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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 A522BC4360C for ; Wed, 2 Oct 2019 20:30:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83595207FF for ; Wed, 2 Oct 2019 20:30:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728113AbfJBUa5 (ORCPT ); Wed, 2 Oct 2019 16:30:57 -0400 Received: from avon.wwwdotorg.org ([104.237.132.123]:44176 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725799AbfJBUa4 (ORCPT ); Wed, 2 Oct 2019 16:30:56 -0400 Received: from [10.20.204.51] (unknown [216.228.112.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by avon.wwwdotorg.org (Postfix) with ESMTPSA id 1D3BD1C00ED; Wed, 2 Oct 2019 14:30:55 -0600 (MDT) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.100.3 at avon.wwwdotorg.org Subject: Re: [PATCH] arm64: tegra: only map accessible sysram To: Mian Yousaf Kaukab Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, treding@nvidia.com, jonathanh@nvidia.com, linux-tegra@vger.kernel.org References: <20190929200851.14228-1-ykaukab@suse.de> <5d2e47ec-8304-d648-9c4a-80c7c02050a9@wwwdotorg.org> <20190930100212.GA21324@suse.de> From: Stephen Warren Message-ID: Date: Wed, 2 Oct 2019 14:30:53 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190930100212.GA21324@suse.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/30/19 4:02 AM, Mian Yousaf Kaukab wrote: > On Sun, Sep 29, 2019 at 11:28:43PM -0600, Stephen Warren wrote: >> On 9/29/19 2:08 PM, Mian Yousaf Kaukab wrote: >>> Most of the SysRAM is secure and only accessible by TF-A. >>> Don't map this inaccessible memory in kernel. Only map pages >>> used by bpmp driver. >> >> I don't believe this change is correct. The actual patch doesn't >> implement mapping a subset of the RAM (a software issue), but rather it >> changes the DT representation of the SYSRAM hardware. The SYSRAM >> hardware always does start at 0x30000000, even if a subset of the >> address range is dedicated to a specific purpose. If the kernel must map >> only part of the RAM, then some additional property should indicate >> this.[...] > I agree the hardware description becomes inaccurate with this change. > > In the current setup complete 0x3000_0000 to 0x3005_0000 range is being mapped > as normal memory (MT_NORMAL_NC). Though only 0x3004_E000 to 0x3005_0000 are > accessible by the kernel. Nit: I expect that a much larger region than that is *accessible*, although it's quite plausible that only that region is actually *accessed*/used right now. > I am seeing an issue where a read access (which I > believe is speculative) to inaccessible range causes an SError. Another > solution for this problem could be to add "no-memory-wc" to SysRAM node so that > it is mapped as device memory (MT_DEVICE_nGnRE). Would that be acceptable? Why does the driver blindly map the entire memory at all? Surely it should only map the portions of RAM that other drivers request/use? And surely the BPMP driver or DT node is already providing that information? But yes, changing the mapping type to avoid speculation might be an acceptable solution for now, although I think we'd want to work things out better later. I don't know if there would be any impact to the BPMP driver related to the slower SRAM access due to this change. Best consult a BPMP expert or Tegra maintainer about that. >> [...] Also, I believe it's incorrect to hard-code into the kernel's DT >> the range of addresses used by the secure monitor/OS, since this can >> vary depending on what the user actually chooses to install as the >> secure monitor/OS. Any indication of such regions should be filled in at >> runtime by some boot firmware or the secure monitor/OS itself, or >> retrieved using some runtime API rather than DT. > Secure-OS addresses are not of interest here. SysRAM is partitioned > between secure-OS and BPMP and kernel is only interested in the BPMP > part. The firmware can update these addresses in the device-tree if it > wants to. Would you prefer something similar implemented in u-boot so > that it updates SysRAM node to only expose kernel accessible part of it > to the kernel? > > Can u-boot dynamically figure out the Secure-OS vs BPMP partition? > > BR, > Yousaf >