linux-stable.git/Documentation, branch v7.1.5

cpu/hotplug: Fix NULL kobject warning in cpuhp_smt_enable()

2026-07-24T14:21:20+00:00

commit f9a82544c7174851f5c7524622f5966dcafd3a47 upstream.

On arm64, when booting with `maxcpus` greater than the number of present
CPUs (e.g., QEMU -smp cpus=4,maxcpus=8), some CPUs are marked as 'present'
but have not yet been registered via register_cpu(). Consequently,
the per-cpu device objects for these CPUs are not yet initialized.

In cpuhp_smt_enable(), the code iterates over all present CPUs. Calling
_cpu_up() for these unregistered CPUs eventually leads to
sysfs_create_group() being called with a NULL kobject (or a kobject
without a directory), triggering the following warning in
fs/sysfs/group.c:

  WARNING: fs/sysfs/group.c:137 at internal_create_group+0x41c/0x4bc, CPU#2: sh/181
  [...]
  Call trace:
    internal_create_group+0x41c/0x4bc (P)
    sysfs_create_group+0x18/0x24
    topology_add_dev+0x1c/0x28
    cpuhp_invoke_callback+0x104/0x20c
    __cpuhp_invoke_callback_range+0x94/0x11c
    _cpu_up+0x200/0x37c

When booting with ACPI, arm64 smp_prepare_cpus() currently sets all
enumerated CPUs as "present" regardless of their status in the MADT. This
causes issues with SMT hotplug control. For instance, with QEMU's
"-smp 4,maxcpus=8" configuration, the MADT GICC entries are populated as
follows:

1. The first four CPUs: `Enabled` set but `Online Capable` not set.

2. The remaining four CPUs: `Online Capable` set but `Enabled` not set
   to support potential hot-plugging.

Fix this by:

1. When booting with ACPI, checking the ACPI_MADT_ENABLED flag in the GICC
   entry before calling set_cpu_present() during SMP initialization.

2. Properly managing the present mask in acpi_map_cpu() and
   acpi_unmap_cpu() to support actual CPU hotplug events, This aligns with
   other architectures like x86 and LoongArch.

3. Update the arm64 CPU hotplug documentation to no longer state that all
   online-capable vCPUs are marked as present by the kernel at boot time.

This ensures that only physically available or explicitly enabled CPUs
are in the present mask, keeping the SMT control logic consistent with
the actual hardware state.

Cc: Catalin Marinas 
Cc: Jonathan Cameron 
Cc: James Morse 
Cc: Yicong Yang 
Cc: stable@vger.kernel.org
Link: https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#gic-cpu-interface-gicc-structure
Fixes: eed4583bcf9a ("arm64: Kconfig: Enable HOTPLUG_SMT")
Reviewed-by: Catalin Marinas 
Suggested-by: Catalin Marinas 
Signed-off-by: Jinjie Ruan 
Signed-off-by: Will Deacon 
Signed-off-by: Greg Kroah-Hartman

tracing/eprobes: Allow use of BTF names to dereference pointers

2026-07-24T14:20:35+00:00

[ Upstream commit 69efd863a78584b9416ed6be0e1e7349124b4a00 ]

Add syntax to the parsing of eprobes to be able to typecast a trace event
field that is a pointer to a structure.

Currently, a dereference must be a number, where the user has to figure
out manually the offset of a member of a structure that they want to
dereference.

But for event probes that records a field that happens to be a pointer to
a structure, it cannot dereference these values with BTF naming, but
must use numerical offsets.

For example, to find out what device a sk_buff is pointing to in the
net_dev_xmit trace event, one must first use gdb to find the offsets of the
members of the structures:

 (gdb) p &((struct sk_buff *)0)->dev
 $1 = (struct net_device **) 0x10
 (gdb) p &((struct net_device *)0)->name
 $2 = (char (*)[16]) 0x118

And then use the raw numbers to dereference:

  # echo 'e:xmit net.net_dev_xmit +0x118(+0x10($skbaddr)):string' >> dynamic_events

If BTF is in the kernel, then instead, the skbaddr can be typecast to
sk_buff and use the normal dereference logic.

  # echo 'e:xmit net.net_dev_xmit (sk_buff)skbaddr->dev->name:string' >> dynamic_events
  # echo 1 > events/eprobes/xmit/enable
  # cat trace
[..]
    sshd-session-1022    [000] b..2.   860.249343: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.250061: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.250142: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.263553: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.283820: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.302716: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.322905: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.342828: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.362268: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.382335: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.400856: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.419893: xmit: (net.net_dev_xmit) arg1="enp7s0"

The syntax is simply: (STRUCT)(FIELD)->MEMBER[->MEMBER..]

