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Message-ID: <1a355946-8a5f-46b3-a8bb-37391fab304b@amd.com>
Date: Thu, 24 Apr 2025 10:03:31 -0500
From: "Bowman, Terry" <terry.bowman@....com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org, nifan.cxl@...il.com, 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, lukas@...ner.de,
ming.li@...omail.com, PradeepVineshReddy.Kodamati@....com
Subject: Re: [PATCH v8 05/16] PCI/AER: CXL driver dequeues CXL error forwarded
from AER service driver
On 4/23/2025 11:28 AM, Jonathan Cameron wrote:
> On Wed, 26 Mar 2025 20:47:06 -0500
> Terry Bowman <terry.bowman@....com> wrote:
>
>> The AER driver is now designed to forward CXL protocol errors to the CXL
>> driver. Update the CXL driver with functionality to dequeue the forwarded
>> CXL error from the kfifo. Also, update the CXL driver to process the CXL
>> protocol errors using CXL protocol error handlers.
>>
>> First, move cxl_rch_handle_error_iter() from aer.c to cxl/core/ras.c.
>> Remove and drop the cxl_rch_handle_error() in aer.c as it is not needed.
>>
>> Introduce function cxl_prot_err_work_fn() to dequeue work forwarded by the
>> AER service driver. This will begin the CXL protocol error processing
>> with the call to cxl_handle_prot_error().
>>
>> Introduce cxl_handle_prot_error() to differntiate between Restricted CXL
>> Host (RCH) protocol errors and CXL virtual host (VH) protocol errors.
>> RCH errors will be processed with a call to walk the associated Root
>> Complex Event Collector's (RCEC) secondary bus looking for the Root Complex
>> Integrated Endpoint (RCiEP) to handle the RCH error. Export pcie_walk_rcec()
>> so the CXL driver can walk the RCEC's downstream bus, searching for
>> the RCiEP.
>>
>> VH correctable error (CE) processing will call the CXL CE handler if
>> present. VH uncorrectable errors (UCE) will call cxl_do_recovery(),
>> implemented as a stub for now and to be updated in future patch. Export
>> pci_aer_clean_fatal_status() and pci_clean_device_status() used to clean up
>> AER status after handling.
>>
>> Create cxl_driver::error_handler structure similar to
>> pci_driver::error_handlers. Add handlers for CE and UCE CXL.io errors. Add
>> 'struct cxl_prot_error_info' as a parameter to the CXL CE and UCE error
>> handlers.
>>
>> Signed-off-by: Terry Bowman <terry.bowman@....com>
>> ---
>> drivers/cxl/core/ras.c | 102 +++++++++++++++++++++++++++++++++++++++-
>> drivers/cxl/cxl.h | 17 +++++++
>> drivers/pci/pci.c | 1 +
>> drivers/pci/pci.h | 6 ---
>> drivers/pci/pcie/aer.c | 42 +----------------
>> drivers/pci/pcie/rcec.c | 1 +
>> include/linux/aer.h | 2 +
>> include/linux/pci.h | 10 ++++
>> 8 files changed, 133 insertions(+), 48 deletions(-)
>>
>> diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c
>> index ecb60a5962de..eca8f11a05d9 100644
>> --- a/drivers/cxl/core/ras.c
>> +++ b/drivers/cxl/core/ras.c
>> @@ -139,8 +139,108 @@ int cxl_create_prot_err_info(struct pci_dev *_pdev, int severity,
>>
>> return 0;
>> }
>> +EXPORT_SYMBOL_NS_GPL(cxl_create_prot_err_info, "CXL");
>>
>> -struct work_struct cxl_prot_err_work;
>> +static void cxl_do_recovery(struct pci_dev *pdev) { }
>> +
>> +static int cxl_rch_handle_error_iter(struct pci_dev *pdev, void *data)
>> +{
>> + struct cxl_prot_error_info *err_info = data;
>> + const struct cxl_error_handlers *err_handler;
>> + struct device *dev = err_info->dev;
>> + struct cxl_driver *pdrv;
>> +
>> + /*
>> + * The capability, status, and control fields in Device 0,
>> + * Function 0 DVSEC control the CXL functionality of the
>> + * entire device (CXL 3.0, 8.1.3).
