linux-kernel - Re: [PATCH 7/8] mpt3sas: set an unlimited max_segment

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Date:   Tue, 18 Jun 2019 08:46:40 +0800
From:   Ming Lei <tom.leiming@...il.com>
To:     Christoph Hellwig <hch@....de>
Cc:     "Martin K . Petersen" <martin.petersen@...cle.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Max Gurtovoy <maxg@...lanox.com>,
        Bart Van Assche <bvanassche@....org>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Linux SCSI List <linux-scsi@...r.kernel.org>,
        megaraidlinux.pdl@...adcom.com, MPT-FusionLinux.pdl@...adcom.com,
        linux-hyperv@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/8] mpt3sas: set an unlimited max_segment_size for SAS
 3.0 HBAs

On Mon, Jun 17, 2019 at 8:21 PM Christoph Hellwig <hch@....de> wrote:
>
> When using a virt_boundary_mask, as done for NVMe devices attached to
> mpt3sas controllers we require an unlimited max_segment_size, as the
> virt boundary merging code assumes that.  But we also need to propagate
> that to the DMA mapping layer to make dma-debug happy.  The SCSI layer
> takes care of that when using the per-host virt_boundary setting, but
> given that mpt3sas only wants to set the virt_boundary for actual
> NVMe devices we can't rely on that.  The DMA layer maximum segment
> is global to the HBA however, so we have to set it explicitly.  This
> patch assumes that mpt3sas does not have a segment size limitation,
> which seems true based on the SGL format, but will need to be verified.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  drivers/scsi/mpt3sas/mpt3sas_scsih.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> index 1ccfbc7eebe0..c719b807f6d8 100644
> --- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> +++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> @@ -10222,6 +10222,7 @@ static struct scsi_host_template mpt3sas_driver_template = {
>         .this_id                        = -1,
>         .sg_tablesize                   = MPT3SAS_SG_DEPTH,
>         .max_sectors                    = 32767,
> +       .max_segment_size               = 0xffffffff,

.max_segment_size should be aligned, either setting it here correctly or
forcing to make it aligned in scsi-core.

Thanks,
Ming Lei