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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85834C433EF for ; Wed, 29 Sep 2021 10:42:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0B8AA613D3 for ; Wed, 29 Sep 2021 10:42:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0B8AA613D3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 871E36B0098; Wed, 29 Sep 2021 06:42:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 821F994001D; Wed, 29 Sep 2021 06:42:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 711696B009A; Wed, 29 Sep 2021 06:42:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0121.hostedemail.com [216.40.44.121]) by kanga.kvack.org (Postfix) with ESMTP id 65A7D6B0098 for ; Wed, 29 Sep 2021 06:42:48 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 18DCA30C76 for ; Wed, 29 Sep 2021 10:42:48 +0000 (UTC) X-FDA: 78640272816.11.7394404 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf01.hostedemail.com (Postfix) with ESMTP id C3E4550679AD for ; Wed, 29 Sep 2021 10:42:47 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 815A4613D1; Wed, 29 Sep 2021 10:42:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1632912166; bh=nGDQTfZDv9CExyFJB0RbsDORgscyoxeg39JI2IBhJwo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Bfqdw00CNoSOGG5ZjlW9e8wvAbgKJOOqw1oxJbvmzsY+Pm12ZHpB/GpgjhkFFdzli 5icVN9aBABzGOAtkdpr7keKO5Wl3ZZvGKGVKtLcVYYbead4OO2emVRCBhHj0gW4DGB Qj71oW+JlwZdOrEP3OmLEmrdhRru4efXBTVyitAz2gUFWvF18VS2LzxPcatySh6Jg8 ntnmDWE2wtVy1gqRdsiPABenYfNGJdc14369dQlhh1P4Rqz26gbSq3kl0GSQDaY4bS 7FkmBQedVJYCHBfAWxfDKI3X8Davt2iKTi1lRGrlKNlYoOgAUDbAdwOId0N6NZtWrT i1Obz7xf72kVA== Date: Wed, 29 Sep 2021 11:42:42 +0100 From: Will Deacon To: David Hildenbrand Cc: Chris Goldsworthy , Catalin Marinas , Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sudarshan Rajagopalan Subject: Re: [RFC] arm64: mm: update max_pfn after memory hotplug Message-ID: <20210929104241.GA21395@willie-the-truck> References: <595d09279824faf1f54961cef52b745609b05d97.1632437225.git.quic_cgoldswo@quicinc.com> <20210929101028.GB21057@willie-the-truck> <13f56b37-afc7-bf6f-d544-8d6433588bf9@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <13f56b37-afc7-bf6f-d544-8d6433588bf9@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: C3E4550679AD X-Stat-Signature: ha6ghnxhzxb1bkccjt1x6b77ogaozbei Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Bfqdw00C; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf01.hostedemail.com: domain of will@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=will@kernel.org X-HE-Tag: 1632912167-307537 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, Sep 29, 2021 at 12:29:32PM +0200, David Hildenbrand wrote: > On 29.09.21 12:10, Will Deacon wrote: > > On Thu, Sep 23, 2021 at 03:54:48PM -0700, Chris Goldsworthy wrote: > > > From: Sudarshan Rajagopalan > > > > > > After new memory blocks have been hotplugged, max_pfn and max_low_pfn > > > needs updating to reflect on new PFNs being hot added to system. > > > > > > Signed-off-by: Sudarshan Rajagopalan > > > Signed-off-by: Chris Goldsworthy > > > --- > > > arch/arm64/mm/mmu.c | 5 +++++ > > > 1 file changed, 5 insertions(+) > > > > > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > > > index cfd9deb..fd85b51 100644 > > > --- a/arch/arm64/mm/mmu.c > > > +++ b/arch/arm64/mm/mmu.c > > > @@ -1499,6 +1499,11 @@ int arch_add_memory(int nid, u64 start, u64 size, > > > if (ret) > > > __remove_pgd_mapping(swapper_pg_dir, > > > __phys_to_virt(start), size); > > > + else { > > > + max_pfn = PFN_UP(start + size); > > > + max_low_pfn = max_pfn; > > > + } > > > > We use 'max_pfn' as part of the argument to set_max_mapnr(). Does that need > > updating as well? > > > > Do we have sufficient locking to ensure nobody is looking at max_pfn or > > max_low_pfn while we update them? > > Only the write side is protected by memory hotplug locking. The read side is > lockless -- just like all of the other pfn_to_online_page() machinery. Hmm. So the readers can see one of the variables updated but the other one stale? Will