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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0D8B8C43381 for ; Wed, 27 Mar 2019 07:54:45 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 9D0E020811 for ; Wed, 27 Mar 2019 07:54:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="LUeo46j6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D0E020811 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=DP24AZQ1tyIxe2EKC/oMuUUZZbAeFch7qP7GYSoZT9g=; b=LUeo46j6BxO1rI JTw0y/A+dAJlLTkW2FehqVykLI27lxOk7hyKOWF8bMmQ0mpEOboLbnYRyxlHRFYkk4CoS25v2EHMG 7Ga3h37m2Lc1+SYpkmef9Hx3Ns2b6q6F7GqUrxf51bkdEA1T/1EiHihU/oWlMI5PafY3Bxpohu+QE EvtYdHPTGdS8h9Rei1stSg37GJS5i91v90DM2u9ArSCYbNcAmgJwywnxzZiCJE8J3nywSD6V2OIXj sCngwF6HeH3zaHt9dTUjXTq4QiJ/An/lsnd34JxzYlsMIDW0+t+bVpexyzNZLDSudQe5jHEFMlX+q uInvWsNILr2rJPQ3qUpw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h93OV-0001Dm-S8; Wed, 27 Mar 2019 07:54:43 +0000 Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1h93OT-0001DD-Fo; Wed, 27 Mar 2019 07:54:41 +0000 Date: Wed, 27 Mar 2019 00:54:41 -0700 From: Christoph Hellwig To: Anup Patel Subject: Re: [PATCH v3 4/4] RISC-V: Allow booting kernel from any 4KB aligned address Message-ID: <20190327075441.GA29894@infradead.org> References: <20190325092234.5451-1-anup.patel@wdc.com> <20190325092234.5451-5-anup.patel@wdc.com> <20190325113935.GD27843@infradead.org> <20190325145919.GB14826@infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Palmer Dabbelt , Anup Patel , "linux-kernel@vger.kernel.org" , Mike Rapoport , Christoph Hellwig , Atish Patra , Albert Ou , Paul Walmsley , "linux-riscv@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org On Mon, Mar 25, 2019 at 09:46:59PM +0530, Anup Patel wrote: > > Why do you even care about kernel mappings for non-existant ram. > > We care because there will always be some buggy kernel driver/code going > out-of-bound and accessing non-existent RAM. If we by default map all > possible kernel virtual address then behaviour of buggy accesses will be > unpredictable. > > Further, I think we should also make .text and .rodata sections of kernel > as read-only. This will protect kernel code and rodata. All of that is useful at the final_setup_vm() time - but none of it matters during early setup_vm where life is complicated. Mike suggested on the previous iteration that you only do smaller mappings when setting up the final mapping to avoid the ops churn, and I fully agree with him. So I would suggest we avoid complicated the fiddly early boot changes that just add complxity, and you instead redirect your efforts to say implemented proper ro and non-executable sections using 4k mappings in the final VM setup only. That should actuall lead to less code and complexity, and provide more benefits. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv