linux-kernel - Re: [PATCH 1/2] x86/mce: Only restart instruction after machine check recovery if it is safe

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Message-ID: <20120514171702.GC21960@aftab.osrc.amd.com>
Date:	Mon, 14 May 2012 19:17:02 +0200
From:	Borislav Petkov <bp@...64.org>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	Borislav Petkov <bp@...64.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Chen Gong <gong.chen@...ux.intel.com>,
	"Huang, Ying" <ying.huang@...el.com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Subject: Re: [PATCH 1/2] x86/mce: Only restart instruction after machine
 check recovery if it is safe

On Mon, May 14, 2012 at 04:16:05PM +0000, Luck, Tony wrote:
> >> +	int			restartable;
> >
> > Is it me or does this look like a flag, or a bitfield? Instead of
> > wasting a whole integer for a single bit of information.
> 
> I could make it "int flags;" and "#define MCE_INFO_RESTARTABLE 1"
> to make it clear that we have lots more bits available for special
> cases?

I was wondering about that but don't have any other flags/use cases.
Well, we can always change it later if needed.

> > It will probably end up the same size though due to compiler padding
> > since this struct is currently 4 + 2*8 byte without the ->restartable
> > thing.
> 
> Yup - we can't save any memory (unless we introduce more complexity to
> the code ... low PAGE_SHIFT bits of the "paddr" field are simply thrown
> away ... so we could allocate a bit there ... but I don't think that
> the resulting ugliness is worth the memory savings).

Agreed, that would be too ugly for no reason :-)

-- 
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Boris.

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