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Date:   Sun, 4 Apr 2021 19:04:18 +0300
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Jethro Beekman <jethro@fortanix.com>
Cc:     Dave Hansen <dave.hansen@intel.com>,
        Raoul Strackx <raoul.strackx@fortanix.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RESEND 0/3] x86/sgx: eextend ioctl
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On Fri, Apr 02, 2021 at 08:31:19PM +0200, Jethro Beekman wrote:
> On 2021-04-02 17:53, Dave Hansen wrote:
> > On 4/2/21 1:38 AM, Jethro Beekman wrote:
> >>> So, we're talking here about pages that have been EEADDED, but for
> >>> which we do not want to include the entire contents of the page?
> >>> Do these contents always include the beginning of the page, or can
> >>> the holes be anywhere?
> >> Holes can be anywhere, and EEXTEND calls need not be sequential in
> >> memory address or even relate to the most recently EADDed page.
> > 
> > I think you're referring to the SGX architecture itself here.  The
> > architecture permits this, right?
> 
> Yes.
> 
> > But, why would an enclave loader application ever do this? 
> 
> e.g. to save space
> 
> > Is this something we want to support in Linux?
> 
> Why not? Is there a good reason to not fully support this part of the CPU architecture?

Yes, in generic sense :-)

If one would disagree, that would be same as saying that everything should
execute in ring-0 because that only gives "full support".

/Jarkko