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Date: Fri, 9 Nov 2018 00:31:26 +0300
From: Cyrill Gorcunov <gorcunov@gmail.com>
Subject: Re: [PATCH v5 04/27] x86/fpu/xstate: Add XSAVES system states for
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To: Andy Lutomirski <luto@amacapital.net>
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On Thu, Nov 08, 2018 at 01:22:54PM -0800, Andy Lutomirski wrote:
> > >
> > > Why are these __packed?  It seems like it'll generate bad code for no
> > > obvious purpose.
> >
> > That prevents any possibility that the compiler will insert padding, although in
> > 64-bit kernel this should not happen to either struct.  Also all xstate
> > components here are packed.
> >
> 
> They both seem like bugs, perhaps.  As I understand it, __packed
> removes padding, but it also forces the compiler to expect the fields
> to be unaligned even if they are actually aligned.

How is that? Andy, mind to point where you get that this
attribute forces compiler to make such assumption?