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Date:   Wed, 27 May 2020 00:21:09 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     "Paraschiv, Andra-Irina" <andraprs@amazon.com>
Cc:     linux-kernel@vger.kernel.org,
        Anthony Liguori <aliguori@amazon.com>,
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        Uwe Dannowski <uwed@amazon.de>, kvm@vger.kernel.org,
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Subject: Re: [PATCH v3 02/18] nitro_enclaves: Define the PCI device interface
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On Tue, May 26, 2020 at 08:01:36PM +0300, Paraschiv, Andra-Irina wrote:
> 
> 
> On 26/05/2020 09:44, Greg KH wrote:
> > On Tue, May 26, 2020 at 01:13:18AM +0300, Andra Paraschiv wrote:
> > > +struct enclave_get_slot_req {
> > > +	/* Context ID (CID) for the enclave vsock device. */
> > > +	u64 enclave_cid;
> > > +} __attribute__ ((__packed__));
> > Can you really "pack" a single member structure?
> > 
> > Anyway, we have better ways to specify this instead of the "raw"
> > __attribute__ option.  But first see if you really need any of these, at
> > first glance, I do not think you do at all, and they can all be removed.
> 
> There are a couple of data structures with more than one member and multiple
> field sizes. And for the ones that are not, gathered as feedback from
> previous rounds of review that should consider adding a "flags" field in
> there for further extensibility.

Please do not do that in ioctls.  Just create new calls instead of
trying to "extend" existing ones.  It's always much easier.

> I can modify to have "__packed" instead of the attribute callout.

Make sure you even need that, as I don't think you do for structures
like the above one, right?

thanks,

greg k-h