>> + */
>> + if (pdev->devfn != PCI_DEVFN(0, 0))
>> + return 0;
>> +
>> + /*
>> + * CXL Memory Devices must have the 502h class code set (CXL
>> + * 3.0, 8.1.12.1).
>> + */
>> + if ((pdev->class >> 8) != PCI_CLASS_MEMORY_CXL)
>> + return 0;
>> +
>> + if (!is_cxl_memdev(dev) || !dev->driver)
>> + return 0;
>> +
>> + pdrv = to_cxl_drv(dev->driver);
>> + if (!pdrv || !pdrv->err_handler)
>> + return 0;
>> +
>> + err_handler = pdrv->err_handler;
>> + if (err_info->severity == AER_CORRECTABLE) {
>> + if (err_handler->cor_error_detected)
>> + err_handler->cor_error_detected(dev, err_info);
>> + } else if (err_handler->error_detected) {
>> + cxl_do_recovery(pdev);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static void cxl_handle_prot_error(struct pci_dev *pdev, struct cxl_prot_error_info *err_info)
>> +{
>> + if (!pdev || !err_info)
> Are these real potential conditions? If so can we have a comment on why.
> If this is defensive only, do we need it?
> Looks like the caller below checked pdev already.
Yes, these checks can be removed.
>> + return;
>> +
>> + /*
>> + * Internal errors of an RCEC indicate an AER error in an
>> + * RCH's downstream port. Check and handle them in the CXL.mem
>> + * device driver.
>> + */
>> + if (pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_EC)
>> + return pcie_walk_rcec(pdev, cxl_rch_handle_error_iter, err_info);
>> +
>> + if (err_info->severity == AER_CORRECTABLE) {
>> + struct device *dev __free(put_device) = get_device(err_info->dev);
> Similar question around lifetimes. The caller already got this. Why again?
Not necessary. I'll remove.
>> + struct cxl_driver *pdrv;
> calling a cxl driver pdrv seems odd. cdrv maybe?
Ok. I'll rename cdrv.
>> + int aer = pdev->aer_cap;
>> +
>> + if (!dev || !dev->driver)
>> + return;
>> +
>> + if (aer) {
>> + int ras_status;
>> +
>> + pci_read_config_dword(pdev, aer + PCI_ERR_COR_STATUS, &ras_status);
> If we get multiple bits set in this register, can this wipe out ones we haven't noticed
> anywhere else in the handling? Bad tlp etc. Maybe we need to ensure this only clears
> the internal error bit?
Good point. I'll fix. I'm going to rename 'ras_status' to 'aer_status' as well.
>> + pci_write_config_dword(pdev, aer + PCI_ERR_COR_STATUS,
>> + ras_status);
>> + }
>> +
>> + pdrv = to_cxl_drv(dev->driver);
>> + if (!pdrv || !pdrv->err_handler ||
>> + !pdrv->err_handler->cor_error_detected)
>> + return;
>> +
>> + pdrv->err_handler->cor_error_detected(dev, err_info);
>> + pcie_clear_device_status(pdev);
>> + } else {
>> + cxl_do_recovery(pdev);
>> + }
>> +}
>> +
>> +static void cxl_prot_err_work_fn(struct work_struct *work)
>> +{
>> + struct cxl_prot_err_work_data wd;
>> +
>> + while (cxl_prot_err_kfifo_get(&wd)) {
>> + struct cxl_prot_error_info *err_info = &wd.err_info;
>> + struct device *dev __free(put_device) = get_device(err_info->dev);
>> + struct pci_dev *pdev __free(pci_dev_put) = pci_dev_get(err_info->pdev);
>> +
>> + if (!dev || !pdev)
>> + continue;
>> +
>> + cxl_handle_prot_error(pdev, err_info);
>> + }
>> +}
>> +
>> +static DECLARE_WORK(cxl_prot_err_work, cxl_prot_err_work_fn);
> Ah! Here it is... I think this can be in patch 3. With a stub of the function
> (which is what the patch 3 description claims is there).
I'll move it.
>>
> Jonathan
>
-Terry
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