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Re: [patch] x86_*fence replaced by membar_ops(3)
On Thu, Jan 15, 2009 at 03:13:59PM +0100, Jean-Yves Migeon wrote:
> >>What should I do? Drop it for the x86 generic bus code, and keep it for
> >>the Xen drivers?
> >No, membar_ops won't work for bus_dma/bus_space either. membar_ops are
> >to be NOP on UP kernels, still they're needed for interfaces with
> Hmm, I was not really clear on that one: I just meant to keep the
> membar_ops(3) routines for the xennet, xbd and xencons drivers: since we
> do not patch the LOCK prefix for UP Xen domains, they are close to the
> x86_*fence() ones.
Actually yes; but we'll probably want to use x86_patch() in the future.
> I will just handle it the other way around. I'll keep the x86 MD fences
> and replace the ones inside Xen with their xen_[rw]mb() equivalents.
> Any consideration on this one though:
> Is it really needed to have load-before-load ordering here? If we issue
> the hypercall, that will be a barrier anyway, and the RING macros from
> Xen do implement barrier for notify, so...
you're right, this barrier is not needed.
Manuel Bouyer, LIP6, Universite Paris VI.
NetBSD: 26 ans d'experience feront toujours la difference
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