This is a note to let you know that I've just added the patch titled
cxl/hdm: Fix dpa translation locking
to the 6.6-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-hdm-fix-dpa-translation-locking.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6f5c4eca48ffe18307b4e1d375817691c9005c87 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@xxxxxxxxx>
Date: Wed, 6 Dec 2023 19:11:14 -0800
Subject: cxl/hdm: Fix dpa translation locking
From: Dan Williams <dan.j.williams@xxxxxxxxx>
commit 6f5c4eca48ffe18307b4e1d375817691c9005c87 upstream.
The helper, cxl_dpa_resource_start(), snapshots the dpa-address of an
endpoint-decoder after acquiring the cxl_dpa_rwsem. However, it is
sufficient to assert that cxl_dpa_rwsem is held rather than acquire it
in the helper. Otherwise, it triggers multiple lockdep reports:
1/ Tracing callbacks are in an atomic context that can not acquire sleeping
locks:
BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1525
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1288, name: bash
preempt_count: 2, expected: 0
RCU nest depth: 0, expected: 0
[..]
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20230524-3.fc38 05/24/2023
Call Trace:
<TASK>
dump_stack_lvl+0x71/0x90
__might_resched+0x1b2/0x2c0
down_read+0x1a/0x190
cxl_dpa_resource_start+0x15/0x50 [cxl_core]
cxl_trace_hpa+0x122/0x300 [cxl_core]
trace_event_raw_event_cxl_poison+0x1c9/0x2d0 [cxl_core]
2/ The rwsem is already held in the inject poison path:
WARNING: possible recursive locking detected
6.7.0-rc2+ #12 Tainted: G W OE N
--------------------------------------------
bash/1288 is trying to acquire lock:
ffffffffc05f73d0 (cxl_dpa_rwsem){++++}-{3:3}, at: cxl_dpa_resource_start+0x15/0x50 [cxl_core]
but task is already holding lock:
ffffffffc05f73d0 (cxl_dpa_rwsem){++++}-{3:3}, at: cxl_inject_poison+0x7d/0x1e0 [cxl_core]
[..]
Call Trace:
<TASK>
dump_stack_lvl+0x71/0x90
__might_resched+0x1b2/0x2c0
down_read+0x1a/0x190
cxl_dpa_resource_start+0x15/0x50 [cxl_core]
cxl_trace_hpa+0x122/0x300 [cxl_core]
trace_event_raw_event_cxl_poison+0x1c9/0x2d0 [cxl_core]
__traceiter_cxl_poison+0x5c/0x80 [cxl_core]
cxl_inject_poison+0x1bc/0x1e0 [cxl_core]
This appears to have been an issue since the initial implementation and
uncovered by the new cxl-poison.sh test [1]. That test is now passing with
these changes.
Fixes: 28a3ae4ff66c ("cxl/trace: Add an HPA to cxl_poison trace events")
Link: http://lore.kernel.org/r/e4f2716646918135ddbadf4146e92abb659de734.1700615159.git.alison.schofield@xxxxxxxxx [1]
Cc: <stable@xxxxxxxxxxxxxxx>
Cc: Alison Schofield <alison.schofield@xxxxxxxxx>
Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/cxl/core/hdm.c | 3 +--
drivers/cxl/core/port.c | 4 ++--
2 files changed, 3 insertions(+), 4 deletions(-)
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -373,10 +373,9 @@ resource_size_t cxl_dpa_resource_start(s
{
resource_size_t base = -1;
- down_read(&cxl_dpa_rwsem);
+ lockdep_assert_held(&cxl_dpa_rwsem);
if (cxled->dpa_res)
base = cxled->dpa_res->start;
- up_read(&cxl_dpa_rwsem);
return base;
}
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -219,9 +219,9 @@ static ssize_t dpa_resource_show(struct
char *buf)
{
struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);
- u64 base = cxl_dpa_resource_start(cxled);
- return sysfs_emit(buf, "%#llx\n", base);
+ guard(rwsem_read)(&cxl_dpa_rwsem);
+ return sysfs_emit(buf, "%#llx\n", (u64)cxl_dpa_resource_start(cxled));
}
static DEVICE_ATTR_RO(dpa_resource);
Patches currently in stable-queue which might be from dan.j.williams@xxxxxxxxx are
queue-6.6/cxl-hdm-fix-dpa-translation-locking.patch