Also add comments around the #else and #endif of #ifdef CONFIG_PROBE_EVENTS_BTF_ARGS
to know what they are for.

Link: https://lore.kernel.org/all/20260601130746.2139d926@gandalf.local.home/

Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Masami Hiramatsu (Google) 
Stable-dep-of: 251a8fe1b9ae ("tracing/probes: Remove WARN_ON_ONCE from parse_btf_arg")
Signed-off-by: Sasha Levin

dt-bindings: net: renesas,ether: Drop example "ethernet-phy-ieee802.3-c22" fallback

2026-07-24T14:20:31+00:00

[ Upstream commit 14eb1d2c03b38ce3427f299967f7a4d97ebff4c2 ]

Fix the Micrel PHY in the example which shouldn't have the
fallback "ethernet-phy-ieee802.3-c22" compatible:

Documentation/devicetree/bindings/net/renesas,ether.example.dtb: ethernet-phy@1 \
  (ethernet-phy-id0022.1537): compatible: ['ethernet-phy-id0022.1537', 'ethernet-phy-ieee802.3-c22'] is too long
        from schema $id: http://devicetree.org/schemas/net/micrel.yaml

Signed-off-by: Rob Herring (Arm) 
Reviewed-by: Andrew Lunn 
Acked-by: Conor Dooley 
Acked-by: Niklas Söderlund 
Fixes: 37a2fce09001 ("dt-bindings: sh_eth convert bindings to json-schema")
Link: https://patch.msgid.link/20260624150250.131966-2-robh@kernel.org
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin

Docs/driver-api/uio-howto: document mmap_prepare callback

2026-07-24T14:20:28+00:00

[ Upstream commit de5c46373eb8148aa92c024cf30d26a6d495e278 ]

The UIO howto still documents an mmap callback in struct uio_info.
That field was replaced by mmap_prepare, which takes a struct
vm_area_desc.

A UIO driver following the current howto no longer builds because
struct uio_info has no mmap member. Update the documented callback
signature and matching text to match the current API.

Fixes: 933f05f58ac6 ("uio: replace deprecated mmap hook with mmap_prepare in uio_info")
Signed-off-by: Doehyun Baek 
Reviewed-by: Lorenzo Stoakes 
Acked-by: Randy Dunlap 
Signed-off-by: Jonathan Corbet 
Message-ID: <20260622181821.1195257-1-doehyunbaek@gmail.com>
Signed-off-by: Sasha Levin

Documentation: ABI: sysfs-class-reboot-mode-reboot_modes: fix doc warnings

2026-07-24T14:20:12+00:00

[ Upstream commit a888754e51e915731c8974c4d6d62709facb35d3 ]

Repair the docs build warnings in this file by unindenting the description,
adding blank lines, and using `` to quote *arg.

WARNING: Documentation/ABI/testing/sysfs-class-reboot-mode-reboot_modes:36: abi_sys_class_reboot_mode_driver_reboot_modes doesn't have a description
Documentation/ABI/testing/sysfs-class-reboot-mode-reboot_modes:1: ERROR: Unexpected indentation. [docutils]
Documentation/ABI/testing/sysfs-class-reboot-mode-reboot_modes:1: ERROR: Unexpected indentation. [docutils]
Documentation/ABI/testing/sysfs-class-reboot-mode-reboot_modes:1: WARNING: Inline emphasis start-string without end-string. [docutils]
Documentation/ABI/testing/sysfs-class-reboot-mode-reboot_modes:1: ERROR: Unexpected indentation. [docutils]

Fixes: d3da03025e6d ("Documentation: ABI: Add sysfs-class-reboot-mode-reboot_modes")
Signed-off-by: Randy Dunlap 
Reviewed-by: Bartosz Golaszewski 
Link: https://patch.msgid.link/20260426232705.422938-1-rdunlap@infradead.org
Signed-off-by: Sebastian Reichel 
Signed-off-by: Sasha Levin

dt-bindings: phy: sc8280xp-qmp-pcie: Disallow bifurcation register on Purwa

2026-07-24T14:20:12+00:00

[ Upstream commit b3ee497970c63cea37976aeaa84bac39611fe0eb ]

Neither of the two Gen4x4 PHYs found on Purwa supports bifurcation.
The PHY is however physically laid out as if it were to, since there
are two separate ports (A/B).

