From: Paul Brook <paul@codesourcery.com>
To: Avi Kivity <avi@redhat.com>
Cc: Cam Macdonell <cam@cs.ualberta.ca>,
Jamie Lokier <jamie@shareable.org>,
qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device
Date: Wed, 10 Mar 2010 11:13:10 +0000 [thread overview]
Message-ID: <201003101113.11974.paul@codesourcery.com> (raw)
In-Reply-To: <4B97668C.3060203@redhat.com>
> >> As of March 2009[1] Intel guarantees that memory reads occur in order
> >> (they may only be reordered relative to writes). It appears AMD do not
> >> provide this guarantee, which could be an interesting problem for
> >> heterogeneous migration..
> >
> > Interesting, but what ordering would cause problems that AMD would do
> > but Intel wouldn't? Wouldn't that ordering cause the same problems
> > for POSIX shared memory in general (regardless of Qemu) on AMD?
>
> If some code was written for the Intel guarantees it would break if
> migrated to AMD. Of course, it would also break if run on AMD in the
> first place.
Right. This is independent of shared memory, and is a case where reporting an
Intel CPUID on and AMD host might get you into trouble.
Paul
WARNING: multiple messages have this Message-ID (diff)
From: Paul Brook <paul@codesourcery.com>
To: Avi Kivity <avi@redhat.com>
Cc: Cam Macdonell <cam@cs.ualberta.ca>,
qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device
Date: Wed, 10 Mar 2010 11:13:10 +0000 [thread overview]
Message-ID: <201003101113.11974.paul@codesourcery.com> (raw)
In-Reply-To: <4B97668C.3060203@redhat.com>
> >> As of March 2009[1] Intel guarantees that memory reads occur in order
> >> (they may only be reordered relative to writes). It appears AMD do not
> >> provide this guarantee, which could be an interesting problem for
> >> heterogeneous migration..
> >
> > Interesting, but what ordering would cause problems that AMD would do
> > but Intel wouldn't? Wouldn't that ordering cause the same problems
> > for POSIX shared memory in general (regardless of Qemu) on AMD?
>
> If some code was written for the Intel guarantees it would break if
> migrated to AMD. Of course, it would also break if run on AMD in the
> first place.
Right. This is independent of shared memory, and is a case where reporting an
Intel CPUID on and AMD host might get you into trouble.
Paul
next prev parent reply other threads:[~2010-03-10 11:13 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-05 23:52 [PATCH] Support adding a file to qemu's ram allocation Cam Macdonell
2010-03-05 23:52 ` [Qemu-devel] " Cam Macdonell
2010-03-05 23:52 ` [PATCH] Inter-VM shared memory PCI device Cam Macdonell
2010-03-05 23:52 ` [Qemu-devel] " Cam Macdonell
2010-03-07 22:53 ` Paul Brook
2010-03-08 1:45 ` Jamie Lokier
2010-03-08 1:45 ` Jamie Lokier
2010-03-08 9:48 ` Alexander Graf
2010-03-08 9:48 ` Alexander Graf
2010-03-08 9:54 ` Jamie Lokier
2010-03-08 9:54 ` Jamie Lokier
2010-03-08 10:57 ` Alexander Graf
2010-03-08 10:57 ` Alexander Graf
2010-03-09 21:41 ` Anthony Liguori
2010-03-09 21:41 ` Anthony Liguori
