Re: [PATCH v13 07/13] x86/sgx: Add data structures for tracking the EPC pages

[Sean Christopherson]

On Tue, Sep 04, 2018 at 09:01:15PM +0300, Andy Shevchenko wrote:
> On Tue, Sep 4, 2018 a> +/**
> 
> > > > +       va = ioremap_cache(addr, size);
> > > > +       if (!va)
> > > > +               return -ENOMEM;
> > >
> > > I'm not sure this is a right API. Do we operate with memory? Does it
> > > have I/O side effects?
> > > If no, memremap() would be better to use.
> >
> > Preserving __iomem is desirable.  There aren't side effects per se,
> > but direct non-enclave accesses to the EPC get abort page semantics so
> > the kernel shouldn't be directly dereferencing a pointer to the EPC.
> > Though by that argument, sgx_epc_bank.va, sgx_epc_addr's return and
> > all ENCLS helpers should be tagged __iomem.
> 
> Why?
> Does it related to *any* I/O?

No, hence my other comment that __private or a new tag altogether may
be more appropriate.  The noderef attribute is what we truly care
about.