6.7-stable review patch. If anyone has any objections, please let me know.
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From: Li Ming ming4.li@intel.com
commit eef5c7b28dbecd6b141987a96db6c54e49828102 upstream.
The PCI AER model is an awkward fit for CXL error handling. While the expectation is that a PCI device can escalate to link reset to recover from an AER event, the same reset on CXL amounts to a surprise memory hotplug of massive amounts of memory.
At present, the CXL error handler attempts some optimistic error handling to unbind the device from the cxl_mem driver after reaping some RAS register values. This results in a "hopeful" attempt to unplug the memory, but there is no guarantee that will succeed.
A subsequent AER notification after the memdev unbind event can no longer assume the registers are mapped. Check for memdev bind before reaping status register values to avoid crashes of the form:
BUG: unable to handle page fault for address: ffa00000195e9100 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page [...] RIP: 0010:__cxl_handle_ras+0x30/0x110 [cxl_core] [...] Call Trace: <TASK> ? __die+0x24/0x70 ? page_fault_oops+0x82/0x160 ? kernelmode_fixup_or_oops+0x84/0x110 ? exc_page_fault+0x113/0x170 ? asm_exc_page_fault+0x26/0x30 ? __pfx_dpc_reset_link+0x10/0x10 ? __cxl_handle_ras+0x30/0x110 [cxl_core] ? find_cxl_port+0x59/0x80 [cxl_core] cxl_handle_rp_ras+0xbc/0xd0 [cxl_core] cxl_error_detected+0x6c/0xf0 [cxl_core] report_error_detected+0xc7/0x1c0 pci_walk_bus+0x73/0x90 pcie_do_recovery+0x23f/0x330
Longer term, the unbind and PCI_ERS_RESULT_DISCONNECT behavior might need to be replaced with a new PCI_ERS_RESULT_PANIC.
Fixes: 6ac07883dbb5 ("cxl/pci: Add RCH downstream port error logging") Cc: stable@vger.kernel.org Suggested-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Li Ming ming4.li@intel.com Link: https://lore.kernel.org/r/20240129131856.2458980-1-ming4.li@intel.com Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/cxl/core/pci.c | 43 +++++++++++++++++++++++++++++++------------ 1 file changed, 31 insertions(+), 12 deletions(-)
--- a/drivers/cxl/core/pci.c +++ b/drivers/cxl/core/pci.c @@ -931,11 +931,21 @@ static void cxl_handle_rdport_errors(str void cxl_cor_error_detected(struct pci_dev *pdev) { struct cxl_dev_state *cxlds = pci_get_drvdata(pdev); + struct device *dev = &cxlds->cxlmd->dev;
- if (cxlds->rcd) - cxl_handle_rdport_errors(cxlds); + scoped_guard(device, dev) { + if (!dev->driver) { + dev_warn(&pdev->dev, + "%s: memdev disabled, abort error handling\n", + dev_name(dev)); + return; + }
- cxl_handle_endpoint_cor_ras(cxlds); + if (cxlds->rcd) + cxl_handle_rdport_errors(cxlds); + + cxl_handle_endpoint_cor_ras(cxlds); + } } EXPORT_SYMBOL_NS_GPL(cxl_cor_error_detected, CXL);
@@ -947,16 +957,25 @@ pci_ers_result_t cxl_error_detected(stru struct device *dev = &cxlmd->dev; bool ue;
- if (cxlds->rcd) - cxl_handle_rdport_errors(cxlds); + scoped_guard(device, dev) { + if (!dev->driver) { + dev_warn(&pdev->dev, + "%s: memdev disabled, abort error handling\n", + dev_name(dev)); + return PCI_ERS_RESULT_DISCONNECT; + } + + if (cxlds->rcd) + cxl_handle_rdport_errors(cxlds); + /* + * A frozen channel indicates an impending reset which is fatal to + * CXL.mem operation, and will likely crash the system. On the off + * chance the situation is recoverable dump the status of the RAS + * capability registers and bounce the active state of the memdev. + */ + ue = cxl_handle_endpoint_ras(cxlds); + }
- /* - * A frozen channel indicates an impending reset which is fatal to - * CXL.mem operation, and will likely crash the system. On the off - * chance the situation is recoverable dump the status of the RAS - * capability registers and bounce the active state of the memdev. - */ - ue = cxl_handle_endpoint_ras(cxlds);
switch (state) { case pci_channel_io_normal: