linux-kernel - Re: [PATCH 3/6] intel_sgx: driver for Intel Secure Guard eXtensions

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Date:	Mon, 9 May 2016 10:06:00 +0300
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Jethro Beekman <kernel@...ekman.nl>
Cc:	gregkh@...uxfoundation.org,
	"open list:STAGING SUBSYSTEM" <devel@...verdev.osuosl.org>,
	"maintainer:X86 ARCHITECTURE 32-BIT AND 64-BIT" <x86@...nel.org>,
	"open list:X86 ARCHITECTURE 32-BIT AND 64-BIT" 
	<linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3/6] intel_sgx: driver for Intel Secure Guard eXtensions

On Mon, May 09, 2016 at 08:29:17AM +0300, Jarkko Sakkinen wrote:
> On Fri, Apr 29, 2016 at 03:22:19PM -0700, Jethro Beekman wrote:
> > On 29-04-16 13:04, Jarkko Sakkinen wrote:
> > >>> Why would you want to do that?
> > >>
> > >> ...
> > >
> > > Do you see this as a performance issue or why do you think that this
> > > would hurt that much?
> > 
> > I don't think it's a performance issue at all. I'm just giving an example of why
> > you'd want to do this. I'm sure people who want to use this instruction set can
> > come up with other uses, so I think the driver should support it. Other drivers
> > on different platform might support this, in which case we should be compatible
> > (to achieve the same enclave measurement). Other Linux drivers support it [1]. I
> > would ask: why would you not want to do this? It seems trivial to expand the
> > current flag into 16 separate flags; one for each 256-byte chunk in the page.
> 
> I'm fine with adding a 16-bit bitmask.

I did some experiementation and since this doesn't make the API more
complicated it is probably ok.

Field that I declared was:

  __u16 mrmask;

Measure one page:

  add_page.mrmask = ~0;

Skip the measurement:

  add_page.mrmask = 0:

/Jarkko