From 2bc6b218717b9d08f466f88209251d54bc09b207 Mon Sep 17 00:00:00 2001
From: Fuad Tabba <fuad.tabba@linux.dev>
Date: Tue, 22 Sep 2026 19:14:30 +0100
Subject: arm64/boot: Disable trapping of PMZR_EL0 writes to EL2

__init_el2_fgt2() writes one mask to both HDFGRTR2_EL2 and HDFGWTR2_EL2.
PMZR_EL0 is write-only, so its trap bit, nPMZR_EL0, exists only in
HDFGWTR2_EL2 and is therefore never set: a PMZR_EL0 write from the host
traps to EL2, where the nVHE hypervisor has no handler and BUG()s. The
kernel never writes PMZR_EL0, but kernel.perf_user_access=1 has the PMU
driver set PMUSERENR_EL0.UEN for a task with a user-read event, so a
write from EL0 reaches the trap and takes the host down without a panic
message.

Accumulate the HDFGWTR2_EL2 bits separately, as __init_el2_fgt() already
does for HDFGWTR_EL2, and set nPMZR_EL0 with the other FEAT_PMUv3p9
bits.

Fixes: 858c7bfcb35e1 ("arm64/boot: Enable EL2 requirements for FEAT_PMUv3p9")
Cc: stable@vger.kernel.org
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Oliver Upton <oupton@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
 Documentation/driver-api/w1.rst | 67 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 Documentation/driver-api/w1.rst

(limited to 'Documentation/driver-api/w1.rst')

diff --git a/Documentation/driver-api/w1.rst b/Documentation/driver-api/w1.rst
new file mode 100644
index 000000000..bda3ad60f
--- /dev/null
+++ b/Documentation/driver-api/w1.rst
@@ -0,0 +1,67 @@
+======================
+W1: Dallas' 1-wire bus
+======================
+
+:Author: David Fries
+
+W1 API internal to the kernel
+=============================
+
+include/linux/w1.h
+~~~~~~~~~~~~~~~~~~
+
+W1 kernel API functions.
+
+.. kernel-doc:: include/linux/w1.h
+   :internal:
+
+drivers/w1/w1.c
+~~~~~~~~~~~~~~~
+
+W1 core functions.
+
+.. kernel-doc:: drivers/w1/w1.c
+   :internal:
+
+drivers/w1/w1_family.c
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Allows registering device family operations.
+
+.. kernel-doc:: drivers/w1/w1_family.c
+   :export:
+
+drivers/w1/w1_internal.h
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+W1 internal initialization for master devices.
+
+.. kernel-doc:: drivers/w1/w1_internal.h
+   :internal:
+
+drivers/w1/w1_int.c
+~~~~~~~~~~~~~~~~~~~~
+
+W1 internal initialization for master devices.
+
+.. kernel-doc:: drivers/w1/w1_int.c
+   :export:
+
+drivers/w1/w1_netlink.h
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+W1 external netlink API structures and commands.
+
+.. kernel-doc:: drivers/w1/w1_netlink.h
+   :internal:
+
+drivers/w1/w1_io.c
+~~~~~~~~~~~~~~~~~~~
+
+W1 input/output.
+
+.. kernel-doc:: drivers/w1/w1_io.c
+   :export:
+
+.. kernel-doc:: drivers/w1/w1_io.c
+   :internal:
-- 
cgit v1.3.1