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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8CECEC7619A for ; Mon, 27 Mar 2023 12:21:11 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4PlX3V1TkMz3fmL for ; Mon, 27 Mar 2023 23:21:10 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=CPGniWUc; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=145.40.68.75; helo=ams.source.kernel.org; envelope-from=arnd@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=CPGniWUc; dkim-atps=neutral Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) (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 4PlWwQ31GXz3fT3 for ; Mon, 27 Mar 2023 23:15:02 +1100 (AEDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C83ABB81158; Mon, 27 Mar 2023 12:14:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 660FDC4331E; Mon, 27 Mar 2023 12:14:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1679919298; bh=Y+wx0FiQgLjkqhPKxtczgrowoCTrPuzhrrVdIO/KSAA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CPGniWUcV5VUAZiOWzIY5/EsUqYQgyEzxjQ8UMeF3Al20/Hh61j9pc8T9PS2mzH4N RSYd/J7YHPH5Nmfk7XsUSK79nWPo+dGlRYvhxWqnqg+N+CIjbuT/Wb2iRTjyp1l0YE q3AT+X8nNFF6xSpGl06sKKOZy0e/LCKNsDpUgC07vuwopI9ykgcvXa2bBFGYOjVaGl X5PV9Eydwk0GTrNzStCQUtT6ovd3xxwDRfs6NRHuZY4OjKijI2Z6KdM95ztBnGcDwK 5HPw8DEJ4VDkMTWgdZ8nt+6QlnfKBn6oiVjPRF9H4yYTieJdfpVbSHx8IkThq5gzbA lsa0aYW1Hchqw== From: Arnd Bergmann To: linux-kernel@vger.kernel.org Subject: [PATCH 07/21] powerpc: dma-mapping: always clean cache in _for_device() op Date: Mon, 27 Mar 2023 14:13:03 +0200 Message-Id: <20230327121317.4081816-8-arnd@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230327121317.4081816-1-arnd@kernel.org> References: <20230327121317.4081816-1-arnd@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: Rich Felker , linux-sh@vger.kernel.org, Catalin Marinas , Linus Walleij , John Paul Adrian Glaubitz , Max Filippov , Conor Dooley , Guo Ren , linux-csky@vger.kernel.org, sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Will Deacon , Christoph Hellwig , Helge Deller , Russell King , Geert Uytterhoeven , Vineet Gupta , linux-snps-arc@lists.infradead.org, linux-xtensa@linux-xtensa.org, Arnd Bergmann , Brian Cain , Lad Prabhakar , linux-m68k@lists.linux-m68k.org, Paul Walmsley , Stafford Horne , linux-arm-kernel@lists.infradead.org, Neil Armstrong , Michal Sime k , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, linux-openrisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mips@vger.kernel.org, Dinh Nguyen , Palmer Dabbelt , linux-hexagon@vger.kernel.org, linux-oxnas@groups.io, Robin Murphy , "David S. Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Arnd Bergmann The powerpc implementation of arch_sync_dma_for_device() is unique in that it sometimes performs a full flush for the arch_sync_dma_for_device(paddr, size, DMA_FROM_DEVICE) operation when the address is unaligned, but otherwise invalidates the caches. Since the _for_cpu() counterpart has to invalidate the cache already in order to avoid stale data from prefetching, this operation only really needs to ensure that there are no dirty cache lines, which can be done using either invalidation or cleaning the cache, but not necessarily both. Most architectures traditionally go for invalidation here, but as Will Deacon points out, this can leak old data to user space if a DMA is started but the device ends up not actually filling the entire buffer, see the link below. The same argument applies to DMA_BIDIRECTIONAL transfers. Using a cache-clean operation is the safe choice here, followed by invalidating the cache after the DMA to get rid of stale data that was prefetched before the completion of the DMA. Link: https://lore.kernel.org/all/20220606152150.GA31568@willie-the-truck/ Signed-off-by: Arnd Bergmann --- arch/powerpc/mm/dma-noncoherent.c | 21 +-------------------- 1 file changed, 1 insertion(+), 20 deletions(-) diff --git a/arch/powerpc/mm/dma-noncoherent.c b/arch/powerpc/mm/dma-noncoherent.c index e108cacf877f..00e59a4faa2b 100644 --- a/arch/powerpc/mm/dma-noncoherent.c +++ b/arch/powerpc/mm/dma-noncoherent.c @@ -104,26 +104,7 @@ static void __dma_phys_op(phys_addr_t paddr, size_t size, enum dma_cache_op op) void arch_sync_dma_for_device(phys_addr_t paddr, size_t size, enum dma_data_direction dir) { - switch (direction) { - case DMA_NONE: - BUG(); - case DMA_FROM_DEVICE: - /* - * invalidate only when cache-line aligned otherwise there is - * the potential for discarding uncommitted data from the cache - */ - if ((start | end) & (L1_CACHE_BYTES - 1)) - __dma_phys_op(start, end, DMA_CACHE_FLUSH); - else - __dma_phys_op(start, end, DMA_CACHE_INVAL); - break; - case DMA_TO_DEVICE: /* writeback only */ - __dma_phys_op(start, end, DMA_CACHE_CLEAN); - break; - case DMA_BIDIRECTIONAL: /* writeback and invalidate */ - __dma_phys_op(start, end, DMA_CACHE_FLUSH); - break; - } + __dma_phys_op(start, end, DMA_CACHE_CLEAN); } void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size, -- 2.39.2