Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753374AbbF3N60 (ORCPT ); Tue, 30 Jun 2015 09:58:26 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:43578 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752637AbbF3N6S (ORCPT ); Tue, 30 Jun 2015 09:58:18 -0400 Message-ID: <5592A076.8090603@codeaurora.org> Date: Tue, 30 Jun 2015 08:58:14 -0500 From: Timur Tabi User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:36.0) Gecko/20100101 Firefox/36.0 SeaMonkey/2.33.1 MIME-Version: 1.0 To: Will Deacon CC: Catalin Marinas , "abhimany@codeaurora.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "sboyd@codeaurora.org" Subject: Re: [PATCH] ARM64: TTY: hvc_dcc: Add support for ARM64 dcc References: <1434751734-2178-1-git-send-email-timur@codeaurora.org> <20150622131228.GE1583@arm.com> <558B0EEC.9040504@codeaurora.org> <20150630135153.GJ27725@arm.com> In-Reply-To: <20150630135153.GJ27725@arm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1693 Lines: 45 Will Deacon wrote: > Well, it's up to you to figure out the details, but I'd start by adding > some static inlines to the arch-specific header files for enabling/disabling > userspace access. > > From there, I think I'd get the architecture init code to reset the thing > to "disabled" (so it's disabled regardless of whether we build the hvc_dcc > driver) and then if you wanted to go all-out, we could have a sysfs entry > provided by the driver to toggle it on and off. > >> >static int __init hvc_dcc_console_init(void) >> >{ >> >#ifdef CONFIG_ARM64 >> > u32 val; >> > >> > asm("msr mdscr_el1, %0 " >> > "orr %0, %0, #4096 " /* TDCC */ >> > "msr %0, mdscr_el1 " >> > : "=r" (val)); >> >#endif >> > >> >But this seems clunky. > Yeah, that's super ugly. > >> >I am concerned about KVM, though. There appears to be code in KVM in >> >hyp.s and sys_regs.c that touches and/or emulates MDSCR_EL1. >> > >> >On a side note, it does not appear that ARM32 blocks userspace DCC. I >> >don't see where DBGDSCR.UDCCdis is set. > That's a bug imo. So wouldn't it be more appropriate to have a separate patch that handles disabling of user-space DCC for ARM32 and ARM64? All I really want to do at this point is provide basic DCC support for ARM64, just like we have for ARM32. -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/