Split out a new if-then block to un-require the bifurcation register
handle to squash this warning:

purwa-iot-evk.dtb: phy@1bd4000 (qcom,x1p42100-qmp-gen4x4-pcie-phy): 'qcom,4ln-config-sel' is a required property

Fixes: 2e1ffd4c1805 ("dt-bindings: phy: qcom,qmp-pcie: Add X1P42100 PCIe Gen4x4 PHY")
Reported-by: Rob Herring 
Closes: https://lore.kernel.org/linux-arm-msm/176857775469.1631885.16133311938753588148.robh@kernel.org/
Signed-off-by: Konrad Dybcio 
Acked-by: Rob Herring (Arm) 
Link: https://patch.msgid.link/20260610-topic-purwa_phy_shutup_warning-v2-1-951c1fbfe9b2@oss.qualcomm.com
Signed-off-by: Vinod Koul 
Signed-off-by: Sasha Levin

dt-bindings: dma: snps,dw-axi-dmac: Add fallback compatible for CV1800B

2026-07-24T14:20:12+00:00

[ Upstream commit 7524fe142b5a772f8421aeee2132cf7e21a00103 ]

The previous version of the binding change only add compatible
string without adding the fallback compatible, this breaks
backward compatibility. Add the needed fallback compatible to
fix this.

Fixes: be3e2a0419c6 ("dt-bindings: dma: snps,dw-axi-dmac: Add CV1800B compatible")
Signed-off-by: Inochi Amaoto 
Acked-by: Conor Dooley 
Link: https://patch.msgid.link/20260511063818.463877-2-inochiama@gmail.com
Signed-off-by: Vinod Koul 
Signed-off-by: Sasha Levin

docs: memfd_preservation: fix rendering of ABI documentation

2026-07-24T14:20:07+00:00

[ Upstream commit 3a358c78093f98a70d84c934b7054f636bc846f2 ]

The "memfd Live Update ABI" section in include/linux/kho/abi/memfd.h
currently does not render in the exported documentation. This is because
it should not include the "DOC:" in its reference. Drop it to ensure
correct rendering. Tested by running make htmldocs.

Fixes: 15fc11bb2cb6 ("docs: add documentation for memfd preservation via LUO")
Signed-off-by: Pratyush Yadav (Google) 
Tested-by: Randy Dunlap 
Acked-by: Randy Dunlap 
Link: https://patch.msgid.link/20260605160645.3650271-1-pratyush@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) 
Signed-off-by: Sasha Levin

dt-bindings: clock: qcom: Add X1P42100 camera clock controller

2026-07-24T14:20:06+00:00

[ Upstream commit 97a5e120be5d3d7cf7d221b8703921046b73f0d2 ]

Add X1P42100 camera clock controller support and clock bindings
for camera QDSS debug clocks which are applicable for both X1E80100
and X1P42100 platforms.

Reviewed-by: Krzysztof Kozlowski 
Signed-off-by: Jagadeesh Kona 
Link: https://lore.kernel.org/r/20260507-purwa-videocc-camcc-v5-2-fc3af4130282@oss.qualcomm.com
Signed-off-by: Bjorn Andersson 
Stable-dep-of: 1e6ae74ac6f2 ("clk: qcom: camcc-x1e80100: Add support for camera QDSS debug clocks")
Signed-off-by: Sasha Levin

dt-bindings: dma: nvidia,tegra186-gpc-dma: Make reset optional

2026-07-24T14:20:04+00:00

[ Upstream commit cc6049bd3fa8501ee27042df469a19ed69cf406d ]

On Tegra264, GPCDMA reset control is not exposed to Linux and is handled
by the boot firmware.

Although reset was not exposed in Tegra234 as well, the firmware supported
a dummy reset which just returns success on reset without doing an actual
reset. This is also not supported in Tegra264 BPMP. Therefore mark 'reset'
and 'reset-names' properties as required only for devices prior to
Tegra264.

This also necessitates that the Tegra264 compatible be standalone and
cannot have the fallback compatible of Tegra186. Since there is no
functional impact, we keep reset as required for Tegra234 to avoid
breaking the ABI.

Fixes: bb8c97571db5 ("dt-bindings: dma: Add Tegra264 compatible string")
Signed-off-by: Akhil R 
Acked-by: Rob Herring (Arm) 
Acked-by: Thierry Reding 
Reviewed-by: Jon Hunter 
Link: https://patch.msgid.link/20260331102303.33181-2-akhilrajeev@nvidia.com
Signed-off-by: Vinod Koul 
Signed-off-by: Sasha Levin