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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6A342CCA487 for ; Thu, 23 Jun 2022 18:23:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237536AbiFWSWu (ORCPT ); Thu, 23 Jun 2022 14:22:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56792 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237054AbiFWSUg (ORCPT ); Thu, 23 Jun 2022 14:20:36 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3E5CC680A3; Thu, 23 Jun 2022 10:25:09 -0700 (PDT) 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 dfw.source.kernel.org (Postfix) with ESMTPS id A793560B79; Thu, 23 Jun 2022 17:25:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 809B9C3411B; Thu, 23 Jun 2022 17:25:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1656005108; bh=SRMKkR6B/s1amXppPbKxKENrJIwF9K0pCjkqpT0XZf0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HkuAvrA54Gg29IxW9p3Pxl0sIJM6XvZRExn53K8v9CbsIEIs00k5dk+YAZafVDUcz AUyyN5Mi+M88XdXyjuAQ2X1tNEVthHg3Oe1hjWJPPZRUV7b8zpxNyxVAGq6XOu1SW2 hIJpWkMfQ+klnXuzs3Bi46bkkK8+KPDEJult+49M= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ard Biesheuvel , Christoph Hellwig , Robin Murphy , Russell King , Will Deacon , Catalin Marinas Subject: [PATCH 5.4 10/11] arm64: mm: Dont invalidate FROM_DEVICE buffers at start of DMA transfer Date: Thu, 23 Jun 2022 18:45:14 +0200 Message-Id: <20220623164321.498480839@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220623164321.195163701@linuxfoundation.org> References: <20220623164321.195163701@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Will Deacon commit c50f11c6196f45c92ca48b16a5071615d4ae0572 upstream. Invalidating the buffer memory in arch_sync_dma_for_device() for FROM_DEVICE transfers When using the streaming DMA API to map a buffer prior to inbound non-coherent DMA (i.e. DMA_FROM_DEVICE), we invalidate any dirty CPU cachelines so that they will not be written back during the transfer and corrupt the buffer contents written by the DMA. This, however, poses two potential problems: (1) If the DMA transfer does not write to every byte in the buffer, then the unwritten bytes will contain stale data once the transfer has completed. (2) If the buffer has a virtual alias in userspace, then stale data may be visible via this alias during the period between performing the cache invalidation and the DMA writes landing in memory. Address both of these issues by cleaning (aka writing-back) the dirty lines in arch_sync_dma_for_device(DMA_FROM_DEVICE) instead of discarding them using invalidation. Cc: Ard Biesheuvel Cc: Christoph Hellwig Cc: Robin Murphy Cc: Russell King Cc: Link: https://lore.kernel.org/r/20220606152150.GA31568@willie-the-truck Signed-off-by: Will Deacon Reviewed-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20220610151228.4562-2-will@kernel.org Signed-off-by: Catalin Marinas Signed-off-by: Greg Kroah-Hartman --- arch/arm64/mm/cache.S | 2 -- 1 file changed, 2 deletions(-) --- a/arch/arm64/mm/cache.S +++ b/arch/arm64/mm/cache.S @@ -228,8 +228,6 @@ ENDPIPROC(__dma_flush_area) * - dir - DMA direction */ ENTRY(__dma_map_area) - cmp w2, #DMA_FROM_DEVICE - b.eq __dma_inv_area b __dma_clean_area ENDPIPROC(__dma_map_area)