2010-03-08 13:04 ` Paul Brook
2010-03-08 13:04 ` Paul Brook
2010-03-09 19:00 ` Jamie Lokier
2010-03-09 19:00 ` Jamie Lokier
2010-03-08 9:52 ` Avi Kivity
2010-03-08 9:52 ` Avi Kivity
2010-03-08 13:03 ` Paul Brook
2010-03-08 13:03 ` Paul Brook
2010-03-08 13:16 ` Avi Kivity
2010-03-08 13:16 ` Avi Kivity
2010-03-09 20:11 ` Jamie Lokier
2010-03-09 20:11 ` Jamie Lokier
2010-03-09 21:44 ` Anthony Liguori
2010-03-09 21:44 ` [Qemu-devel] " Anthony Liguori
2010-03-10 9:25 ` Avi Kivity
2010-03-10 9:25 ` [Qemu-devel] " Avi Kivity
2010-03-10 17:13 ` Anthony Liguori
2010-03-10 17:13 ` Anthony Liguori
2010-03-10 17:30 ` Avi Kivity
2010-03-10 17:30 ` Avi Kivity
2010-03-10 17:41 ` Paul Brook
2010-03-10 17:41 ` Paul Brook
2010-03-11 6:33 ` Avi Kivity
2010-03-11 6:33 ` Avi Kivity
2010-03-11 12:21 ` Paul Brook
2010-03-11 12:21 ` Paul Brook
2010-03-09 20:12 ` Jamie Lokier
2010-03-09 20:12 ` Jamie Lokier
2010-03-10 0:03 ` Paul Brook
2010-03-10 0:03 ` Paul Brook
2010-03-10 4:38 ` Cam Macdonell
2010-03-10 4:38 ` [Qemu-devel] " Cam Macdonell
2010-03-10 9:29 ` Avi Kivity
2010-03-10 9:29 ` [Qemu-devel] " Avi Kivity
2010-03-10 11:13 ` Paul Brook [this message]
2010-03-10 11:13 ` Paul Brook
2010-03-11 3:10 ` Jamie Lokier
2010-03-11 3:10 ` Jamie Lokier
2010-03-11 4:37 ` Nick Piggin
2010-03-11 4:37 ` Nick Piggin
2010-03-11 14:38 ` malc
2010-03-11 14:38 ` [Qemu-devel] " malc
2010-03-08 9:56 ` Avi Kivity
2010-03-08 9:56 ` [Qemu-devel] " Avi Kivity
2010-03-08 17:57 ` Cam Macdonell
2010-03-08 17:57 ` [Qemu-devel] " Cam Macdonell
2010-03-09 10:29 ` Avi Kivity
2010-03-09 10:29 ` [Qemu-devel] " Avi Kivity
[not found] ` <8286e4ee1003090724m1ef0b571g8b705a24e36e1753@mail.gmail.com>
2010-03-09 15:27 ` Cam Macdonell
2010-03-09 15:27 ` [Qemu-devel] " Cam Macdonell
2010-03-09 17:28 ` Avi Kivity
2010-03-09 17:28 ` [Qemu-devel] " Avi Kivity
2010-03-09 17:34 ` Anthony Liguori
2010-03-09 17:34 ` [Qemu-devel] " Anthony Liguori
2010-03-09 18:34 ` Cam Macdonell
2010-03-09 18:34 ` [Qemu-devel] " Cam Macdonell
2010-03-10 9:21 ` Avi Kivity
2010-03-10 9:21 ` [Qemu-devel] " Avi Kivity
2010-03-10 16:36 ` Cam Macdonell
2010-03-10 16:36 ` [Qemu-devel] " Cam Macdonell
2010-03-11 6:49 ` Avi Kivity
2010-03-11 6:49 ` [Qemu-devel] " Avi Kivity
2010-03-09 12:49 ` Arnd Bergmann
2010-03-09 12:49 ` [Qemu-devel] " Arnd Bergmann
2010-03-09 13:03 ` Avi Kivity
2010-03-09 13:03 ` [Qemu-devel] " Avi Kivity
2010-03-09 16:44 ` Cam Macdonell
2010-03-09 16:44 ` [Qemu-devel] " Cam Macdonell
2010-03-10 14:04 ` Arnd Bergmann
2010-03-10 14:04 ` [Qemu-devel] " Arnd Bergmann
2010-03-11 6:50 ` Avi Kivity
2010-03-11 6:50 ` [Qemu-devel] " Avi Kivity
2010-03-11 12:57 ` Arnd Bergmann
2010-03-11 12:57 ` [Qemu-devel] " Arnd Bergmann
2010-03-11 13:07 ` Avi Kivity
2010-03-11 13:07 ` [Qemu-devel] " Avi Kivity
2010-03-11 14:32 ` Arnd Bergmann
2010-03-11 14:32 ` [Qemu-devel] " Arnd Bergmann
2010-03-08 9:53 ` [PATCH] Support adding a file to qemu's ram allocation Avi Kivity
2010-03-08 9:53 ` [Qemu-devel] " Avi Kivity
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