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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9E2BFCD5BDD for ; Fri, 6 Sep 2024 11:44:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 374256B007B; Fri, 6 Sep 2024 07:44:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 324176B0082; Fri, 6 Sep 2024 07:44:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 19E516B0085; Fri, 6 Sep 2024 07:44:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id EEBB86B007B for ; Fri, 6 Sep 2024 07:43:59 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 9E09A413F5 for ; Fri, 6 Sep 2024 11:43:59 +0000 (UTC) X-FDA: 82534129398.05.2CD259A Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf18.hostedemail.com (Postfix) with ESMTP id E67761C001C for ; Fri, 6 Sep 2024 11:43:57 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=none; spf=pass (imf18.hostedemail.com: domain of cmarinas@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=cmarinas@kernel.org; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none) ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1725623012; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jlW+lt5ymLFjFq1OwMUOAB40jG76BrJeobGs1x3SCuw=; b=muF2USMnMXpiyc1n3EMZzlJTZ4bB3JB5RGjB7X+qPuvX9mCgFKDvnQN4V+w6W2PIk+Lm+a +42wL/o61UgCc9tDT92BVwa39IAyxAK1XnpmC0T5ZNyVAChs3C8FG5+mMXzINA3sccRCIL mxjQLDA4ConObkMHMqN3uFndwu5/QMc= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=none; spf=pass (imf18.hostedemail.com: domain of cmarinas@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=cmarinas@kernel.org; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none) ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1725623012; a=rsa-sha256; cv=none; b=hXiX+KS2f1gywCLw+TeL70l3FpuDTbxoIJuSJ2D/2ShNjxLOMu6uZWtCa/CZ1ixoNayLr8 qXiS5DX3Gy1FYMsKLyCt72OpxiZZqdVMUD07pXcken42nKfAC4dXT4/Buw8IxUTpGLU9v1 N2fCAkNfY4fyjckk2HFnOVpaSkocIW0= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 40C6FA44F2B; Fri, 6 Sep 2024 11:43:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AFE75C4CEC4; Fri, 6 Sep 2024 11:43:46 +0000 (UTC) Date: Fri, 6 Sep 2024 12:43:44 +0100 From: Catalin Marinas To: Arnd Bergmann Cc: guoren , Charlie Jenkins , Richard Henderson , Ivan Kokshaysky , Matt Turner , Vineet Gupta , Russell King , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , "James E . J . Bottomley" , Helge Deller , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , "David S . Miller" , Andreas Larsson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Muchun Song , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Lorenzo Stoakes , shuah , Christoph Hellwig , Michal Hocko , "Kirill A. Shutemov" , Chris Torek , Linux-Arch , linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, "linux-csky@vger.kernel.org" , loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-abi-devel@lists.sourceforge.net Subject: Re: [PATCH RFC v3 1/2] mm: Add personality flag to limit address to 47 bits Message-ID: References: <20240905-patches-below_hint_mmap-v3-0-3cd5564efbbb@rivosinc.com> <20240905-patches-below_hint_mmap-v3-1-3cd5564efbbb@rivosinc.com> <9fc4746b-8e9d-4a75-b966-e0906187e6b7@app.fastmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Stat-Signature: 5k37tpzgpeouq6s5b9xp1ycfu89zia6d X-Rspamd-Queue-Id: E67761C001C X-Rspamd-Server: rspam11 X-HE-Tag: 1725623037-728427 X-HE-Meta: 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 w7VoUWpH LNdu26Mh3/U5NwZPLUWWPFaZAH4NG94zfDfDPfkRJNa1kUYFzR4rE7LNDBRn9buDvI9390SnR6ocmzuXHpILSzyNlrajxfyqtI7/dhkFeU0x9QyGZzFhp2b3Rkx5wF61uTdNr64io7RCqW0cA41ZBL8n2kQxkL/8j+XN6rXZIyfcYmMFFs8LDzoZIcI25ibir481ueizAhUH9WVVEPnsN4d8xLuO93A65bNruwfcmbJEJNrbWyZE51iWiMZzXmWCi+pFl9JRJhZEHsBe91nF1dpCxoM9Xc7gFQrEGiUb9FLxe4U3JsKuiJW2uy5RxBRhlL+sc5CRJ9EhIZNYVTFk7iqNskNYAQ0PGFB8jE05nzUmyuYUufjiILOOf8MXrTe5kfKU2MVeycdNOs/OTkU4K2QCDmJu9EXSRw3xdhnjVVZV+3fIF4vQFi9EMQsivdong21uez3tl4++eLDEll+J1Ww99U6UU+LofEldbVni22Zekj2s= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Sep 06, 2024 at 09:55:42AM +0000, Arnd Bergmann wrote: > On Fri, Sep 6, 2024, at 09:14, Guo Ren wrote: > > On Fri, Sep 6, 2024 at 3:18 PM Arnd Bergmann wrote: > >> It's also unclear to me how we want this flag to interact with > >> the existing logic in arch_get_mmap_end(), which attempts to > >> limit the default mapping to a 47-bit address space already. > > > > To optimize RISC-V progress, I recommend: > > > > Step 1: Approve the patch. > > Step 2: Update Go and OpenJDK's RISC-V backend to utilize it. > > Step 3: Wait approximately several iterations for Go & OpenJDK > > Step 4: Remove the 47-bit constraint in arch_get_mmap_end() > > I really want to first see a plausible explanation about why > RISC-V can't just implement this using a 47-bit DEFAULT_MAP_WINDOW > like all the other major architectures (x86, arm64, powerpc64), FWIW arm64 actually limits DEFAULT_MAP_WINDOW to 48-bit in the default configuration. We end up with a 47-bit with 16K pages but for a different reason that has to do with LPA2 support (I doubt we need this for the user mapping but we need to untangle some of the macros there; that's for a separate discussion). That said, we haven't encountered any user space problems with a 48-bit DEFAULT_MAP_WINDOW. So I also think RISC-V should follow a similar approach (47 or 48 bit default limit). Better to have some ABI consistency between architectures. One can still ask for addresses above this default limit via mmap(). -- Catalin