linux-kernel - Re: [PATCH v3 01/18] nitro_enclaves: Add ioctl interface definition

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Date:   Mon, 1 Jun 2020 10:20:18 +0300
From:   "Paraschiv, Andra-Irina" <andraprs@...zon.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Stefan Hajnoczi <stefanha@...il.com>
CC:     <linux-kernel@...r.kernel.org>,
        Anthony Liguori <aliguori@...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>,
        Alexander Graf <graf@...zon.de>,
        Martin Pohlack <mpohlack@...zon.de>,
        Matt Wilson <msw@...zon.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Balbir Singh <sblbir@...zon.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Stewart Smith <trawets@...zon.com>,
        Uwe Dannowski <uwed@...zon.de>, <kvm@...r.kernel.org>,
        <ne-devel-upstream@...zon.com>
Subject: Re: [PATCH v3 01/18] nitro_enclaves: Add ioctl interface definition



On 01/06/2020 06:02, Benjamin Herrenschmidt wrote:
> On Wed, 2020-05-27 at 09:49 +0100, Stefan Hajnoczi wrote:
>> What about feature bits or a API version number field? If you add
>> features to the NE driver, how will userspace detect them?
>>
>> Even if you intend to always compile userspace against the exact kernel
>> headers that the program will run on, it can still be useful to have an
>> API version for informational purposes and to easily prevent user
>> errors (running a new userspace binary on an old kernel where the API is
>> different).
>>
>> Finally, reserved struct fields may come in handy in the future. That
>> way userspace and the kernel don't need to explicitly handle multiple
>> struct sizes.
> Beware, Greg might disagree :)
>
> That said, yes, at least a way to query the API version would be
> useful.

I see there are several thoughts with regard to extensions possibilities. :)

I added an ioctl for getting the API version, we have now a way to query 
that info. Also, I updated the sample in this patch series to check for 
the API version.

Thanks,
Andra



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