From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 54EBE2DECDF for ; Mon, 20 Jul 2026 17:34:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=96.67.55.147 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784568896; cv=none; b=q7czsPUpdZAotKspTheD2TXxdBBP/Rst31G85qIvX8zcnfFvTFQdZ9hactJaxiIrQRktSXZc/DFFdPZeuzxR8hLJR7GJaZ2CirKTjTzDWFI77jcrqS74lueex+Up96FldhsvZbpFxfWD3fsB03niBBP4dWCiw7JPx6vU5eF4ynE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784568896; c=relaxed/simple; bh=lqDry25wj7TSbFW5ERvxLx9KACpzecKRYOZakJ+uobk=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=g/yM4v8X/LAyh8Uk2ANvQ0C9RstPHrDOWSO6CbhE7e8VkAy8XI7YytxC2mDT00+fyHbx4HgN6UfiB0eig7rPkl+vEDJpPYt83XyxbJsIdqarzGKfM/QwHKH8x5OVShkblljeJrmk9znap0kNVNQWTbOmRlU45DBVsdY9zRG4pno= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com; spf=pass smtp.mailfrom=surriel.com; dkim=pass (2048-bit key) header.d=surriel.com header.i=@surriel.com header.b=Sp87H45c; arc=none smtp.client-ip=96.67.55.147 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=surriel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=surriel.com header.i=@surriel.com header.b="Sp87H45c" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=surriel.com ; s=mail; h=MIME-Version:Content-Transfer-Encoding:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=VpgEGbQd7TUjFEcy4MwyOPp2fSwSzsT74h5eZuIrKNc=; b=Sp87H45crDR89XUlafK04T1y/o I/b/2NpEeAeRnQBadvGb72DkxwlguQl6tUofmiDsjeo5mO/LWih1G6hnM7Z+lEARQGQ+RJPXRNdtv T+qYaVKqv6P0ymHqoZJxZ2NsfuKXkSGiuEh5FnXzLK6BTcK/6+ozaV+vbG2VIbqZxjMEKEuiUPyaZ qfaI2NHjMIz8HQ4xMWNT96PZUDFAGvlnX9dvR9YcBPSbitfgdzv4jTscRR53wthhZTdPUkeCxsK8O pZTPHyLxLMiNK5IFk81GPB93l4sWHbvjCVXCuGG+D2uNfCmeXTYdvQ+1xluzEuJq1iZaEc+jTLi5b H2ezgwrA==; Received: from fangorn.home.surriel.com ([10.0.13.7]) by shelob.surriel.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.97.1) (envelope-from ) id 1wlrt1-00000000359-185o; Mon, 20 Jul 2026 13:34:39 -0400 Message-ID: <51c0025d2eb885ff1f4775e4d9ffcf34f478f378.camel@surriel.com> Subject: Re: [PATCH RFC v3 2/6] riscv/mm: add untagged_addr_remote_unlocked() From: Rik van Riel To: Usama Arif Cc: linux-kernel@vger.kernel.org, Andrew Morton , kernel-team@meta.com, David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , linux-riscv@lists.infradead.org Date: Mon, 20 Jul 2026 13:34:39 -0400 In-Reply-To: <46dc1b58-f2de-492a-9da5-a5c429c19a10@linux.dev> References: <20260720115741.239657-1-usama.arif@linux.dev> <13ec2603d5cbfdc493939f182b71e5133c26af54.camel@surriel.com> <46dc1b58-f2de-492a-9da5-a5c429c19a10@linux.dev> Autocrypt: addr=riel@surriel.com; prefer-encrypt=mutual; keydata=mQENBFIt3aUBCADCK0LicyCYyMa0E1lodCDUBf6G+6C5UXKG1jEYwQu49cc/gUBTTk33A eo2hjn4JinVaPF3zfZprnKMEGGv4dHvEOCPWiNhlz5RtqH3SKJllq2dpeMS9RqbMvDA36rlJIIo47 