Re: [PATCH v19 02/14] cxl/ras: Fix cxl_rch_get_aer_severity() wrong severity register

[Lukas Wunner <lukas@wunner.de>]

On Mon, Aug 03, 2026 at 05:17:58PM -0500, Terry Bowman wrote:
> +++ b/drivers/cxl/core/ras_rch.c
> @@ -94,11 +94,11 @@ static bool cxl_rch_get_aer_info(void __iomem *aer_base,
>  static bool cxl_rch_get_aer_severity(struct aer_capability_regs *aer_regs,
>  				     int *severity)
>  {
> -	if (aer_regs->uncor_status & ~aer_regs->uncor_mask) {
> -		if (aer_regs->uncor_status & PCI_ERR_ROOT_FATAL_RCV)
> -			*severity = AER_FATAL;
> -		else
> -			*severity = AER_NONFATAL;
> +	u32 uncor_status = aer_regs->uncor_status & ~aer_regs->uncor_mask;
> +
> +	if (uncor_status) {
> +		*severity = (uncor_status & aer_regs->uncor_severity) ?
> +			     AER_FATAL : AER_NONFATAL;
>  		return true;
>  	}
>  

Independently of this patch, I'm wondering why the severity is inferred
from the AER registers.  I would assume that the severity always equals
the message received by the RCEC (ERR_COR, ERR_NONFATAL or ERR_FATAL).

So the severity could be passed to cxl_handle_rdport_errors() from its
callers:  cxl_cor_err_detected() would pass AER_CORRECTABLE and
cxl_error_detected() would pass ERR_NONFATAL or ERR_FATAL (depending
on the "state" variable).

cxl_handle_rdport_errors() would no longer need to call
cxl_rch_get_aer_severity(), so the latter could be removed.

Am I missing something?  Is a scenario ever conceivable where the RCEC
receives a message with different severity than what is inferred from
the registers by cxl_rch_get_aer_severity()?

And a related question:  linux-next commit 21963e6e4e04 ("PCI/AER:
Support Advisory Non-Fatal Errors") enables support for Non-Fatal
Errors which are signaled with an ERR_COR message.

These so-called Advisory Non-Fatal Errors set one bit in the Correctable
Error Status Register (Advisory Non-Fatal Error Status, bit 13) and
additionally one or more bits in the Uncorrectable Error Status Register
(see the commit for details).

cxl_rch_get_aer_severity() is not able to cope with such errors and
will incorrectly infer that the severity is AER_NONFATAL.

Now I *think* this is not a problem because Advisory Non-Fatal Errors
are masked by default and the commit only unmasks them on regular PCI
devices, not in the RCRB of a CXL device.  Only once bit 13 in the
Correctable Error Mask Register is cleared in the RCRB will
cxl_rch_get_aer_severity() fail.  Right?

Thanks,

Lukas