Re: [PATCH v2 09/11] dmaengine: ioat: disable relaxed ordering before registering the device

[Dave Jiang]

On 7/21/26 8:57 AM, Logan Gunthorpe wrote:
> ioat3_dma_probe() disabled PCIe relaxed ordering after calling
> dma_async_device_register(), so if an error occurs and the code jumps
> to err_disable_interrupts, the function returns with the device still
> registered in the core's dma_device_list while the caller frees the
> ioatdma_device struct, leaving a dangling registration that anything
> walking the device list can dereference after it's been freed.
> 
> Move the capability read/write ahead of dma_async_device_register()
> instead. Nothing after registration depends on relaxed ordering
> already being disabled, and nothing before it depends on the device
> being registered, so this is a plain reordering. It also means every
> remaining step after registration can't fail, so there's no need to
> ever have to unregister the device once registered.
> 
> Fixes: 511deae0261c ("dmaengine: ioatdma: disable relaxed ordering for ioatdma")
> Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
> Link: https://lore.kernel.org/dmaengine/20260707165906.249F41F000E9@xxxxxxxxxxxxxxx
> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>

Acked-by: Dave Jiang <dave.jiang@xxxxxxxxx>

> ---
>  drivers/dma/ioat/init.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/dma/ioat/init.c b/drivers/dma/ioat/init.c
> index 737496391109..a57024c4b066 100644
> --- a/drivers/dma/ioat/init.c
> +++ b/drivers/dma/ioat/init.c
> @@ -1170,15 +1170,6 @@ static int ioat3_dma_probe(struct ioatdma_device *ioat_dma, int dca)
>  		       ioat_chan->reg_base + IOAT_DCACTRL_OFFSET);
>  	}
>  
> -	err = dma_async_device_register(&ioat_dma->dma_dev);
> -	if (err)
> -		goto err_disable_interrupts;
> -
> -	ioat_kobject_add(ioat_dma, &ioat_ktype);
> -
> -	if (dca)
> -		ioat_dma->dca = ioat_dca_init(pdev, ioat_dma->reg_base);
> -
>  	/* disable relaxed ordering */
>  	err = pcie_capability_read_word(pdev, PCI_EXP_DEVCTL, &val16);
>  	if (err) {
> @@ -1194,6 +1185,15 @@ static int ioat3_dma_probe(struct ioatdma_device *ioat_dma, int dca)
>  		goto err_disable_interrupts;
>  	}
>  
> +	err = dma_async_device_register(&ioat_dma->dma_dev);
> +	if (err)
> +		goto err_disable_interrupts;
> +
> +	ioat_kobject_add(ioat_dma, &ioat_ktype);
> +
> +	if (dca)
> +		ioat_dma->dca = ioat_dca_init(pdev, ioat_dma->reg_base);
> +
>  	if (ioat_dma->cap & IOAT_CAP_DPS)
>  		writeb(ioat_pending_level + 1,
>  		       ioat_dma->reg_base + IOAT_PREFETCH_LIMIT_OFFSET);