Re: [PATCH] cxl/port: Fix endpoint RAS error unmasking

[Dave Jiang]

On 10/30/26 2:59 AM, Richard Cheng wrote:
> Commit dab7162d0ae7 ("cxl/port: Move endpoint component register
> management to cxl_port") moved EP RAS handling from cxl_pci to cxl_port,
> while cxl_ras_unmask() have the assumption that port->uport_dev is a PCI

s/have/has/

> device.
> If the topology use cxl_memdev as uport_dev, the PCI check will fail and
> CXL RAS masks remain set.

Endpoint ports always use memdev as uport_dev right? Maybe we can say the unmask has never run.

> 
> Resolve memdev uports to their parent dev and verify the device is PCI.
> 
> Fixes: dab7162d0ae7 ("cxl/port: Move endpoint component register management to cxl_port")
> Signed-off-by: Richard Cheng <icheng@xxxxxxxxxx>
> ---
> Reproducer is a QEMU Type-3 guest
> 
> 1. Ensure no CXL region is active and PCIe AER is enabled.
> 2. Restore the emulated RAS registers to their reset masks.
> 3. Reprobe cxl_pci and read the masks again.
> 
> ```
> BDF=$(basename "$(dirname "$(readlink -f /sys/bus/cxl/devices/mem0)")")
> BAR0=$(awk 'NR == 1 { print $1 }' /sys/bus/pci/devices/$BDF/resource)
> UNC_MASK=$(printf '0x%x' $((BAR0 + 0x1084)))
> COR_MASK=$(printf '0x%x' $((BAR0 + 0x1090)))
> 
> busybox devmem "$UNC_MASK" 32 0x1cfff
> busybox devmem "$COR_MASK" 32 0x7f
> 
> echo "$BDF" > /sys/bus/pci/drivers/cxl_pci/unbind
> echo "$BDF" > /sys/bus/pci/drivers/cxl_pci/bind
> udevadm settle
> 
> busybox devmem "$UNC_MASK" 32
> busybox devmem "$COR_MASK" 32
> ```
> 
> Before the fix, the masks remain 0x1cfff and 0x7f. After the fix,
> both masks read as zero.
> 
> Best regards,
> Richard Cheng.
> ---
>  drivers/cxl/port.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
> index c12fd0b89883..c48216e5078f 100644
> --- a/drivers/cxl/port.c
> +++ b/drivers/cxl/port.c
> @@ -74,15 +74,18 @@ static int cxl_switch_port_probe(struct cxl_port *port)
>  
>  static int cxl_ras_unmask(struct cxl_port *port)
>  {
> +	struct device *host = port->uport_dev;
>  	struct pci_dev *pdev;
>  	void __iomem *addr;
>  	u32 orig_val, val, mask;
>  	u16 cap;
>  	int rc;
>  
> -	if (!dev_is_pci(port->uport_dev))
> +	if (is_cxl_memdev(host))
> +		host = host->parent;
> +	if (!host || !dev_is_pci(host))
>  		return 0;
> -	pdev = to_pci_dev(port->uport_dev);
> +	pdev = to_pci_dev(host);

Can we simplify this to something like:
	struct cxl_memdev *cxlmd = to_cxl_memdev(port->uport_dev);
	struct device *parent = cxlmd->dev.parent;

	if (!dev_is_pci(parent))
		return 0;
	pdev = to_pci_dev(parent));

Also, maybe we should rename it to cxl_endpoint_ras_unmask(struct cxl_port *endpoint) to be intentionally clear?

>  
>  	if (!port->regs.ras) {
>  		pci_dbg(pdev, "No RAS registers.\n");
> 
> base-commit: d135ab453a7400a34930bdda1ef4bdc8acfac80e