Re: [PATCH v4] mpt3sas: Limit NVMe request size to 2 MiB

[Mira Limbeck <m.limbeck@proxmox.com>]

On 4/14/26 1:13 PM, Ranjan Kumar wrote:
> The HBA firmware reports NVMe MDTS values based on the underlying drive
> capability. However, because the driver allocates a fixed 4K buffer for
> the PRP list, accommodating at most 512 entries, the driver supports a
> maximum I/O transfer size of 2 MiB.
> 
> Limit max_hw_sectors to the smaller of the reported MDTS and the
> 2 MiB driver limit to prevent issuing oversized I/O that may lead
> to a kernel oops.
> 
> Cc: stable@vger.kernel.org
> Fixes: 9b8b84879d4a ("block: Increase BLK_DEF_MAX_SECTORS_CAP")
> Reported-by: Mira Limbeck <m.limbeck@proxmox.com>
> Closes: https://lore.kernel.org/r/291f78bf-4b4a-40dd-867d-053b36c564b3@proxmox.com
> Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9b8b84879d4a
> Suggested-by: Keith Busch <kbusch@kernel.org>
> Signed-off-by: Ranjan Kumar <ranjan.kumar@broadcom.com>
> ---
>  drivers/scsi/mpt3sas/mpt3sas_scsih.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> index 6ff788557294..12caffeed3a0 100644
> --- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> +++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> @@ -2738,8 +2738,20 @@ scsih_sdev_configure(struct scsi_device *sdev, struct queue_limits *lim)
>  				pcie_device->enclosure_level,
>  				pcie_device->connector_name);
>  
> +		/*
> +		 * The HBA firmware passes the NVMe drive's MDTS
> +		 * (Maximum Data Transfer Size) up to the driver. However,
> +		 * the driver hardcodes a 4K buffer size for the PRP list,
> +		 * accommodating at most 512 entries. This strictly limits
> +		 * the maximum supported NVMe I/O transfer to 2 MiB.
> +		 *
> +		 * Cap max_hw_sectors to the smaller of the drive's reported
> +		 * MDTS or the 2 MiB driver limit to prevent kernel oopses.
> +		 */
> +		lim->max_hw_sectors = SZ_2M >> SECTOR_SHIFT;
>  		if (pcie_device->nvme_mdts)
> -			lim->max_hw_sectors = pcie_device->nvme_mdts / 512;
> +			lim->max_hw_sectors = min(lim->max_hw_sectors,
> +					pcie_device->nvme_mdts >> SECTOR_SHIFT);
>  
>  		pcie_device_put(pcie_device);
>  		spin_unlock_irqrestore(&ioc->pcie_device_lock, flags);

Thank you for providing this patch.

We tested it on our test machine on top of 7.0-rc7.
Without the patch, we saw the same call traces as before. With this patch applied no such call traces were logged.
So looks like it fixes the issue in our case.

I can't say much to the patch itself, but I can provide a tested-by.

Tested-by: Mira Limbeck <m.limbeck@proxmox.com>