linux-kernel - Re: [PATCH RESEND 0/3] x86/sgx: eextend ioctl

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Message-ID: <7c93136a-3906-e225-3007-ebf13569ab52@fortanix.com>
Date:   Thu, 8 Apr 2021 17:07:17 +0200
From:   Jethro Beekman <jethro@...tanix.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Raoul Strackx <raoul.strackx@...tanix.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 0/3] x86/sgx: eextend ioctl

On 2021-04-04 18:04, Jarkko Sakkinen wrote:
> 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".

How is that the same? Please make an effort to reasonably interpret what I'm saying.

--
Jethro Beekman | Fortanix




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