Z/nl6IA8MDhSqyqdnTY8z7LnQHqq16jAqwo7Ll9qALXz4yG1ZdSCmo80VPetBZZPw7WMjo+1hByv/ lvdFnLfiQ52tayuuC1r9x2qZ/SYWd2M4p/f5CLmvG9UcnkbYFsKWz8bwOBWKg1PQcaYHLx06sHGdY dIDaeVvkIfMFwAprSo5EFU+aes2VB2ZjugOTbkkW2aPSWTRsBhPHhV6dABEBAAG0HlJpayB2YW4gU mllbCA8cmllbEByZWRoYXQuY29tPokBHwQwAQIACQUCW5LcVgIdIAAKCRDOed6ShMTeg05SB/986o gEgdq4byrtaBQKFg5LWfd8e+h+QzLOg/T8mSS3dJzFXe5JBOfvYg7Bj47xXi9I5sM+I9Lu9+1XVb/ r2rGJrU1DwA09TnmyFtK76bgMF0sBEh1ECILYNQTEIemzNFwOWLZZlEhZFRJsZyX+mtEp/WQIygHV WjwuP69VJw+fPQvLOGn4j8W9QXuvhha7u1QJ7mYx4dLGHrZlHdwDsqpvWsW+3rsIqs1BBe5/Itz9o 6y9gLNtQzwmSDioV8KhF85VmYInslhv5tUtMEppfdTLyX4SUKh8ftNIVmH9mXyRCZclSoa6IMd635 Jq1Pj2/Lp64tOzSvN5Y9zaiCc5FucXtB9SaWsgdmFuIFJpZWwgPHJpZWxAc3VycmllbC5jb20+iQE +BBMBAgAoBQJSLd2lAhsjBQkSzAMABgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRDOed6ShMTe g4PpB/0ZivKYFt0LaB22ssWUrBoeNWCP1NY/lkq2QbPhR3agLB7ZXI97PF2z/5QD9Fuy/FD/jddPx KRTvFCtHcEzTOcFjBmf52uqgt3U40H9GM++0IM0yHusd9EzlaWsbp09vsAV2DwdqS69x9RPbvE/Ne fO5subhocH76okcF/aQiQ+oj2j6LJZGBJBVigOHg+4zyzdDgKM+jp0bvDI51KQ4XfxV593OhvkS3z 3FPx0CE7l62WhWrieHyBblqvkTYgJ6dq4bsYpqxxGJOkQ47WpEUx6onH+rImWmPJbSYGhwBzTo0Mm G1Nb1qGPG+mTrSmJjDRxrwf1zjmYqQreWVSFEt26tBpSaWsgdmFuIFJpZWwgPHJpZWxAZmIuY29tP okBPgQTAQIAKAUCW5LbiAIbIwUJEswDAAYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQznneko TE3oOUEQgAsrGxjTC1bGtZyuvyQPcXclap11Ogib6rQywGYu6/Mnkbd6hbyY3wpdyQii/cas2S44N cQj8HkGv91JLVE24/Wt0gITPCH3rLVJJDGQxprHTVDs1t1RAbsbp0XTksZPCNWDGYIBo2aHDwErhI omYQ0Xluo1WBtH/UmHgirHvclsou1Ks9jyTxiPyUKRfae7GNOFiX99+ZlB27P3t8CjtSO831Ij0Ip QrfooZ21YVlUKw0Wy6Ll8EyefyrEYSh8KTm8dQj4O7xxvdg865TLeLpho5PwDRF+/mR3qi8CdGbkE c4pYZQO8UDXUN4S+pe0aTeTqlYw8rRHWF9TnvtpcNzZw== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2026-07-20 at 17:46 +0100, Usama Arif wrote: >=20 >=20 > On 20/07/2026 16:08, Rik van Riel wrote: > > On Mon, 2026-07-20 at 04:57 -0700, Usama Arif wrote: > > > On Fri, 17 Jul 2026 13:00:32 -0400 Rik van Riel > > > > > > wrote: > > >=20 > > >=20 > > > >=20 > > > > mm->context.pmlen is set only through PR_SET_TAGGED_ADDR_CTRL > > > > and > > > > is stable > > > > afterwards, so it can be read without the mmap lock, as it > > > > already > > > > is from > > > > untagged_addr() and mm_untag_mask(). > > > >=20 > > >=20 > > > I think it might not be stable? set_tagged_addr_ctrl() can change > > > it > > > repeatedly until a CLONE_VM operation sets MM_CONTEXT_LOCK_PMLEN. > >=20 > > You're right, ARM tagged addresses seem to work a >=20 > ah do you mean RISCV here? Ugh, I looked at the wrong one. RISCV is like x86, with a dynamic (though a limited number of options?) mask. Having said that, won't a process have all of its VMAs in the masked-off area, so coming in from a remote process to a valid memory address should already give us a valid address? --=20 All Rights Reversed.