From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8AA58C433FE for ; Mon, 13 Dec 2021 15:13:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=rqrlQrD6OKj+QE1hIxLxIabY2NQrA1couwCW2LY42CU=; b=yZ6cSxmgiVAsqP xvLpwhExLYf8WX2Y9E7vt7C03Qs27dgd9RfrRati+PAE9KBfr9n8tiCQSl7DK99QhT8WomSZul/sQ ch5weWmWWUNKsCTU51dGB6exe0ZPahxX5bOhRa1d4Myvl5w5nR9nr7pszCpsrsNLDW2UpXWTNSnKc Q6Z+3WUFP5HEpHjJafg2m6Q8BC0nVgujp2vtuEPGnyBX1pFJS0oLFxSTXMIgN/UOAVUu60WdsAKmd yaSLTCWpwwoMyjAR7tgpyLJ8rh+3pLJfyXl3F/MPtOZ216TDd2s8BAgZPyByutTQ6GwzPu0O3CIjw JIstUT3y+jrZFT1tB51w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mwn0z-00AIoR-MQ; Mon, 13 Dec 2021 15:13:21 +0000 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mwmYX-00A8n5-EN; Mon, 13 Dec 2021 14:43:57 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=WN0UBRQSaVnqth1lPLeu1h3m2LsiDV8FPn8ylQJCtw8=; b=p3RXvBFb2so3jcvbNtFm9YqLoy Db6NHe524T07Hi4ZiyLaxSrQxikXMESk//fQ258u8C8HwL4tvSiBf9GqWsbjwUJj0MpZb99Q3r7Gn U8I4uIl0lJmqmxhPuXIO2nSstlKIwd5Iq6DRxuuB+XewafpJUhhMkxy8nn3Di3UE6QlKKR/tkzwqN 82AY01mLzM89zRBTPtsel1HfkWhp0iwheQwoshPsb7I7IaBR/GEnNFzI6tMIojo9QsGW9FNyl0q0u 8cNlSbM2lT2wank3wbXnRWxj4TWJs6JahqJ/E/e+nJSdtlRCOOK0S/1TpqDLQhR1BBCV9fSEeWv7a TVTjir2Q==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mwmYS-00Csn8-Vy; Mon, 13 Dec 2021 14:43:53 +0000 Date: Mon, 13 Dec 2021 14:43:52 +0000 From: Matthew Wilcox To: David Laight Cc: 'Tiezhu Yang' , Dave Young , Baoquan He , Vivek Goyal , Andrew Morton , "linux-arm-kernel@lists.infradead.org" , "linux-ia64@vger.kernel.org" , "linux-mips@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-riscv@lists.infradead.org" , "linux-sh@vger.kernel.org" , "x86@kernel.org" , "linux-fsdevel@vger.kernel.org" , "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Xuefeng Li Subject: Re: [PATCH v2 0/2] kdump: simplify code Message-ID: References: <1639193588-7027-1-git-send-email-yangtiezhu@loongson.cn> <0c5cb37139af4f3e85cc2c5115d7d006@AcuMS.aculab.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Mon, Dec 13, 2021 at 08:30:33AM +0000, David Laight wrote: > From: Matthew Wilcox > > Sent: 12 December 2021 11:48 > > > > On Sat, Dec 11, 2021 at 05:53:46PM +0000, David Laight wrote: > > > From: Tiezhu Yang > > > > Sent: 11 December 2021 03:33 > > > > > > > > v2: > > > > -- add copy_to_user_or_kernel() in lib/usercopy.c > > > > -- define userbuf as bool type > > > > > > Instead of having a flag to indicate whether the buffer is user or kernel, > > > would it be better to have two separate buffer pointers. > > > One for a user space buffer, the other for a kernel space buffer. > > > Exactly one of the buffers should always be NULL. > > > > No. You should be using an iov_iter instead. See > > https://lore.kernel.org/all/Ya4bdB0UBJCZhUSo@casper.infradead.org/ > > for a start on this. > > iov_iter gets horribly expensive... Oh, right. Reading the kcore is a high-performance path, my mistake. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv