From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH RFC v2 6/6] KVM: introduce a new API for getting dirty bitmaps Date: Fri, 23 Apr 2010 16:20:36 +0300 Message-ID: <4BD19EA4.4080208@redhat.com> References: <20100420195349.dab60b1d.yoshikawa.takuya@oss.ntt.co.jp> <201004231427.30725.arnd@arndb.de> <4BD195B7.3070409@redhat.com> <201004231446.07880.arnd@arndb.de> <4BD19831.5000405@redhat.com> <9557F344-EC7C-450F-AED9-5BB865C08650@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Arnd Bergmann , =?UTF-8?B?RmVybmFuZG8gTHVpcyBWw6F6cXVl?= =?UTF-8?B?eiBDYW8=?= , Takuya Yoshikawa , mtosatti-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kvm-ia64-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kvm-ppc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Alexander Graf Return-path: In-Reply-To: <9557F344-EC7C-450F-AED9-5BB865C08650-l3A5Bk7waGM@public.gmane.org> Sender: kvm-ppc-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: kvm.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.