Re: [Xen-devel] [PATCH] include/public/io/ring.h: Remove xen_mb, xen_rmb, xen_wmb macros

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich <JBeulich@xxxxxxxx>
> Sent: 04 July 2019 16:49
> To: Anthony Perard <anthony.perard@xxxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Paul Durrant <Paul.Durrant@xxxxxxxxxx>; 
> Konrad Rzeszutek Wilk
> <konrad.wilk@xxxxxxxxxx>; Juergen Gross <JGross@xxxxxxxx>
> Subject: Re: [Xen-devel] [PATCH] include/public/io/ring.h: Remove xen_mb, 
> xen_rmb, xen_wmb macros
> 
> On 04.07.2019 17:15, Anthony PERARD wrote:
> > Those macros where introduced when a prefix "xen_" was added to
> > mb,rmb,wmb. There are gated on __XEN_INTERFACE_VERSION__, but there
> > are not part of the Xen interface. Users of ring.h needs to provide
> > xen_[rw]?mb() anywai because [rw]?mb() isn't likely to exist.
> 
> It's not clear to me what you want to achieve:
> 

The issue is that any project importing this header (in this case QEMU, but I 
have the same issue in the Windows PV drivers) needs to import xen-compat.h (or 
dream up a header of the same name), even though this header is only concerned 
with the underpinnings of PV protocols and has nothing, as such, to do with Xen.

To keep old verbatim users (are there really any at all?) happy, how about 
simple...

#ifndef xen_mb()
#define xen_mb() mb()
#endif

constructs?

  Paul
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