Re: [Xen-devel] [RFC v4]Proposal to allow setting up shared memory areas between VMs from xl config file

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 31 Jul 2017, Wei Liu wrote:
> On Mon, Jul 31, 2017 at 01:09:04AM +0800, Zhongze Liu wrote:
> > 
> >   @cache_policy    Can only appear when @role = master.
> >                    The stage-2 cacheability/shareability attributes of the
> >                    shared memory area. Currently, only two policies are
> >                    supported:
> >                      * ARM_normal: Only applicable to ARM guests. This
> >                                    would mean Inner and Outer Write-Back
> >                                    Cacheable, and Inner Shareable.
> >                      * x86_normal: Only applicable to x86 HVM guests. This
> >                                    would mean Write-Back Cacheable.
> 
> This question might have been asked before, I'm sorry for not being
> able to follow closely previous discussions...
> 
> Why are these opaque names chosen instead of just writing "wb" "wc" or
> whatever?

Because "wb" and "wc" mean different things on ARM and x86. Also the
meaning of "wb" is not clear enough on ARM unless you also specify
shareability. It's simpler this way, and it gives us plenty of room to
improve the syntax in the future if we want to add more cacheability and
shareability modes while remaining backward compatible.

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