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 CCDC4C433EF for ; Thu, 23 Jun 2022 16:17:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231948AbiFWQRx (ORCPT ); Thu, 23 Jun 2022 12:17:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51322 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232069AbiFWQRt (ORCPT ); Thu, 23 Jun 2022 12:17:49 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 35AEE457B5 for ; Thu, 23 Jun 2022 09:17:48 -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 ams.source.kernel.org (Postfix) with ESMTPS id CBC1DB82474 for ; Thu, 23 Jun 2022 16:17:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D890C3411B; Thu, 23 Jun 2022 16:17:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1656001065; bh=w9vssxCnAThHd+BSfh0MhxhvWTeLf0gzQ97pqxEjOn0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BlJiREW2V3hHeWtzrlNMeDp/oWNKohPJ+M83xsi5FtaoK3glAnJ53kv4DhFhCF7v1 DGaT2LqVWn+VOQCv9I06UcdV09IhwDmqfu+95UVMxXevk7Mne/xFXpgTNL1NjjRpVj p3HS7CZesPauJ6HzZWzUkZ9wZBLk4yfBbgbAMb18= Date: Thu, 23 Jun 2022 18:17:40 +0200 From: Greg Kroah-Hartman To: Catalin Marinas Cc: stable@vger.kernel.org, Will Deacon Subject: Re: [PATCH stable-5.15] arm64: mm: Don't invalidate FROM_DEVICE buffers at start of DMA transfer Message-ID: References: <20220623154412.1117070-1-catalin.marinas@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220623154412.1117070-1-catalin.marinas@arm.com> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, Jun 23, 2022 at 04:44:12PM +0100, Catalin Marinas wrote: > 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 > --- > arch/arm64/mm/cache.S | 2 -- > 1 file changed, 2 deletions(-) All now queued up, thanks. greg k-h