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dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 49d3Fb1tkbzDqnk for ; Thu, 4 Jun 2020 21:19:15 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=198.145.29.99; helo=mail.kernel.org; envelope-from=will@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=kernel.org Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=default header.b=q+N79pq8; dkim-atps=neutral Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 49d3CZ6XSbzDqld for ; Thu, 4 Jun 2020 21:17:30 +1000 (AEST) Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (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 EED9C20663; Thu, 4 Jun 2020 11:17:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591269448; bh=TD23lUmHIH4fDCI+FcUMyA2oC82x0Bai1U3IaWCZkEg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=q+N79pq8MdT0YLoIZImKz0WOU1Deu3HxicOZmkxWveX1KC5zJCO5lUjeefXxlaNlA nvlomYyqjE0JUNTYYDsUoKmE5l0f+d/we/lrFkL+eaux0MSAA9zCr0YPF7jbG2a1Yb aMHs/qa37gU+2K/Avj/2JrsRlzZ3m9ESbYbEixdA= Date: Thu, 4 Jun 2020 12:17:23 +0100 From: Will Deacon To: Christophe Leroy Subject: Re: linux-next: build failure on powerpc 8xx with 16k pages Message-ID: <20200604111723.GA1267@willie-the-truck> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Stephen Rothwell , peterz@infradead.org, Linux Kernel Mailing List , Linux Next Mailing List , Andrew Morton , PowerPC , Thomas Gleixner Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi, [+Peter] On Thu, Jun 04, 2020 at 10:48:03AM +0000, Christophe Leroy wrote: > Using mpc885_ads_defconfig with CONFIG_PPC_16K_PAGES instead of > CONFIG_PPC_4K_PAGES, getting the following build failure: > > CC mm/gup.o > In file included from ./include/linux/kernel.h:11:0, > from mm/gup.c:2: > In function 'gup_hugepte.constprop', > inlined from 'gup_huge_pd.isra.78' at mm/gup.c:2465:8: > ./include/linux/compiler.h:392:38: error: call to '__compiletime_assert_257' > declared with attribute error: Unsupported access size for > {READ,WRITE}_ONCE(). > _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > ^ > ./include/linux/compiler.h:373:4: note: in definition of macro > '__compiletime_assert' > prefix ## suffix(); \ > ^ > ./include/linux/compiler.h:392:2: note: in expansion of macro > '_compiletime_assert' > _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > ^ > ./include/linux/compiler.h:405:2: note: in expansion of macro > 'compiletime_assert' > compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ > ^ > ./include/linux/compiler.h:291:2: note: in expansion of macro > 'compiletime_assert_rwonce_type' > compiletime_assert_rwonce_type(x); \ > ^ > mm/gup.c:2428:8: note: in expansion of macro 'READ_ONCE' > pte = READ_ONCE(*ptep); > ^ > In function 'gup_get_pte', > inlined from 'gup_pte_range' at mm/gup.c:2228:9, > inlined from 'gup_pmd_range' at mm/gup.c:2613:15, > inlined from 'gup_pud_range' at mm/gup.c:2641:15, > inlined from 'gup_p4d_range' at mm/gup.c:2666:15, > inlined from 'gup_pgd_range' at mm/gup.c:2694:15, > inlined from 'internal_get_user_pages_fast' at mm/gup.c:2785:3: At first glance, this looks like a real bug in the 16k page code -- you're loading the pte non-atomically on the fast GUP path and so you're prone to tearing, which probably isn't what you want. For a short-term hack, I'd suggest having CONFIG_HAVE_FAST_GUP depend on !CONFIG_PPC_16K_PAGES, but if you want to support this them you'll need to rework your pte_t so that it can be loaded atomically. Will