org
Subject: Re: [Q] Why does kexec use device_shutdown rather than ubind them
Date: Fri, 17 Jan 2014 09:13:27 -0500	[thread overview]
Message-ID: <20140117141327.GC24394@redhat.com> (raw)
In-Reply-To: <1389938353.7406.22.camel@pasglop>

On Fri, Jan 17, 2014 at 04:59:13PM +1100, Benjamin Herrenschmidt wrote:
> On Thu, 2014-01-16 at 20:52 -0800, Eric W. Biederman wrote:
> > 
> > I think we have largely survied until now because kdump is so popular
> > and kdump winds up having to reinitialize devices from any random
> > state.
> 
> kdump also doesn't care too much if the device is still DMA'ing to the
> old kernel memory :-)

In principle kdump does not care about ongoing DMAs but in practice it
is giving us some headaches with IOMMU. Various kind of issues crop up
during IOMMU intialization in second kernel while DMA is ongoing and
unfortunately no good solution has made into upstream yet.

Well, ongoing DMA and IOMMU seems to be orthogonal to using ->remove()
in kexec. So I will stop here. :-)

Thanks
Vivek

  reply	other threads:[~2014-01-17 14:13 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-17  3:39 [Q] Why does kexec use device_shutdown rather than ubind them Benjamin Herrenschmidt
2014-01-17  3:39 ` Benjamin Herrenschmidt
2014-01-17  4:52 ` Eric W. Biederman
2014-01-17  4:52   ` Eric W. Biederman
2014-01-17  5:59   ` Benjamin Herrenschmidt
2014-01-17  5:59     ` Benjamin Herrenschmidt
2014-01-17 14:13     ` Vivek Goyal [this message]
2014-01-17 14:13       ` Vivek Goyal
2014-01-17 15:57       ` Sumner, William
2014-01-17 15:57         ` Sumner, William
2014-01-17 15:57         ` Sumner, William
2014-01-17 21:00       ` Benjamin Herrenschmidt
2014-01-17 21:00         ` Benjamin Herrenschmidt

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