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Message-ID: <20250612121704.0000498e@huawei.com>
Date: Thu, 12 Jun 2025 12:17:04 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Dave Jiang <dave.jiang@...el.com>
CC: "Bowman, Terry" <terry.bowman@....com>,
<PradeepVineshReddy.Kodamati@....com>, <dave@...olabs.net>,
<alison.schofield@...el.com>, <vishal.l.verma@...el.com>,
<ira.weiny@...el.com>, <dan.j.williams@...el.com>, <bhelgaas@...gle.com>,
<bp@...en8.de>, <ming.li@...omail.com>, <shiju.jose@...wei.com>,
<dan.carpenter@...aro.org>, <Smita.KoralahalliChannabasappa@....com>,
<kobayashi.da-06@...itsu.com>, <rrichter@....com>, <peterz@...radead.org>,
<linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-pci@...r.kernel.org>
Subject: Re: [PATCH v9 04/16] PCI/AER: Dequeue forwarded CXL error
On Mon, 9 Jun 2025 13:34:31 -0700
Dave Jiang <dave.jiang@...el.com> wrote:
> On 6/9/25 12:57 PM, Bowman, Terry wrote:
> >
> >
> > On 6/6/2025 5:43 PM, Dave Jiang wrote:
> >>
> >> On 6/6/25 11:14 AM, Bowman, Terry wrote:
> >>>
> >>> On 6/6/2025 10:57 AM, Dave Jiang wrote:
> >>>> On 6/3/25 10:22 AM, Terry Bowman 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 begin the protocol
> >>>>> error handling processing using the work received from the FIFO.
> >>>>>
> >>>>> 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 a call to cxl_handle_prot_error().
> >>>>>
> >>>>> Update cxl/core/ras.c by adding cxl_rch_handle_error_iter() that was
> >>>>> previously in the AER driver.
> >>>>>
> >>>>> Introduce sbdf_to_pci() to take the SBDF values from 'struct cxl_prot_error_info'
> >>>>> and use in discovering the erring PCI device. Make scope based reference
> >>>>> increments/decrements for the discovered PCI device and the associated
> >>>>> CXL device.
> >>>>>
> >>>>> Implement cxl_handle_prot_error() to differentiate 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. 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.
> >>>>>
> >>>>> Signed-off-by: Terry Bowman <terry.bowman@....com>
> >>>>> ---
> >>>>> drivers/cxl/core/ras.c | 92 +++++++++++++++++++++++++++++++++++++++++
> >>>>> drivers/pci/pci.c | 1 +
> >>>>> drivers/pci/pci.h | 8 ----
> >>>>> drivers/pci/pcie/aer.c | 1 +
> >>>>> drivers/pci/pcie/rcec.c | 1 +
> >>>>> include/linux/aer.h | 2 +
> >>>>> include/linux/pci.h | 10 +++++
> >>>>> 7 files changed, 107 insertions(+), 8 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c
> >>>>> index d35525e79e04..9ed5c682e128 100644
> >>>>> --- a/drivers/cxl/core/ras.c
> >>>>> +++ b/drivers/cxl/core/ras.c
> >>>>> @@ -110,8 +110,100 @@ static DECLARE_WORK(cxl_cper_prot_err_work, cxl_cper_prot_err_work_fn);
> >>>>>
> >>>>> #ifdef CONFIG_PCIEAER_CXL
> >>>>>
> >>>>> +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;
> >>>>> + struct pci_dev *pdev_ref __free(pci_dev_put) = pci_dev_get(pdev);
> >>>>> + struct cxl_dev_state *cxlds;
> >>>>> +
> >>>>> + /*
> >>>>> + * 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)
> >>>> Should use FIELD_GET() to be consistent with the rest of CXL code base
> >>> Ok.
> >
> > Hi Dave,
> >
> > I have a question. I found I need to do the same you recommended for is_cxl_mem_dev() in
> > drivers/pci/pcie/cxl_aer.c. Looks like I need to define:
> >
> > #define PCI_CLASS_CODE_MASK GENMASK(23, 8)
> >
> > to be used as:
> >
> > FIELD_GET(PCI_CLASS_CODE_MASK, pdev->class)
> >
> > What header file can I add the PCI_CLASS_CODE_MASK #define so that it can be used in CXL
> > and PCI drivers?
