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Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device
From: |
Jamie Lokier |
Subject: |
Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device |
Date: |
Tue, 9 Mar 2010 20:12:43 +0000 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
Paul Brook wrote:
> > On 03/08/2010 12:53 AM, Paul Brook wrote:
> > >> Support an inter-vm shared memory device that maps a shared-memory
> > >> object as a PCI device in the guest. This patch also supports
> > >> interrupts between guest by communicating over a unix domain socket.
> > >> This patch applies to the qemu-kvm repository.
> > >
> > > No. All new devices should be fully qdev based.
> > >
> > > I suspect you've also ignored a load of coherency issues, especially when
> > > not using KVM. As soon as you have shared memory in more than one host
> > > thread/process you have to worry about memory barriers.
> >
> > Shouldn't it be sufficient to require the guest to issue barriers (and
> > to ensure tcg honours the barriers, if someone wants this with tcg)?.
>
> In a cross environment that becomes extremely hairy. For example the x86
> architecture effectively has an implicit write barrier before every store,
> and
> an implicit read barrier before every load.
Btw, x86 doesn't have any implicit barriers due to ordinary loads.
Only stores and atomics have implicit barriers, afaik.
-- Jamie
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, (continued)
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Paul Brook, 2010/03/08
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Avi Kivity, 2010/03/08
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Jamie Lokier, 2010/03/09
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Anthony Liguori, 2010/03/09
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Avi Kivity, 2010/03/10
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Anthony Liguori, 2010/03/10
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Avi Kivity, 2010/03/10
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Paul Brook, 2010/03/10
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Avi Kivity, 2010/03/11
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Paul Brook, 2010/03/11
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device,
Jamie Lokier <=
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Paul Brook, 2010/03/09
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Cam Macdonell, 2010/03/09
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Avi Kivity, 2010/03/10
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Paul Brook, 2010/03/10
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Jamie Lokier, 2010/03/10
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, Nick Piggin, 2010/03/11
- Re: [Qemu-devel] [PATCH] Inter-VM shared memory PCI device, malc, 2010/03/11
[Qemu-devel] Re: [PATCH] Inter-VM shared memory PCI device, Avi Kivity, 2010/03/08