linux-kernel - Re: [PATCH] x86: make DR6_RESERVED/DR_CONTROL

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Date:	Wed, 20 Nov 2013 13:48:00 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: make DR6_RESERVED/DR_CONTROL_RESERVED unsigned long

On Tue, Nov 19, 2013 at 08:21:45PM +0100, Oleg Nesterov wrote:
> DR6_RESERVED and DR_CONTROL_RESERVED are used to clear the unwanted
> bits in the "unsigned long" data, but "ulong &= ~int" also clears the
> upper bits that are not specified in mask.
> 
> This is actually fine, dr6[32:63] are reserved, but this is not clear
> so it would be better to make them "unsigned long" to cleanup the code.
> 
> However, depending on sizeof(long), DR6_RESERVED should be either
> 0xFFFF0FF0 or 0xFFFFFFFF_FFFF0FF0, so this patch redefines them as
> (~ 32_bit_mask UL) to avoid ifdef's.
> 
> Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Suggested-by: H. Peter Anvin <hpa@...or.com>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Ok, I'm queuing it just to make sure it's not forgotten.

Thanks.
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