>
> Perhaps include/uapi/linux/pci_regs.h? Although you may need to define the raw mask instead of using GENMASK due to the header being exported to user as well.
>
It's messy because that register has 3 fields (at least it does by 6.2 - not sure about earlier)
and we are matching on combination of "sub class code" and "base class code" but not the programming
interface which is the bottom 8 bits.
Whilst I'd kind like this cleaned up naming a mask might be a pain...
Maybe we can get away with PCI_CLASS_CODE_MASK given how we name the
specific IDs but perhaps making it kernel internal via include/linux/pci_ids.h
is safer than an include in uapi?
I'd also like to see such a macro used through out the kernel and not
just in this one place.
Jonathan
> DJ
>
> >
> > Terry
> >
> >
> >>>>> + return 0;
> >>>>> +
> >>>>> + if (!is_cxl_memdev(&pdev->dev) || !pdev->dev.driver)
> >>>> I think you need to hold the pdev->dev lock while checking if the driver exists.
> >>> Ok.
> >>>>> + return 0;
> >>>>> +
> >>>>> + cxlds = pci_get_drvdata(pdev);
> >>>>> + struct device *dev __free(put_device) = get_device(&cxlds->cxlmd->dev);
> >>>> Maybe a comment on why cxlmd->dev ref is needed here.
> >>> Good point.
> >>>>> +
> >>>>> + if (err_info->severity == AER_CORRECTABLE)
> >>>>> + cxl_cor_error_detected(pdev);
> >>>>> + else
> >>>>> + cxl_do_recovery(pdev);
> >>>>> +
> >>>>> + return 1;
> >>>>> +}
> >>>>> +
> >>>>> +static struct pci_dev *sbdf_to_pci(struct cxl_prot_error_info *err_info)
> >>>>> +{
> >>>>> + unsigned int devfn = PCI_DEVFN(err_info->device,
> >>>>> + err_info->function);
> >>>>> + struct pci_dev *pdev __free(pci_dev_put) =
> >>>>> + pci_get_domain_bus_and_slot(err_info->segment,
> >>>>> + err_info->bus,
> >>>>> + devfn);
> >>>> Looks like DanC already caught that. Maybe have this function return with a ref held. I would also add a comment for the function mention that the caller need to put the device.
> >>> Right. I made the change in v10 source after DanC commented. I'll add a comment that callers must decrement the reference count..
> >>>>> + return pdev;
> >>>>> +}
> >>>>> +
> >>>>> +static void cxl_handle_prot_error(struct cxl_prot_error_info *err_info)
> >>>>> +{
> >>>>> + struct pci_dev *pdev __free(pci_dev_put) = pci_dev_get(sbdf_to_pci(err_info));
> >>>>> +
> >>>>> + if (!pdev) {
> >>>>> + pr_err("Failed to find the CXL device\n");
> >>>>> + 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);
> >>>>> +
> >>>> cxl_rch_handle_error_iter() holds the pdev device lock when handling errors. Does the code block below need locking?
> >>>>
> >>>> DJ
> >>> There is a guard_lock() in the EP CXL error handlers (cxl_error_detected()/cxl_cor_error_detected()). I have question about
> >>> the same for the non-EP handlers added later: should we add the same guard() for the CXL port handlers? That is in following patch:
> >>> [PATCH v9 13/16] cxl/pci: Introduce CXL Port protocol error handlers.
> >> I would think so....
