From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753330Ab0BZKUV (ORCPT ); Fri, 26 Feb 2010 05:20:21 -0500 Received: from mx1.redhat.com ([209.132.183.28]:31320 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751711Ab0BZKUU (ORCPT ); Fri, 26 Feb 2010 05:20:20 -0500 Message-ID: <4B87A05A.3010600@redhat.com> Date: Fri, 26 Feb 2010 12:20:10 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.7) Gecko/20100120 Fedora/3.0.1-1.fc12 Thunderbird/3.0.1 MIME-Version: 1.0 To: Joerg Roedel CC: Marcelo Tosatti , Alexander Graf , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/5] KVM: SVM: Move msrpm offset calculation to seperate function References: <1267118149-15737-1-git-send-email-joerg.roedel@amd.com> <1267118149-15737-2-git-send-email-joerg.roedel@amd.com> In-Reply-To: <1267118149-15737-2-git-send-email-joerg.roedel@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/25/2010 07:15 PM, Joerg Roedel wrote: > The algorithm to find the offset in the msrpm for a given > msr is needed at other places too. Move that logic to its > own function. > > #define MAX_INST_SIZE 15 > > @@ -417,23 +439,22 @@ err_1: > static void set_msr_interception(u32 *msrpm, unsigned msr, > int read, int write) > { > - int i; > + u8 bit_read, bit_write; > + unsigned long tmp; > + u32 offset; > > - for (i = 0; i< NUM_MSR_MAPS; i++) { > - if (msr>= msrpm_ranges[i]&& > - msr< msrpm_ranges[i] + MSRS_IN_RANGE) { > - u32 msr_offset = (i * MSRS_IN_RANGE + msr - > - msrpm_ranges[i]) * 2; > - > - u32 *base = msrpm + (msr_offset / 32); > - u32 msr_shift = msr_offset % 32; > - u32 mask = ((write) ? 0 : 2) | ((read) ? 0 : 1); > - *base = (*base& ~(0x3<< msr_shift)) | > - (mask<< msr_shift); > - return; > - } > - } > - BUG(); > + offset = svm_msrpm_offset(msr); > + bit_read = 2 * (msr& 0x0f); > + bit_write = 2 * (msr& 0x0f) + 1; > + > + BUG_ON(offset == MSR_INVALID); > + > + tmp = msrpm[offset]; > + > + read ? clear_bit(bit_read,&tmp) : set_bit(bit_read,&tmp); > + write ? clear_bit(bit_write,&tmp) : set_bit(bit_write,&tmp); > + > + msrpm[offset] = tmp; > } > This can fault - set_bit() accesses an unsigned long, which can be 8 bytes, while offset can point into the last u32 of msrpm. So this needs either to revert to u32 shift/mask ops or msrpm be changed to a ulong array (actually better, since bitmaps in general are defined as arrays of ulongs). btw, the op-level ternary expression is terrible, relying solely on *_bit()'s side effects. Please convert to an ordinary if. btw2, use __set_bit() which atomic operation is not needed. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.