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

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Date:   Tue, 4 Sep 2018 12:59:23 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        sean.j.christopherson@...el.com, nhorman@...hat.com,
        npmccallum@...hat.com, linux-sgx@...r.kernel.org,
        serge.ayoun@...el.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, suresh.b.siddha@...el.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v13 07/13] x86/sgx: Add data structures for tracking the
 EPC pages

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@...ux.intel.com> wrote:
> >
> > Add data structures to track Enclave Page Cache (EPC) pages.  EPC is
> > divided into multiple banks (1-N) of which addresses and sizes can be
> > enumerated with CPUID by the OS.
> >
> > On NUMA systems a node can have at most bank. A bank can be at most part of
> > two nodes. SGX supports both nodes with a single memory controller and also
> > sub-cluster nodes with severals memory controllers on a single die.
> 
> > -#include <asm/sgx.h>
> > -#include <asm/sgx_pr.h>
> >  #include <linux/freezer.h>
> >  #include <linux/highmem.h>
> >  #include <linux/kthread.h>
> > +#include <linux/pagemap.h>
> >  #include <linux/ratelimit.h>
> >  #include <linux/sched/signal.h>
> > +#include <linux/shmem_fs.h>
> >  #include <linux/slab.h>
> > +#include <asm/sgx.h>
> > +#include <asm/sgx_pr.h>
> 
> Squash issues?

Yes :-/

> > +       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.

Had this idea a long time ago but had forgotten it. EPC is from caching
perspective like regular memory.

> -- 
> With Best Regards,
> Andy Shevchenko
> 

/Jarkko