Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <bccbcc9b-4750-a1a7-130f-69eeea5dcb23@acm.org>
Date:   Wed, 8 Jun 2022 14:07:05 -0700
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.8.0
Subject: Re: [PATCH v3 3/4] scsi: core: Cap shost max_sectors according to DMA
 optimum mapping limits
Content-Language: en-US
To:     John Garry <john.garry@huawei.com>,
        damien.lemoal@opensource.wdc.com, joro@8bytes.org, will@kernel.org,
        jejb@linux.ibm.com, martin.petersen@oracle.com, hch@lst.de,
        m.szyprowski@samsung.com, robin.murphy@arm.com
Cc:     linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-ide@vger.kernel.org, iommu@lists.linux-foundation.org,
        linux-scsi@vger.kernel.org, liyihang6@hisilicon.com,
        chenxiang66@hisilicon.com, thunder.leizhen@huawei.com
References: <1654507822-168026-1-git-send-email-john.garry@huawei.com>
 <1654507822-168026-4-git-send-email-john.garry@huawei.com>
 <fe365aa8-00d5-153d-ceb2-f887a71a6927@acm.org>
 <31417477-953d-283e-808e-cf8701e820a8@huawei.com>
From:   Bart Van Assche <bvanassche@acm.org>
In-Reply-To: <31417477-953d-283e-808e-cf8701e820a8@huawei.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 6/8/22 10:50, John Garry wrote:
> Please note that this limit only applies if we have an IOMMU enabled for 
> the scsi host dma device. Otherwise we are limited by dma direct or 
> swiotlb max mapping size, as before.

SCSI host bus adapters that support 64-bit DMA may support much larger 
transfer sizes than 128 KiB.

Thanks,

Bart.