Re: [Xen-devel] [PATCH 1/4] xen/arm: introduce invalidate_xen_dcache_va_range

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-10-02 at 12:57 +0100, Julien Grall wrote:
> Hi Stefano,
> 
> n 10/02/2014 11:02 AM, Stefano Stabellini wrote:
> > +
> > +static inline void invalidate_xen_dcache_va_range(const void *p, unsigned 
> > long size)
> > +{
> > +    size_t off;
> > +    const void *end = p + size;
> > +
> > +    dsb(sy);           /* So the CPU issues all writes to the range */
> 
> I'm wondering if we could relax the dsb(sy) to dsb(ish)?

We would need to know which cache level the device we are talking to is
coherent with, which we don't know so we have to be conservative.

Also since you only need this hypercall for incoherent devices I suppose
it needs to push things all the way down.

Ian.


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