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 X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B4702C433DB for ; Wed, 17 Mar 2021 11:45:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F01064F64 for ; Wed, 17 Mar 2021 11:45:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231428AbhCQLpB (ORCPT ); Wed, 17 Mar 2021 07:45:01 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:2707 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230442AbhCQLom (ORCPT ); Wed, 17 Mar 2021 07:44:42 -0400 Received: from fraeml705-chm.china.huawei.com (unknown [172.18.147.206]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4F0p9c4xctz680sN; Wed, 17 Mar 2021 19:40:04 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml705-chm.china.huawei.com (10.206.15.54) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2106.2; Wed, 17 Mar 2021 12:44:38 +0100 Received: from [10.47.1.152] (10.47.1.152) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2106.2; Wed, 17 Mar 2021 11:44:37 +0000 Subject: Re: [PATCH] scsi: libsas: Reset num_scatter if libata mark qc as NODATA To: Jolly Shah , , , , , , , CC: , References: <20210316193905.1673600-1-jollys@google.com> From: John Garry Message-ID: <5e2c35b6-a9c4-0637-738b-ff6920635425@huawei.com> Date: Wed, 17 Mar 2021 11:42:29 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <20210316193905.1673600-1-jollys@google.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.1.152] X-ClientProxiedBy: lhreml716-chm.china.huawei.com (10.201.108.67) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/03/2021 19:39, Jolly Shah wrote: > When the cache_type for the scsi device is changed, the scsi layer > issues a MODE_SELECT command. The caching mode details are communicated > via a request buffer associated with the scsi command with data > direction set as DMA_TO_DEVICE (scsi_mode_select). When this command > reaches the libata layer, as a part of generic initial setup, libata > layer sets up the scatterlist for the command using the scsi command > (ata_scsi_qc_new). This command is then translated by the libata layer > into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer > treats this as a non data command (ata_mselect_caching), since it only > needs an ata taskfile to pass the caching on/off information to the > device. It does not need the scatterlist that has been setup, so it does > not perform dma_map_sg on the scatterlist (ata_qc_issue). So if we don't perform the dma_map_sg() on the sgl at this point, then it seems to me that we should not perform for_each_sg() on it either, right? That is still what happens in sas_ata_qc_issue() in this case. > Unfortunately, > when this command reaches the libsas layer(sas_ata_qc_issue), libsas > layer sees it as a non data command with a scatterlist. It cannot > extract the correct dma length, since the scatterlist has not been > mapped with dma_map_sg for a DMA operation. When this partially > constructed SAS task reaches pm80xx LLDD, it results in below warning. > > "pm80xx_chip_sata_req 6058: The sg list address > start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff > end_addr_low=0xffffffff has crossed 4G boundary" > > This patch assigns appropriate value to num_sectors for ata non data > commands. > > Signed-off-by: Jolly Shah > --- > drivers/scsi/libsas/sas_ata.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c > index 024e5a550759..94ec08cebbaa 100644 > --- a/drivers/scsi/libsas/sas_ata.c > +++ b/drivers/scsi/libsas/sas_ata.c > @@ -209,10 +209,12 @@ static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc) > task->num_scatter = si; > } > > - if (qc->tf.protocol == ATA_PROT_NODATA) > + if (qc->tf.protocol == ATA_PROT_NODATA) { > task->data_dir = DMA_NONE; > - else > + task->num_scatter = 0; task->num_scatter has already been set in this function. Best not set it twice. Thanks, John > + } else { > task->data_dir = qc->dma_dir; > + } > task->scatter = qc->sg; > task->ata_task.retry_count = 1; > task->task_state_flags = SAS_TASK_STATE_PENDING; >