linux-kernel - Re: [PATCH v1 00/15] Add support for Nitro Enclaves

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Date:   Wed, 29 Apr 2020 15:20:01 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Alexander Graf <graf@...zon.com>,
        "Paraschiv, Andra-Irina" <andraprs@...zon.com>,
        linux-kernel@...r.kernel.org
Cc:     Anthony Liguori <aliguori@...zon.com>,
        Benjamin Herrenschmidt <benh@...zon.com>,
        Colm MacCarthaigh <colmmacc@...zon.com>,
        Bjoern Doebel <doebel@...zon.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Frank van der Linden <fllinden@...zon.com>,
        Martin Pohlack <mpohlack@...zon.de>,
        Matt Wilson <msw@...zon.com>, Balbir Singh <sblbir@...zon.com>,
        Stewart Smith <trawets@...zon.com>,
        Uwe Dannowski <uwed@...zon.de>, kvm@...r.kernel.org,
        ne-devel-upstream@...zon.com
Subject: Re: [PATCH v1 00/15] Add support for Nitro Enclaves

On 28/04/20 17:07, Alexander Graf wrote:
>> So why not just start running the enclave at 0xfffffff0 in real mode?
>> Yes everybody hates it, but that's what OSes are written against.  In
>> the simplest example, the parent enclave can load bzImage and initrd at
>> 0x10000 and place firmware tables (MPTable and DMI) somewhere at
>> 0xf0000; the firmware would just be a few movs to segment registers
>> followed by a long jmp.
> 
> There is a bit of initial attestation flow in the enclave, so that
> you can be sure that the code that is running is actually what you wanted to
> run.

Can you explain this, since it's not documented?

>   vm = ne_create(vcpus = 4)
>   ne_set_memory(vm, hva, len)
>   ne_load_image(vm, addr, len)
>   ne_start(vm)
> 
> That way we would get the EIF loading into kernel space. "LOAD_IMAGE"
> would only be available in the time window between set_memory and start.
> It basically implements a memcpy(), but it would completely hide the
> hidden semantics of where an EIF has to go, so future device versions
> (or even other enclave implementers) could change the logic.
> 
> I think it also makes sense to just allocate those 4 ioctls from
> scratch. Paolo, would you still want to "donate" KVM ioctl space in that
> case?

Sure, that's not a problem.

Paolo

> Overall, the above should address most of the concerns you raised in
> this mail, right? It still requires copying, but at least we don't have
> to keep the copy in kernel space.