From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758170AbdJQJn2 (ORCPT ); Tue, 17 Oct 2017 05:43:28 -0400 Received: from mail-lf0-f52.google.com ([209.85.215.52]:45220 "EHLO mail-lf0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758076AbdJQJnY (ORCPT ); Tue, 17 Oct 2017 05:43:24 -0400 X-Google-Smtp-Source: ABhQp+SJi9hyrvBqBud3UVViahSjy9N0KqzZBLZR3neodLfTcTICr2WkIsYL/3xR/IKoEmVZTrP9xA== Subject: Re: [PATCH V8 5/5] libata: Align DMA buffer to dma_get_cache_alignment() To: Huacai Chen , Christoph Hellwig Cc: Marek Szyprowski , Robin Murphy , Andrew Morton , Fuxin Zhang , linux-kernel@vger.kernel.org, Ralf Baechle , James Hogan , linux-mips@linux-mips.org, "James E . J . Bottomley" , "Martin K . Petersen" , linux-scsi@vger.kernel.org, Tejun Heo , linux-ide@vger.kernel.org, stable@vger.kernel.org References: <1508227542-13165-1-git-send-email-chenhc@lemote.com> <1508227542-13165-5-git-send-email-chenhc@lemote.com> From: Sergei Shtylyov Message-ID: <94f55c1e-7553-0fc8-124e-ac6df5ac10ce@cogentembedded.com> Date: Tue, 17 Oct 2017 12:43:22 +0300 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1508227542-13165-5-git-send-email-chenhc@lemote.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/17/2017 11:05 AM, Huacai Chen wrote: > In non-coherent DMA mode, kernel uses cache flushing operations to > maintain I/O coherency, so in ata_do_dev_read_id() the DMA buffer > should be aligned to ARCH_DMA_MINALIGN. Otherwise, If a DMA buffer > and a kernel structure share a same cache line, and if the kernel > structure has dirty data, cache_invalidate (no writeback) will cause > data corruption. > > Cc: stable@vger.kernel.org > Signed-off-by: Huacai Chen > --- > drivers/ata/libata-core.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c > index ee4c1ec..e134955 100644 > --- a/drivers/ata/libata-core.c > +++ b/drivers/ata/libata-core.c > @@ -1833,8 +1833,19 @@ static u32 ata_pio_mask_no_iordy(const struct ata_device *adev) > unsigned int ata_do_dev_read_id(struct ata_device *dev, > struct ata_taskfile *tf, u16 *id) > { > - return ata_exec_internal(dev, tf, NULL, DMA_FROM_DEVICE, > - id, sizeof(id[0]) * ATA_ID_WORDS, 0); > + u16 *devid; > + int res, size = sizeof(u16) * ATA_ID_WORDS; > + > + if (IS_ALIGNED((unsigned long)id, dma_get_cache_alignment(&dev->tdev))) > + res = ata_exec_internal(dev, tf, NULL, DMA_FROM_DEVICE, id, size, 0); > + else { > + devid = kmalloc(size, GFP_KERNEL); > + res = ata_exec_internal(dev, tf, NULL, DMA_FROM_DEVICE, devid, size, 0); > + memcpy(id, devid, size); > + kfree(devid); > + } > + > + return res; This function is called only for the PIO mode commands, so I doubt this is necessary... MBR, Sergei