From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 1/2] KVM: Remove unnecessary divide operations Date: Thu, 01 Jul 2010 17:18:13 +0300 Message-ID: <4C2CA3A5.2040802@redhat.com> References: <1277992812-31945-1-git-send-email-joerg.roedel@amd.com> <1277992812-31945-2-git-send-email-joerg.roedel@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Joerg Roedel Return-path: Received: from mx1.redhat.com ([209.132.183.28]:27819 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754546Ab0GAOSV (ORCPT ); Thu, 1 Jul 2010 10:18:21 -0400 In-Reply-To: <1277992812-31945-2-git-send-email-joerg.roedel@amd.com> Sender: kvm-owner@vger.kernel.org List-ID: On 07/01/2010 05:00 PM, Joerg Roedel wrote: > This patch converts unnecessary divide and modulo operations > in the KVM large page related code into logical operations. > This allows to convert gfn_t to u64 while not breaking 32 > bit builds. > > > #define KVM_NR_PAGE_SIZES 2 > -#define KVM_HPAGE_SHIFT(x) (PAGE_SHIFT + ((x) - 1) * 8) > +#define KVM_HPAGE_GFN_SHIFT(x) (((x) - 1) * 8) > +#define KVM_HPAGE_SHIFT(x) (PAGE_SHIFT + KVM_HPAGE_GFN_SHIFT(x)) > #define KVM_HPAGE_SIZE(x) (1UL<< KVM_HPAGE_SHIFT(x)) > #define KVM_HPAGE_MASK(x) (~(KVM_HPAGE_SIZE(x) - 1)) > In theory, KVM_HPAGE_SIZE() needs s/1UL/(u64)1/, or KVM_HPAGE_MASK becomes truncated if used against a gfn_t. In practice, KVM_HPAGE_MASK is not used at all, so this doesn't matter. -- error compiling committee.c: too many arguments to function