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

[Sean Christopherson]

On Mon, Sep 03, 2018 at 05:41:53PM +0300, Andy Shevchenko wrote:
> On Mon, Aug 27, 2018 at 9:58 PM Jarkko Sakkinen
> <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote:
> 
> > +       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.

For documentation purposes, maybe it would be better to use __private
or "#define __sgx_epc __iomem" and use that?