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 F2864C4706C for ; Sat, 13 Jan 2024 17:28:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 656376B0089; Sat, 13 Jan 2024 12:28:07 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6082C6B008C; Sat, 13 Jan 2024 12:28:07 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4CE176B0092; Sat, 13 Jan 2024 12:28:07 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 3EA776B0089 for ; Sat, 13 Jan 2024 12:28:07 -0500 (EST) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 13EB6C013E for ; Sat, 13 Jan 2024 17:28:07 +0000 (UTC) X-FDA: 81674971014.16.7876050 Received: from out162-62-57-210.mail.qq.com (out162-62-57-210.mail.qq.com [162.62.57.210]) by imf23.hostedemail.com (Postfix) with ESMTP id 73AF7140014 for ; Sat, 13 Jan 2024 17:28:02 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=qq.com header.s=s201512 header.b=ukzssRAC; spf=none (imf23.hostedemail.com: domain of cyy@cyyself.name has no SPF policy when checking 162.62.57.210) smtp.mailfrom=cyy@cyyself.name; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1705166883; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=9n72WKKKGYhqMdswP9Jj7VEaJwHs3IyzRS4xEll9rYI=; b=3TeFhwavi3TrgbCc1bEGHO6+dhdspU3aDkDCck/efenQt5LlNVvJVonuFcl/fbxDqUgO4v emA7BGqXRx2WOXPBPlozp/q30omO8fzwX4glz/whD4NXioDxt//kS2RkTGddHKPIoHf3AW 7EOzCd7WqFDXcb/Vhvl7SfDHswcpcnM= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1705166883; a=rsa-sha256; cv=none; b=nRpXElzNb8gFgS+YAaUJA6hcC8h6fU7JzVBvXWLXRbRwUV8N3bJVvqDfPjYDE5SiWO6N0O FERHEy98pMKZeESw4YdzSaTfsNlx6307YvE4EvFIdGQuoEVOVBEdMZPF8gm9cXglwFoSGo Mlg4psWaF30RA2nnzOdgBITWAQK4wFw= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=qq.com header.s=s201512 header.b=ukzssRAC; spf=none (imf23.hostedemail.com: domain of cyy@cyyself.name has no SPF policy when checking 162.62.57.210) smtp.mailfrom=cyy@cyyself.name; dmarc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=qq.com; s=s201512; t=1705166867; bh=9n72WKKKGYhqMdswP9Jj7VEaJwHs3IyzRS4xEll9rYI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ukzssRACnz3BFOQ4m0PrtOBC+c3ULmzJzKNt2HiTP2zC7dzmPLW+FHncUgy76IUE4 bBSFdgBVxfqt3ilig5ltgbGZKNlqBnwvrADPa0YP4lfB4HrJGDn5rUl3BbiJvb9e3P f5Md6MBUvXZU9MQybaI0l9rZ76Crk8hUiMtlUkkE= Received: from cyy-pc.lan ([218.70.255.58]) by newxmesmtplogicsvrszc5-1.qq.com (NewEsmtp) with SMTP id 6B9BD474; Sun, 14 Jan 2024 01:26:57 +0800 X-QQ-mid: xmsmtpt1705166817tpw8s6zxo Message-ID: X-QQ-XMAILINFO: MpYZqmNm/7vMFQChzuZcNMPEZCicAYxwA3bgPt5oBo3Izruh5SDSD1/vjfZIJe 7IBevBAJJvXhgU9B+SMnjtsigosK99wXz45XosSRmglerB4jvY07z2ypp/fWsmUwQLZ3rc4lgw08 0I7c4e9ssoe0Ldzh7aDfnOwg3ItEwflH/BF3rnY12bJD7xRo/M9ZSFqZABHgOKsvejN9E8BhUm2D boo2oTfkaKEQcLeunqTCbSyoFYN07nmPJtRl8ODOOCFEIFDrcTWZHY0wX7tuAYx6PuS1SJSjXYS2 bOEVhUBovGWI01NTW0yrPLyhFe33CdafAdJAf1SrjfgmRNyBqHdsDLZz7UlH9vHjFxvMrmU3dy5N 45B3OLgeNOTV6WEfUAL3IRazwMFr8aKB9LH+gkUjByXzXtwcrFHxXmMsjpssUiAlF1duH66p4Avr 84W1XexcvjfBXHBgXn5BFW2+ogGmclzTetljdN04BAku6PGLStHt7Vs8LRhxh82ARYq6o+Md+kgL NJxin6UVnpDBzYjg39bVX6PvJK3U699wPbe+uQtu79mMUgZ8WzO3iGxiOmirlrq0y8rVSXD7t5iM GYsxJ8FGK+3+d6K/ILCMvSeHJKdwbCtWTtAdunvZubJwOzaynOeC1geHeMxH34ZZztsMnz79vLpe YGChZ7mLTbp5fUDptY+VCdcdL4Fy7KWDgIBg7MTpy9RLjNazovEqG5960r71+VO+2pza3/A/dviG n0++0sT/QAFpxAF7w8YGMItABROQoWSr+xES2srhGGf311gs4BzoOgOKZhvP5I3hexb4JG++/Bt2 OrIfwjVtIS7Tr5jYRQvXT+uKYpMsexCp3J8Xip53EB0io7BHq+H8zipn5FRMnuzONGJrAQAd9WC+ I81SztmB19m/xMFkY6qEQ5yrj6ENCd3r8gON2zNjMQDmvw7Tdjfni3yzimGkBOehL2PYtcjs/KFk RJDRSTS7yAifSWQWUnc3KxIF9qzMRd