From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Date: Fri, 23 Apr 2010 13:20:36 +0000 Subject: Re: [PATCH RFC v2 6/6] KVM: introduce a new API for getting dirty Message-Id: <4BD19EA4.4080208@redhat.com> List-Id: References: <20100420200353.2d2a6dec.yoshikawa.takuya@oss.ntt.co.jp> In-Reply-To: <20100420200353.2d2a6dec.yoshikawa.takuya@oss.ntt.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kvm-ia64@vger.kernel.org On 04/23/2010 03:59 PM, Alexander Graf wrote: > >> Ah so the 31st bit is optional as far as userspace is concerned? What does it mean? (just curious) >> > The 0x80000000 bit declares that a pointer is in 24-bit mode, so that applications can use the spare upper bits for random data. > > See http://en.wikipedia.org/wiki/31-bit for an explanation. > Interesting. Luckily AMD made the top 16 bits of pointers reserved in x86-64. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.