This is a note to let you know that I've just added the patch titled
cxl/pci: Skip to handle RAS errors if CXL.mem device is detached
to the 6.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cxl-pci-skip-to-handle-ras-errors-if-cxl.mem-device-is-detached.patch
and it can be found in the queue-6.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From eef5c7b28dbecd6b141987a96db6c54e49828102 Mon Sep 17 00:00:00 2001
From: Li Ming <ming4.li@xxxxxxxxx>
Date: Mon, 29 Jan 2024 13:18:56 +0000
Subject: cxl/pci: Skip to handle RAS errors if CXL.mem device is detached
From: Li Ming <ming4.li@xxxxxxxxx>
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@xxxxxxxxxxxxxxx
Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Li Ming <ming4.li@xxxxxxxxx>
Link: https://lore.kernel.org/r/20240129131856.2458980-1-ming4.li@xxxxxxxxx
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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:
Patches currently in stable-queue which might be from ming4.li@xxxxxxxxx are
queue-6.7/cxl-pci-skip-to-handle-ras-errors-if-cxl.mem-device-is-detached.patch
