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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9077C433E0 for ; Thu, 25 Jun 2020 17:16:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A1CC620707 for ; Thu, 25 Jun 2020 17:16:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A1CC620707 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3D79A6B0093; Thu, 25 Jun 2020 13:16:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3AEBA8D000C; Thu, 25 Jun 2020 13:16:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2C3C58D000B; Thu, 25 Jun 2020 13:16:08 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0235.hostedemail.com [216.40.44.235]) by kanga.kvack.org (Postfix) with ESMTP id 15F576B0093 for ; Thu, 25 Jun 2020 13:16:08 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B6FC5801AD49 for ; Thu, 25 Jun 2020 17:16:07 +0000 (UTC) X-FDA: 76968387174.15.hole64_5a0df2726e4e Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin15.hostedemail.com (Postfix) with ESMTP id 2291718208431 for ; Thu, 25 Jun 2020 17:10:25 +0000 (UTC) X-HE-Tag: hole64_5a0df2726e4e X-Filterd-Recvd-Size: 2956 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf40.hostedemail.com (Postfix) with ESMTP for ; Thu, 25 Jun 2020 17:10:24 +0000 (UTC) Received: from gaia (unknown [2.26.170.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C448520706; Thu, 25 Jun 2020 17:10:21 +0000 (UTC) Date: Thu, 25 Jun 2020 18:10:19 +0100 From: Catalin Marinas To: Matthew Wilcox Cc: Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, Will Deacon , Dave P Martin , Vincenzo Frascino , Szabolcs Nagy , Kevin Brodsky , Andrey Konovalov , Peter Collingbourne , Steven Price Subject: Re: [PATCH v5 06/25] mm: Add PG_ARCH_2 page flag Message-ID: <20200625170954.GD14812@gaia> References: <20200624175244.25837-1-catalin.marinas@arm.com> <20200624175244.25837-7-catalin.marinas@arm.com> <20200624113307.6165b3db2404c9d37b870a90@linux-foundation.org> <20200624183647.GU21350@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200624183647.GU21350@casper.infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: 2291718208431 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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: On Wed, Jun 24, 2020 at 07:36:47PM +0100, Matthew Wilcox wrote: > On Wed, Jun 24, 2020 at 11:33:07AM -0700, Andrew Morton wrote: > > On Wed, 24 Jun 2020 18:52:25 +0100 Catalin Marinas wrote: > > > From: Steven Price > > > > > > For arm64 MTE support it is necessary to be able to mark pages that > > > contain user space visible tags that will need to be saved/restored e.g. > > > when swapped out. > > > > > > To support this add a new arch specific flag (PG_ARCH_2) that arch code > > > can opt into using ARCH_USES_PG_ARCH_2. > > > > > > ... > > > > > > --- a/fs/proc/page.c > > > +++ b/fs/proc/page.c > > > @@ -217,6 +217,9 @@ u64 stable_page_flags(struct page *page) > > > u |= kpf_copy_bit(k, KPF_PRIVATE_2, PG_private_2); > > > u |= kpf_copy_bit(k, KPF_OWNER_PRIVATE, PG_owner_priv_1); > > > u |= kpf_copy_bit(k, KPF_ARCH, PG_arch_1); > > > +#ifdef CONFIG_ARCH_USES_PG_ARCH_2 > > > + u |= kpf_copy_bit(k, KPF_ARCH_2, PG_arch_2); > > > +#endif > > > > Do we need CONFIG_ARCH_USES_PG_ARCH_2? What would be the downside to > > giving every architecture a PG_arch_2, but only arm64 uses it (at > > present)? > > 32-bit architectures don't have space for it. We could condition it on > CONFIG_64BIT instead. I'll this, though we'd still need some #ifdefs (OTOH, we get rid of the Kconfig entry). -- Catalin