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

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Date:	Fri, 29 Apr 2016 23:04:49 +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 Wed, Apr 27, 2016 at 04:32:23PM -0700, Jethro Beekman wrote:
> On 27-04-16 05:40, Jarkko Sakkinen wrote:
> >> The hardware supports calling EEXTEND on only a part of a page, I think the
> >> driver should also support that.
> >
> > Why would you want to do that?
> 
> You might have segments in a binary that don't start at the beginning of a page
> or that end before the end of a page. For example:
> 
>   Type           Offset             VirtAddr           PhysAddr
>                  FileSiz            MemSiz              Flags  Align
>   LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
>                  0x000000000001bcac 0x000000000001bcac  R E    1000
>   LOAD           0x000000000001c8e8 0x000000000001c8e8 0x000000000001c8e8
>                  0x0000000000000790 0x0000000000000c68  RW     1000
> 
> There's no need to measure the extra padding (0x1bd00--0x1c7ff and
> 0x1cb00--0x1cfff) in this case.

Do you see this as a performance issue or why do you think that this
would hurt that much?

> Jethro

/Jarkko