Re: [Xen-devel] [PATCH] xen/arm: flush icache as well when XEN_DOMCTL_cacheflush is issued

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Jan 27, 2017 at 09:32:25AM -0700, Tamas K Lengyel wrote:
> On Fri, Jan 27, 2017 at 9:29 AM, Julien Grall <julien.grall@xxxxxxx> wrote:
> > Hi Tamas,
> >
> > On 27/01/17 16:23, Tamas K Lengyel wrote:
> >>
> >> On Fri, Jan 27, 2017 at 9:15 AM, Julien Grall <julien.grall@xxxxxxx>
> >> wrote:
> >>>
> >>> Hello,
> >>>
> >>> On 27/01/17 15:52, Tamas K Lengyel wrote:
> >>>>
> >>>>
> >>>> Well, yes, only ARM could _should_ call this function. The comment I
> >>>> think is important to tell the user don't expect it to do anything on
> >>>> x86.  Doesn't mean they can't call it though - if that was the case it
> >>>> would be wrapped in an ifdef like all the other architecture specific
> >>>> bits in the header. I would think that's pretty straight forward. No
> >>>> objection to clarifing the comment though if it helps.
> >>>
> >>>
> >>>
> >>> If you looked at the commit log, the #ifdef was added to avoid calling
> >>> the
> >>> hypervisor for nothing and therefore saving few hundred cycles bit of
> >>> time.
> >>> Technically speaking, this helper abstracts the architectural behavior of
> >>> the cache. So it makes sense to call it on x86 even if it is a nop.
> >>
> >>
> >> Except that on x86 the user should be aware that it returns an error,
> >> which is normal and can be ignored.
> >
> >
> > It looks like the current callers does not check the return. However, it
> > would more make sense to return 0 if we expect nothing to be done rather
> > than -ENOSYS.
> >
> 
> That would be fine by me. Wei, what do you think?
> 

No objection from me.

> Tamas

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