linux-kernel - Re: [PATCH v2 05/14] PCI/AER: Add CXL PCIe port correctable error support in AER service driver

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Message-ID: <20241030151308.000005d5@Huawei.com>
Date: Wed, 30 Oct 2024 15:13:08 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Terry Bowman <terry.bowman@....com>
CC: <ming4.li@...el.com>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
	<dave@...olabs.net>, <dave.jiang@...el.com>, <alison.schofield@...el.com>,
	<vishal.l.verma@...el.com>, <dan.j.williams@...el.com>,
	<bhelgaas@...gle.com>, <mahesh@...ux.ibm.com>, <ira.weiny@...el.com>,
	<oohall@...il.com>, <Benjamin.Cheatham@....com>, <rrichter@....com>,
	<nathan.fontenot@....com>, <Smita.KoralahalliChannabasappa@....com>
Subject: Re: [PATCH v2 05/14] PCI/AER: Add CXL PCIe port correctable error
 support in AER service driver

On Fri, 25 Oct 2024 16:02:56 -0500
Terry Bowman <terry.bowman@....com> wrote:

> The AER service driver doesn't currently handle CXL protocol errors
> reported by CXL root ports, CXL upstream switch ports, and CXL downstream
> switch ports. Consequently, RAS protocol errors from CXL PCIe port devices
> are not properly logged or handled.
> 
> These errors are reported to the OS via the root port's AER correctable
> and uncorrectable internal error fields. While the AER driver supports
> handling downstream port protocol errors in restricted CXL host (RCH) mode
> also known as CXL1.1, it lacks the same functionality for CXL PCIe ports
> operating in virtual hierarchy (VH) mode.
> 
> To address this gap, update the AER driver to handle CXL PCIe port device
> protocol correctable errors (CE).
> 
> Make this update alongside the existing downstream port RCH error handling
> logic, extending support to CXL PCIe ports in VH mode.
> 
> is_internal_error() is currently limited by CONFIG_PCIEAER_CXL kernel
> config. Update is_internal_error()'s function declaration such that it is
> always available regardless if CONFIG_PCIEAER_CXL kernel config is enabled
> or disabled.
> 
> The uncorrectable error (UCE) handling will be added in a future patch.
> 
> [1] CXL 3.1 Spec, 12.2.2 CXL Root Ports, Downstream Switch Ports, and
> Upstream Switch Ports
> 
> Signed-off-by: Terry Bowman <terry.bowman@....com>
This is a fiddly patch to read, but that's at least partly diff going crazy
in a few places.

Anyhow, I think it is fine but I would call out that this changes
things so that the PCI error handlers are no longer called for CXL ports
if it's an internal error.

With a sentence on that:

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

I'm not 100% convinced the path of separate handlers is the way to go
but we can always change things again if that doesn't work out.

Jonathan

> ---
>  drivers/pci/pcie/aer.c | 59 ++++++++++++++++++++++++++++--------------
>  1 file changed, 39 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 53e9a11f6c0f..1d3e5b929661 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -941,8 +941,15 @@ static bool find_source_device(struct pci_dev *parent,
>  	return true;
>  }
>  
> -#ifdef CONFIG_PCIEAER_CXL
> +static bool is_internal_error(struct aer_err_info *info)
> +{
> +	if (info->severity == AER_CORRECTABLE)
> +		return info->status & PCI_ERR_COR_INTERNAL;
>  
> +	return info->status & PCI_ERR_UNC_INTN;
> +}
> +
> +#ifdef CONFIG_PCIEAER_CXL

Diff was having fun.  Maybe put a blank line here? I think that's
what has tripped it up.

>  /**
>   * pci_aer_unmask_internal_errors - unmask internal errors
>   * @dev: pointer to the pcie_dev data structure
> @@ -994,14 +1001,6 @@ static bool cxl_error_is_native(struct pci_dev *dev)
>  	return (pcie_ports_native || host->native_aer);
>  }

> -

>  /**
> @@ -1115,8 +1131,11 @@ static void pci_aer_handle_error(struct pci_dev *dev, struct aer_err_info *info)
>  
>  static void handle_error_source(struct pci_dev *dev, struct aer_err_info *info)
>  {
> -	cxl_handle_error(dev, info);
> -	pci_aer_handle_error(dev, info);
> +	if (is_internal_error(info) && handles_cxl_errors(dev))
> +		cxl_handle_error(dev, info);
> +	else
> +		pci_aer_handle_error(dev, info);
Whilst not calling this for the CXL cases probably makes sense and
given new code needs to be the case to avoid a double clear I think,
I would call that change out more explicitly in the patch description.
> +

>  	pci_dev_put(dev);
>  }
>