From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3vHWxw4hNtzDq5W for ; Tue, 7 Feb 2017 15:46:12 +1100 (AEDT) Message-ID: <1486442760.4850.121.camel@kernel.crashing.org> Subject: Re: [RFC PATCH 5/5] powerpc/mm/hash: Increase VA range to 256TB From: Benjamin Herrenschmidt To: "Aneesh Kumar K.V" , paulus@samba.org, mpe@ellerman.id.au Cc: linuxppc-dev@lists.ozlabs.org Date: Tue, 07 Feb 2017 15:46:00 +1100 In-Reply-To: <87lgtir5wa.fsf@skywalker.in.ibm.com> References: <1486439333-22162-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1486439333-22162-6-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1486440373.4850.114.camel@kernel.crashing.org> <87lgtir5wa.fsf@skywalker.in.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 2017-02-07 at 09:47 +0530, Aneesh Kumar K.V wrote: > > Benjamin Herrenschmidt writes: > > > That's 48 bits. I would keep the limit at 47 without some explicit > > opt-in by applications. That's what users get on x86 and we know > > some GPUs have limits there. > > The idea is to have linux personality values that will limit the > effective address to different memory range. By default max effective > address will be limited to 64TB. Applications can then extend this to > 128TB or 512TB. So we will have two personality values PER_LINUX_128TB > and PER_LINUX_512TB ? No. I think we can go up to 47-bits without any personality requirement. For above, a single personality indicating that the application has no limit. Check what Intel is doing for 5-level trees Cheers, Ben.