Re: [Xen-devel] [PATCH v4 4/7] xen, common: add the XEN_DOMCTL_memory_mapping hypercall

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 25 Mar 2014, Jan Beulich wrote:
> >>> On 25.03.14 at 13:35, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > On Tue, 25 Mar 2014, Arianna Avanzini wrote:
> >> +            add = unmap_mmio_regions(d, gfn, gfn_end - 1, mfn);
> >> +            ret = iomem_deny_access(d, mfn, mfn_end - 1);
> >> +            if ( ret && add )
> >> +                ret = -EIO;
> > 
> > This is a functional change. The removed code did:
> > 
> > -            ret = iomem_deny_access(d, mfn, mfn + nr_mfns - 1);
> > -            if ( !ret && add )
> > -                ret = -EIO;
> > 
> > The change looks correct to me, but I would appreciate if you could
> > mention it explicitly in the commit message.
> 
> I overlooked this, and no, it is not correct (and I don't follow why
> you think it is): We only want to force ret to -EIO if
> iomem_deny_access() didn't already return another error.

I thought that the intention was to return -EIO if unmap_mmio_regions
failed, even if iomem_deny_access is successful.
iomem_deny_access errors should be taken care by the
iomem_access_permitted check above, returning -EPERM.

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