linux-kernel - Re: [PATCH 4/7] x86, mce: create helper function to save addr/misc when needed

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Date:	Wed, 14 Dec 2011 17:09:29 +0100
From:	Borislav Petkov <bp@...64.org>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	Ingo Molnar <mingo@...e.hu>, "Huang, Ying" <ying.huang@...el.com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/7] x86, mce: create helper function to save addr/misc
 when needed

On Tue, Dec 13, 2011 at 09:44:07AM -0800, Luck, Tony wrote:
> > Am I reading this correctly in that you need to cut off the same amount
> > of bits on both sides of MCi_ADDR and the address magnitude coincides
> > with the left shift amount? I.e. and for example, if MCi_ADDR[44:3]
> > and you need to cut off 3 bits of both sides to get a 48-bit physical
> > address?
> 
> No - just masking bits at the low end (shift right and the bits we don't
> want fall into the bit bucket, shift left by the same amount and we fill
> those spots with zeroes).  Upper bits are unchanged.

Doh, of course, I must be drunk. Please disregard this comment.

> 
> I could write it as:
> 			m->addr &= ~((1ull << shift) - 1);

> 
> But I think the shift-right, shift-left is used elsewhere in the kernel too.

No, yours is fine.

ACK.

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