From: Joerg Roedel <joro@8bytes.org>
To: Avi Kivity <avi@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
Alexey Kardashevskiy <aik@au1.ibm.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Paul Mackerras <pmac@au1.ibm.com>,
"Roedel, Joerg" <Joerg.Roedel@amd.com>,
qemu-devel <qemu-devel@nongnu.org>,
Alexander Graf <agraf@suse.de>, chrisw <chrisw@sous-sol.org>,
iommu <iommu@lists.linux-foundation.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
"benve@cisco.com" <benve@cisco.com>
Subject: Re: [Qemu-devel] kvm PCI assignment & VFIO ramblings
Date: Sun, 28 Aug 2011 15:56:33 +0200 [thread overview]
Message-ID: <20110828135632.GG8978@8bytes.org> (raw)
In-Reply-To: <4E5A3F18.7050903@redhat.com>
On Sun, Aug 28, 2011 at 04:14:00PM +0300, Avi Kivity wrote:
> On 08/26/2011 12:24 PM, Roedel, Joerg wrote:
>> The biggest problem with this approach is that it has to happen in the
>> context of the given process. Linux can't really modify an mm which
>> which belong to another context in a safe way.
>>
>
> Is use_mm() insufficient?
Yes, it introduces a set of race conditions when a process that already
has an mm wants to take over another processes mm temporarily (and when
use_mm is modified to actually provide this functionality). It is only
save when used from kernel-thread context.
One example:
Process A Process B Process C
. . .
. <-- takes A->mm .
. and assignes as B->mm .
. . --> Wants to take
. . B->mm, but gets
A->mm now
This can't be secured by a lock, because it introduces potential
A->B<-->B->A lock problem when two processes try to take each others mm.
It could probably be solved by a task->real_mm pointer, havn't thought
about this yet...
Joerg
next prev parent reply other threads:[~2011-08-28 13:56 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1311983933.8793.42.camel@pasglop>
2011-07-30 18:20 ` [Qemu-devel] kvm PCI assignment & VFIO ramblings Alex Williamson
2011-07-30 23:54 ` Benjamin Herrenschmidt
2011-08-01 18:59 ` Alex Williamson
2011-08-02 2:00 ` Benjamin Herrenschmidt
2011-07-30 23:55 ` Benjamin Herrenschmidt
2011-08-02 8:28 ` David Gibson
2011-08-02 18:14 ` Alex Williamson
2011-08-02 18:35 ` Alex Williamson
2011-08-03 2:04 ` David Gibson
2011-08-03 3:44 ` Alex Williamson
2011-08-04 0:39 ` David Gibson
2011-08-08 8:28 ` Avi Kivity
2011-08-09 23:24 ` Alex Williamson
2011-08-10 2:48 ` Benjamin Herrenschmidt
2011-08-20 16:51 ` Alex Williamson
2011-08-22 5:55 ` David Gibson
2011-08-22 15:45 ` Alex Williamson
2011-08-22 21:01 ` Benjamin Herrenschmidt
2011-08-23 19:30 ` Alex Williamson
2011-08-23 23:51 ` Benjamin Herrenschmidt
2011-08-24 3:40 ` Alexander Graf
2011-08-24 14:47 ` Alex Williamson
2011-08-24 8:43 ` Joerg Roedel
2011-08-24 14:56 ` Alex Williamson
2011-08-25 11:01 ` Roedel, Joerg
2011-08-23 2:38 ` David Gibson
2011-08-23 16:23 ` Alex Williamson
2011-08-23 23:41 ` Benjamin Herrenschmidt
2011-08-24 3:36 ` Alexander Graf
2011-08-22 6:30 ` Avi Kivity
2011-08-22 10:46 ` Joerg Roedel
2011-08-22 10:51 ` Avi Kivity
2011-08-22 12:36 ` Roedel, Joerg
2011-08-22 12:42 ` Avi Kivity
2011-08-22 12:55 ` Roedel, Joerg
2011-08-22 13:06 ` Avi Kivity
2011-08-22 13:15 ` Roedel, Joerg
2011-08-22 13:17 ` Avi Kivity
2011-08-22 14:37 ` Roedel, Joerg
2011-08-22 20:53 ` Benjamin Herrenschmidt
2011-08-22 17:25 ` Joerg Roedel
2011-08-22 19:17 ` Alex Williamson
2011-08-23 13:14 ` Roedel, Joerg
2011-08-23 17:08 ` Alex Williamson
2011-08-24 8:52 ` Roedel, Joerg
2011-08-24 15:07 ` Alex Williamson
2011-08-25 12:31 ` Roedel, Joerg
2011-08-25 13:25 ` Alexander Graf
2011-08-26 4:24 ` David Gibson
2011-08-26 9:24 ` Roedel, Joerg
2011-08-28 13:14 ` Avi Kivity
2011-08-28 13:56 ` Joerg Roedel [this message]
2011-08-28 14:04 ` Avi Kivity
2011-08-30 16:14 ` Joerg Roedel
2011-08-22 21:03 ` Benjamin Herrenschmidt
2011-08-23 13:18 ` Roedel, Joerg
2011-08-23 23:35 ` Benjamin Herrenschmidt
2011-08-24 8:53 ` Roedel, Joerg
2011-08-22 20:29 ` aafabbri
2011-08-22 20:49 ` Benjamin Herrenschmidt
2011-08-22 21:38 ` aafabbri
2011-08-22 21:49 ` Benjamin Herrenschmidt
2011-08-23 0:52 ` aafabbri
2011-08-23 6:54 ` Benjamin Herrenschmidt
2011-08-23 11:09 ` Joerg Roedel
2011-08-23 17:01 ` Alex Williamson
2011-08-23 17:33 ` Aaron Fabbri
2011-08-23 18:01 ` Alex Williamson
2011-08-24 9:10 ` Joerg Roedel
2011-08-24 21:13 ` Alex Williamson
2011-08-25 10:54 ` Roedel, Joerg
2011-08-25 15:38 ` Don Dutile
2011-08-25 16:46 ` Roedel, Joerg
2011-08-25 17:20 ` Alex Williamson
2011-08-25 18:05 ` Joerg Roedel
2011-08-26 18:04 ` Alex Williamson
2011-08-30 16:13 ` Joerg Roedel
2011-08-23 11:04 ` Joerg Roedel
2011-08-23 16:54 ` aafabbri
2011-08-24 9:14 ` Roedel, Joerg
2011-08-24 9:33 ` David Gibson
2011-08-24 11:03 ` Roedel, Joerg
2011-08-26 4:20 ` David Gibson
2011-08-26 9:33 ` Roedel, Joerg
2011-08-26 14:07 ` Alexander Graf
2011-08-26 15:24 ` Joerg Roedel
2011-08-26 15:29 ` Alexander Graf
2011-08-26 17:52 ` Aaron Fabbri
2011-08-26 19:35 ` Chris Wright
2011-08-26 20:17 ` Aaron Fabbri
2011-08-26 21:06 ` Chris Wright
2011-08-30 1:29 ` David Gibson
2011-08-04 10:35 ` Joerg Roedel
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