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Re: [Xen-devel] [PATCH] [x86_64] Fixing PGT_va_mutable and PGT_va_unknow

To: "Nakajima, Jun" <jun.nakajima@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] [x86_64] Fixing PGT_va_mutable and PGT_va_unknown
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Mon, 15 Aug 2005 08:48:19 +0100
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On 15 Aug 2005, at 08:50, Nakajima, Jun wrote:

Okay, but I see no reason to change PGT_va_mask. You already include
28 bits where you actually need only 27 bits of backptr.

The current one
#define PGT_va_mask         ((unsigned long)((1U<<28)-1)<<PGT_va_shift)
includes only 27 bits (see -1).

(1<<n)-1 sets the n least significant bits, not n-1.

 -- Keir


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