From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751855AbeAQC66 (ORCPT + 1 other); Tue, 16 Jan 2018 21:58:58 -0500 Received: from szxga07-in.huawei.com ([45.249.212.35]:48870 "EHLO huawei.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750811AbeAQC65 (ORCPT ); Tue, 16 Jan 2018 21:58:57 -0500 Subject: Re: [PATCH v3 06/20] arm64: mm: Fix and re-enable ARM64_SW_TTBR0_PAN To: Will Deacon , References: <1512563739-25239-1-git-send-email-will.deacon@arm.com> <1512563739-25239-7-git-send-email-will.deacon@arm.com> CC: , , , , , , , , , , Xiexiuqi From: Yisheng Xie Message-ID: Date: Wed, 17 Jan 2018 10:58:23 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <1512563739-25239-7-git-send-email-will.deacon@arm.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.29.40] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: Hi Will, On 2017/12/6 20:35, Will Deacon wrote: > config ARM64_SW_TTBR0_PAN > bool "Emulate Privileged Access Never using TTBR0_EL1 switching" > - depends on BROKEN # Temporary while switch_mm is reworked > help > Enabling this option prevents the kernel from accessing > user-space memory directly by pointing TTBR0_EL1 to a reserved I have a question not related to this patch itself, but to ARM64_SW_TTBR0_PAN: What does ARM64_SW_TTBR0_PAN used for? I means is hardware support PAN, do we still need SW_TTBR0_PAN? And if the hardware do not support PAN, is SW_TTBR0_PAN is *must* option? or there maybe a security risk? Thanks Yisheng Xie From mboxrd@z Thu Jan 1 00:00:00 1970 From: xieyisheng1@huawei.com (Yisheng Xie) Date: Wed, 17 Jan 2018 10:58:23 +0800 Subject: [PATCH v3 06/20] arm64: mm: Fix and re-enable ARM64_SW_TTBR0_PAN In-Reply-To: <1512563739-25239-7-git-send-email-will.deacon@arm.com> References: <1512563739-25239-1-git-send-email-will.deacon@arm.com> <1512563739-25239-7-git-send-email-will.deacon@arm.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Will, On 2017/12/6 20:35, Will Deacon wrote: > config ARM64_SW_TTBR0_PAN > bool "Emulate Privileged Access Never using TTBR0_EL1 switching" > - depends on BROKEN # Temporary while switch_mm is reworked > help > Enabling this option prevents the kernel from accessing > user-space memory directly by pointing TTBR0_EL1 to a reserved I have a question not related to this patch itself, but to ARM64_SW_TTBR0_PAN: What does ARM64_SW_TTBR0_PAN used for? I means is hardware support PAN, do we still need SW_TTBR0_PAN? And if the hardware do not support PAN, is SW_TTBR0_PAN is *must* option? or there maybe a security risk? Thanks Yisheng Xie