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Received: from mail.kernel.org ([198.145.29.99]) by casper.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1joVON-00011f-Dz for linux-arm-kernel@lists.infradead.org; Thu, 25 Jun 2020 17:10:30 +0000 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 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-Disposition: inline In-Reply-To: <20200624183647.GU21350@casper.infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200625_181027_740657_27303094 X-CRM114-Status: GOOD ( 20.15 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Szabolcs Nagy , Andrey Konovalov , Kevin Brodsky , Steven Price , Peter Collingbourne , linux-mm@kvack.org, Andrew Morton , Vincenzo Frascino , Will Deacon , Dave P Martin , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel