From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932195Ab0EDNEq (ORCPT ); Tue, 4 May 2010 09:04:46 -0400 Received: from mail-pw0-f46.google.com ([209.85.160.46]:57670 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932077Ab0EDNEm (ORCPT ); Tue, 4 May 2010 09:04:42 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:in-reply-to:references:x-mailer :mime-version:content-type:content-transfer-encoding; b=RrKBMK4Q5Kcx21mtvvlYq8CQ09Nk5EMMAyB4JwH9OPRGYlXfpZu0JNdh0YWLvzMVE0 0O14uvpHPERpVUkEb3CK2VSiNqdxsT6XgRrbmzf0AJygqBIEDDrXKnweU02tYSOK1fYY 6xrCusUdYBgvN+OUNzemMU99zC6xMMYhakOP0= Date: Tue, 4 May 2010 22:04:18 +0900 From: Takuya Yoshikawa To: Takuya Yoshikawa Cc: avi@redhat.com, mtosatti@redhat.com, agraf@suse.de, yoshikawa.takuya@oss.ntt.co.jp, fernando@oss.ntt.co.jp, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, kvm-ia64@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, benh@kernel.crashing.org, paulus@samba.org, linuxppc-dev@ozlabs.org, arnd@arndb.de, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC][PATCH 7/12 not tested yet] PPC: introduce __set_bit() like function for bitmaps in user space Message-Id: <20100504220418.083929bc.takuya.yoshikawa@gmail.com> In-Reply-To: <20100504215645.6448af8f.takuya.yoshikawa@gmail.com> References: <20100504215645.6448af8f.takuya.yoshikawa@gmail.com> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.0; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org During the work of KVM's dirty page logging optimization, we encountered the need of manipulating bitmaps in user space efficiantly. To achive this, we introduce a uaccess function for setting a bit in user space following Avi's suggestion. KVM is now using dirty bitmaps for live-migration and VGA. Although we need to update them from kernel side, copying them every time for updating the dirty log is a big bottleneck. Especially, we tested that zero-copy bitmap manipulation improves responses of GUI manipulations a lot. We also found one similar need in drivers/vhost/vhost.c in which the author implemented set_bit_to_user() locally using inefficient functions: see TODO at the top of that. Probably, this kind of need would be common for virtualization area. So we introduce a function set_bit_user_non_atomic(). Signed-off-by: Takuya Yoshikawa Signed-off-by: Fernando Luis Vazquez Cao CC: Alexander Graf CC: Benjamin Herrenschmidt CC: Paul Mackerras --- arch/powerpc/include/asm/uaccess.h | 19 +++++++++++++++++++ 1 files changed, 19 insertions(+), 0 deletions(-) diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index 3a01ce8..f878326 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -321,6 +321,25 @@ do { \ __gu_err; \ }) +static inline int set_bit_user_non_atomic(int nr, void __user *addr) +{ + u8 __user *p; + u8 val; + + p = (u8 __user *)((unsigned long)addr + nr / BITS_PER_BYTE); + if (!access_ok(VERIFY_WRITE, p, 1)) + return -EFAULT; + + if (__get_user(val, p)) + return -EFAULT; + + val |= 1U << (nr % BITS_PER_BYTE); + if (__put_user(val, p)) + return -EFAULT; + + return 0; +} + /* more complex routines */ -- 1.7.0.4