> >>
> >> DJ
> >>
> >>> Terry
> >>>>> + if (err_info->severity == AER_CORRECTABLE) {
> >>>>> + int aer = pdev->aer_cap;
> >>>>> + struct cxl_dev_state *cxlds = pci_get_drvdata(pdev);
> >>>>> + struct device *dev __free(put_device) = get_device(&cxlds->cxlmd->dev);
> >>>>> +
> >>>>> + if (aer)
> >>>>> + pci_clear_and_set_config_dword(pdev,
> >>>>> + aer + PCI_ERR_COR_STATUS,
> >>>>> + 0, PCI_ERR_COR_INTERNAL);
> >>>>> +
> >>>>> + cxl_cor_error_detected(pdev);
> >>>>> +
> >>>>> + 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;
> >>>>> +
> >>>>> + cxl_handle_prot_error(err_info);
> >>>>> + }
> >>>>> }
> >>>>>
> >>>>> #else
> >>>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> >>>>> index e77d5b53c0ce..524ac32b744a 100644
> >>>>> --- a/drivers/pci/pci.c
> >>>>> +++ b/drivers/pci/pci.c
> >>>>> @@ -2328,6 +2328,7 @@ void pcie_clear_device_status(struct pci_dev *dev)
> >>>>> pcie_capability_read_word(dev, PCI_EXP_DEVSTA, &sta);
> >>>>> pcie_capability_write_word(dev, PCI_EXP_DEVSTA, sta);
> >>>>> }
> >>>>> +EXPORT_SYMBOL_NS_GPL(pcie_clear_device_status, "CXL");
> >>>>> #endif
> >>>>>
> >>>>> /**
> >>>>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> >>>>> index d6296500b004..3c54a5ed803e 100644
> >>>>> --- a/drivers/pci/pci.h
> >>>>> +++ b/drivers/pci/pci.h
> >>>>> @@ -649,16 +649,10 @@ static inline bool pci_dpc_recovered(struct pci_dev *pdev) { return false; }
> >>>>> void pci_rcec_init(struct pci_dev *dev);
> >>>>> void pci_rcec_exit(struct pci_dev *dev);
> >>>>> void pcie_link_rcec(struct pci_dev *rcec);
> >>>>> -void pcie_walk_rcec(struct pci_dev *rcec,
> >>>>> - int (*cb)(struct pci_dev *, void *),
> >>>>> - void *userdata);
> >>>>> #else
> >>>>> static inline void pci_rcec_init(struct pci_dev *dev) { }
> >>>>> static inline void pci_rcec_exit(struct pci_dev *dev) { }
> >>>>> static inline void pcie_link_rcec(struct pci_dev *rcec) { }
> >>>>> -static inline void pcie_walk_rcec(struct pci_dev *rcec,
> >>>>> - int (*cb)(struct pci_dev *, void *),
> >>>>> - void *userdata) { }
> >>>>> #endif
> >>>>>
> >>>>> #ifdef CONFIG_PCI_ATS
> >>>>> @@ -967,7 +961,6 @@ void pci_no_aer(void);
> >>>>> void pci_aer_init(struct pci_dev *dev);
> >>>>> void pci_aer_exit(struct pci_dev *dev);
> >>>>> extern const struct attribute_group aer_stats_attr_group;
> >>>>> -void pci_aer_clear_fatal_status(struct pci_dev *dev);
> >>>>> int pci_aer_clear_status(struct pci_dev *dev);
> >>>>> int pci_aer_raw_clear_status(struct pci_dev *dev);
> >>>>> void pci_save_aer_state(struct pci_dev *dev);
> >>>>> @@ -976,7 +969,6 @@ void pci_restore_aer_state(struct pci_dev *dev);
> >>>>> static inline void pci_no_aer(void) { }
> >>>>> static inline void pci_aer_init(struct pci_dev *d) { }
> >>>>> static inline void pci_aer_exit(struct pci_dev *d) { }
> >>>>> -static inline void pci_aer_clear_fatal_status(struct pci_dev *dev) { }
> >>>>> static inline int pci_aer_clear_status(struct pci_dev *dev) { return -EINVAL; }
> >>>>> static inline int pci_aer_raw_clear_status(struct pci_dev *dev) { return -EINVAL; }
> >>>>> static inline void pci_save_aer_state(struct pci_dev *dev) { }
> >>>>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> >>>>> index 5350fa5be784..6e88331c6303 100644
> >>>>> --- a/drivers/pci/pcie/aer.c
> >>>>> +++ b/drivers/pci/pcie/aer.c
> >>>>> @@ -290,6 +290,7 @@ void pci_aer_clear_fatal_status(struct pci_dev *dev)
> >>>>> if (status)
> >>>>> pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_STATUS, status);
> >>>>> }
> >>>>> +EXPORT_SYMBOL_GPL(pci_aer_clear_fatal_status);
> >>>>>
> >>>>> /**
> >>>>> * pci_aer_raw_clear_status - Clear AER error registers.
