From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi1-f199.google.com (mail-oi1-f199.google.com [209.85.167.199]) by kanga.kvack.org (Postfix) with ESMTP id 7A05B6B7A21 for ; Thu, 6 Dec 2018 09:35:28 -0500 (EST) Received: by mail-oi1-f199.google.com with SMTP id a62so258293oii.23 for ; Thu, 06 Dec 2018 06:35:28 -0800 (PST) Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id a66si200345otb.92.2018.12.06.06.35.24 for ; Thu, 06 Dec 2018 06:35:24 -0800 (PST) Subject: Re: [PATCH V4 5/6] arm64: mm: introduce 52-bit userspace support References: <20181205164145.24568-1-steve.capper@arm.com> <20181205164145.24568-6-steve.capper@arm.com> <20181206122603.GB17473@capper-debian.cambridge.arm.com> From: Suzuki K Poulose Message-ID: Date: Thu, 6 Dec 2018 14:35:20 +0000 MIME-Version: 1.0 In-Reply-To: <20181206122603.GB17473@capper-debian.cambridge.arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Steve Capper Cc: "linux-mm@kvack.org" , "linux-arm-kernel@lists.infradead.org" , Catalin Marinas , Will Deacon , "jcm@redhat.com" , "ard.biesheuvel@linaro.org" , nd On 06/12/2018 12:26, Steve Capper wrote: > On Wed, Dec 05, 2018 at 06:22:27PM +0000, Suzuki K Poulose wrote: >> Hi Steve, >> > [...] >> I think we may need a check for the secondary CPUs to make sure that they have >> the 52bit support once the boot CPU has decided to use the feature and fail the >> CPU bring up (just like we do for the granule support). >> >> Suzuki > > Hi Suzuki, > I have just written a patch to detect a mismatch between 52-bit VA that > is being tested now. > > As 52-bit kernel VA support is coming in future, the patch checks for a > mismatch during the secondary boot path and, if one is found, prevents > the secondary from booting (and displays an error message to the user). Right now, it is the boot CPU which decides the Userspace 52bit VA, isn't it ? Irrespective of the kernel VA support, the userspace must be able to run on all the CPUs on the system, right ? So don't we need it now, with this series ? Cheers Suzuki