X-QQ-XMRINFO: NyFYKkN4Ny6FSmKK/uo/jdU= From: Yangyu Chen To: charlie@rivosinc.com Cc: alexghiti@rivosinc.com, anup@brainfault.org, aou@eecs.berkeley.edu, conor@kernel.org, jrtc27@jrtc27.com, konstantin@linuxfoundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, mick@ics.forth.gr, palmer@rivosinc.com, paul.walmsley@sifive.com, rdunlap@infradead.org Subject: Re: [PATCH v10 0/4] RISC-V: mm: Make SV48 the default address space Date: Sun, 14 Jan 2024 01:26:57 +0800 X-OQ-MSGID: <20240113172657.997104-1-cyy@cyyself.name> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20230809232218.849726-1-charlie@rivosinc.com> References: <20230809232218.849726-1-charlie@rivosinc.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 73AF7140014 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: ibk5t8naec8p15ejs1xebc3rz79bc117 X-HE-Tag: 1705166882-244122 X-HE-Meta: U2FsdGVkX1+juERsRROhkchid+cd44zwooR0OtXt8P1jsLX8wW6BleiYbEwhj49t9NqLlkebYUD4DN/l7ydmuHFRJD7X+7u9z3g0kA2At+Gxy4IY9A0UtkUrXHPe8k24lsZ4CWqd0/22dXHb9dP8ea/H5OMAdDt21EfLQ6ilZYvZju3m+n3B9pWe1uxhqM/cU7GyNhZFYoC1dFLzNYOYz5BdKNou855/AgbRztOxY6NcfeOUxHJ+l8zOvCjDujNp8P3UP21sFJoYKdw/Ehe4ow8Kwq84YLE3zqNdAi6Za34SarYS2PAxKbowLsYP8MMc4MCKKM57wo7shgZjL5sQIbWcShknBQH1Jf2+W8GnBSVffG49geyfsZkFHyQmxw3L38/4RYXNTAcfRgiGQNO8LuyB/zIGWQriKSyxpKgfCyIZxa+ekPUo/gH21j2AKO49a1XRBOwdKHb2q4DGQPrXzFA+vosIZBsClZW2xoVn20LnDeEGbL7u8EKTh+Br5qOdMJCtXmT2iWmVAZsQBxzlX9DnijWC/0bjvBcN9s4/Zcy9qsGGdBe2V85nmCP6lfWGIzgozhWCoy1l8C3fyM+YZhPCYxMU0UCrLK8ZhJlEy6QuZVI085wFq2qg1FwO1Bti32a4DZZItqHC9otuZ+ePddy/v81mUUMECLDaJRWUwD8KIGmnO2XitkqYx5UwisxFfkm6jWZ453uyR1zKQEK487+U7hqNchCtlL96YnkNyU+MWleuJJTPHmj88qEJYcEUK0sb1V3AJZiSanEf6bzIeL62IYnO4ZG6WKtYMtfVQFezSrqupzhNhVhlbQ7PgE0cgJRkxtqJQaPu+MCKh9FEsL2+cnKEknF119z53TDsf/DDCaQvCDQF+lN5h+/IWqwwlOPlDvA1Z/RzEMa3XMt8X6k9t4BRz6iGcnquHYPZt2h4PuewxMfYB3CtlAzqYWooMz6EhSs91UdCyMv4zrz UYA24PWN y0wLBT3yEuSqGCSiXnLScHwkjGr6Pop9ExcBEUY+HZCIGQDv3QmR/NkgOpg/PSyPBB38gFfV+XW03tmnflhppjLdrxcMzsHsb2izx X-Bogosity: Ham, tests=bogofilter, spamicity=0.000076, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi, Charlie Although this patchset has been merged I still have some questions about this patchset. Because it breaks regular mmap if address >= 38 bits on sv48 / sv57 capable systems like qemu. For example, If a userspace program wants to mmap an anonymous page to addr=(1<<45) on an sv48 capable system, it will fail and kernel will mmaped to another sv39 address since it does not meet the requirement to use sv48 as you wrote: > else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \ > mmap_end = VA_USER_SV48; \ > else \ > mmap_end = VA_USER_SV39; \ Then, How can a userspace program create a mmap with a hint if the address >= (1<<38) after your patch without MAP_FIXED? The only way to do this is to pass a hint >= (1<<47) on mmap syscall then kernel will return a random address in sv48 address space but the hint address gets lost. I think this violate the principle of mmap syscall as kernel should take the hint and attempt to create the mapping there. I don't think patching in this way is right. However, if we only revert this patch, some programs relying on mmap to return address with effective bits <= 48 will still be an issue and it might expand to other ISAs if they implement larger virtual address space like RISC-V sv57. A better way to solve this might be adding a MAP_48BIT flag to mmap like MAP_32BIT has been introduced for decades. Thanks, Yangyu Chen