> >>>>> diff --git a/drivers/pci/pcie/rcec.c b/drivers/pci/pcie/rcec.c
> >>>>> index d0bcd141ac9c..fb6cf6449a1d 100644
> >>>>> --- a/drivers/pci/pcie/rcec.c
> >>>>> +++ b/drivers/pci/pcie/rcec.c
> >>>>> @@ -145,6 +145,7 @@ void pcie_walk_rcec(struct pci_dev *rcec, int (*cb)(struct pci_dev *, void *),
> >>>>>
> >>>>> walk_rcec(walk_rcec_helper, &rcec_data);
> >>>>> }
> >>>>> +EXPORT_SYMBOL_NS_GPL(pcie_walk_rcec, "CXL");
> >>>>>
> >>>>> void pci_rcec_init(struct pci_dev *dev)
> >>>>> {
> >>>>> diff --git a/include/linux/aer.h b/include/linux/aer.h
> >>>>> index 550407240ab5..c9a18eca16f8 100644
> >>>>> --- a/include/linux/aer.h
> >>>>> +++ b/include/linux/aer.h
> >>>>> @@ -77,12 +77,14 @@ struct cxl_prot_err_work_data {
> >>>>>
> >>>>> #if defined(CONFIG_PCIEAER)
> >>>>> int pci_aer_clear_nonfatal_status(struct pci_dev *dev);
> >>>>> +void pci_aer_clear_fatal_status(struct pci_dev *dev);
> >>>>> int pcie_aer_is_native(struct pci_dev *dev);
> >>>>> #else
> >>>>> static inline int pci_aer_clear_nonfatal_status(struct pci_dev *dev)
> >>>>> {
> >>>>> return -EINVAL;
> >>>>> }
> >>>>> +static inline void pci_aer_clear_fatal_status(struct pci_dev *dev) { }
> >>>>> static inline int pcie_aer_is_native(struct pci_dev *dev) { return 0; }
> >>>>> #endif
> >>>>>
> >>>>> diff --git a/include/linux/pci.h b/include/linux/pci.h
> >>>>> index bff3009f9ff0..cd53715d53f3 100644
> >>>>> --- a/include/linux/pci.h
> >>>>> +++ b/include/linux/pci.h
> >>>>> @@ -1806,6 +1806,9 @@ extern bool pcie_ports_native;
> >>>>>
> >>>>> int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
> >>>>> bool use_lt);
> >>>>> +void pcie_walk_rcec(struct pci_dev *rcec,
> >>>>> + int (*cb)(struct pci_dev *, void *),
> >>>>> + void *userdata);
> >>>>> #else
> >>>>> #define pcie_ports_disabled true
> >>>>> #define pcie_ports_native false
> >>>>> @@ -1816,8 +1819,15 @@ static inline int pcie_set_target_speed(struct pci_dev *port,
> >>>>> {
> >>>>> return -EOPNOTSUPP;
> >>>>> }
> >>>>> +
> >>>>> +static inline void pcie_walk_rcec(struct pci_dev *rcec,
> >>>>> + int (*cb)(struct pci_dev *, void *),
> >>>>> + void *userdata) { }
> >>>>> +
> >>>>> #endif
> >>>>>
> >>>>> +void pcie_clear_device_status(struct pci_dev *dev);
> >>>>> +
> >>>>> #define PCIE_LINK_STATE_L0S (BIT(0) | BIT(1)) /* Upstr/dwnstr L0s */
> >>>>> #define PCIE_LINK_STATE_L1 BIT(2) /* L1 state */
> >>>>> #define PCIE_LINK_STATE_L1_1 BIT(3) /* ASPM L1.1 state */
> >>>
> >
>
>
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