linux-kernel - Re: [PATCH v3 1/3] cxl/pci: Fix appropriate checking for

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Message-ID: <20230804130929.00007dfb@Huawei.com>
Date:   Fri, 4 Aug 2023 13:09:29 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-cxl@...r.kernel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
        <oohall@...il.com>, Lukas Wunner <lukas@...ner.de>,
        "Kuppuswamy Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Mahesh J Salgaonkar" <mahesh@...ux.ibm.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        "Ira Weiny" <ira.weiny@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        "Dan Williams" <dan.j.williams@...el.com>,
        Yazen Ghannam <yazen.ghannam@....com>,
        Terry Bowman <terry.bowman@....com>,
        Robert Richter <rrichter@....com>
Subject: Re: [PATCH v3 1/3] cxl/pci: Fix appropriate checking for _OSC while
 handling CXL RAS registers

On Thu, 3 Aug 2023 23:01:27 +0000
Smita Koralahalli <Smita.KoralahalliChannabasappa@....com> wrote:

> According to Section 9.17.2, Table 9-26 of CXL Specification [1], owner
> of AER should also own CXL Protocol Error Management as there is no
> explicit control of CXL Protocol error. And the CXL RAS Cap registers
> reported on Protocol errors should check for AER _OSC rather than CXL
> Memory Error Reporting Control _OSC.
> 
> The CXL Memory Error Reporting Control _OSC specifically highlights
> handling Memory Error Logging and Signaling Enhancements. These kinds of
> errors are reported through a device's mailbox and can be managed
> independently from CXL Protocol Errors.
> 
> This change fixes handling and reporting CXL Protocol Errors and RAS
> registers natively with native AER and FW-First CXL Memory Error Reporting
> Control.
> 
> [1] Compute Express Link (CXL) Specification, Revision 3.1, Aug 1 2022.
> 
> Fixes: 248529edc86f ("cxl: add RAS status unmasking for CXL")
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
> Reviewed-by: Robert Richter <rrichter@....com>

I'd be tempted to add a comment on why this returns 0 rather than an
error.  I think that makes sense but it isn't immediately obvious from
the local context.

Otherwise LGTM

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>


> ---
> v2:
> 	Added fixes tag.
> 	Included what the patch fixes in commit message.
> v3:
> 	Added "Reviewed-by" tag.
> ---
>  drivers/cxl/pci.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index 1cb1494c28fe..2323169b6e5f 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -541,9 +541,9 @@ static int cxl_pci_ras_unmask(struct pci_dev *pdev)
>  		return 0;
>  	}
>  
> -	/* BIOS has CXL error control */
> -	if (!host_bridge->native_cxl_error)
> -		return -ENXIO;
> +	/* BIOS has PCIe AER error control */
> +	if (!host_bridge->native_aer)
> +		return 0;
>  
>  	rc = pcie_capability_read_word(pdev, PCI_EXP_DEVCTL, &cap);
>  	if (rc)