Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst
Clone this repository
For self-hosted knots, clone URLs may differ based on your setup.
Download tar.gz
* arm64/for-next/perf:
: Perf updates
perf/arm-cmn: Fix resource_size_t printk specifier in arm_cmn_init_dtc()
perf/arm-cmn: Fix incorrect error check for devm_ioremap()
perf: add NVIDIA Tegra410 C2C PMU
perf: add NVIDIA Tegra410 CPU Memory Latency PMU
perf/arm_cspmu: nvidia: Add Tegra410 PCIE-TGT PMU
perf/arm_cspmu: nvidia: Add Tegra410 PCIE PMU
perf/arm_cspmu: Add arm_cspmu_acpi_dev_get
perf/arm_cspmu: nvidia: Add Tegra410 UCF PMU
perf/arm_cspmu: nvidia: Rename doc to Tegra241
perf/arm-cmn: Stop claiming entire iomem region
arm64: cpufeature: Use pmuv3_implemented() function
arm64: cpufeature: Make PMUVer and PerfMon unsigned
KVM: arm64: Read PMUVer as unsigned
* arm64/for-next/read-once:
: Fixes for __READ_ONCE() with CONFIG_LTO=y
arm64, compiler-context-analysis: Permit alias analysis through __READ_ONCE() with CONFIG_LTO=y
arm64: Optimize __READ_ONCE() with CONFIG_LTO=y
* for-next/misc:
: Miscellaneous cleanups/fixes
arm64: rsi: use linear-map alias for realm config buffer
arm64: Kconfig: fix duplicate word in CMDLINE help text
arm64: mte: Skip TFSR_EL1 checks and barriers in synchronous tag check mode
arm64/hwcap: Generate the KERNEL_HWCAP_ definitions for the hwcaps
arm64: kexec: Remove duplicate allocation for trans_pgd
arm64: mm: Use generic enum pgtable_level
arm64: scs: Remove redundant save/restore of SCS SP on entry to/from EL0
arm64: remove ARCH_INLINE_*
* for-next/tlbflush:
: Refactor the arm64 TLB invalidation API and implementation
arm64: mm: __ptep_set_access_flags must hint correct TTL
arm64: mm: Provide level hint for flush_tlb_page()
arm64: mm: Wrap flush_tlb_page() around __do_flush_tlb_range()
arm64: mm: More flags for __flush_tlb_range()
arm64: mm: Refactor __flush_tlb_range() to take flags
arm64: mm: Refactor flush_tlb_page() to use __tlbi_level_asid()
arm64: mm: Simplify __flush_tlb_range_limit_excess()
arm64: mm: Simplify __TLBI_RANGE_NUM() macro
arm64: mm: Re-implement the __flush_tlb_range_op macro in C
arm64: mm: Inline __TLBI_VADDR_RANGE() into __tlbi_range()
arm64: mm: Push __TLBI_VADDR() into __tlbi_level()
arm64: mm: Implicitly invalidate user ASID based on TLBI operation
arm64: mm: Introduce a C wrapper for by-range TLB invalidation
arm64: mm: Re-implement the __tlbi_level macro as a C function
* for-next/ttbr-macros-cleanup:
: Cleanups of the TTBR1_* macros
arm64/mm: Directly use TTBRx_EL1_CnP
arm64/mm: Directly use TTBRx_EL1_ASID_MASK
arm64/mm: Describe TTBR1_BADDR_4852_OFFSET
* for-next/kselftest:
: arm64 kselftest updates
selftests/arm64: Implement cmpbr_sigill() to hwcap test
* for-next/feat_lsui:
: Futex support using FEAT_LSUI instructions to avoid toggling PAN
arm64: armv8_deprecated: Disable swp emulation when FEAT_LSUI present
arm64: Kconfig: Add support for LSUI
KVM: arm64: Use CAST instruction for swapping guest descriptor
arm64: futex: Support futex with FEAT_LSUI
arm64: futex: Refactor futex atomic operation
KVM: arm64: kselftest: set_id_regs: Add test for FEAT_LSUI
KVM: arm64: Expose FEAT_LSUI to guests
arm64: cpufeature: Add FEAT_LSUI
* for-next/mpam: (40 commits)
: Expose MPAM to user-space via resctrl:
: - Add architecture context-switch and hiding of the feature from KVM.
: - Add interface to allow MPAM to be exposed to user-space using resctrl.
: - Add errata workaoround for some existing platforms.
: - Add documentation for using MPAM and what shape of platforms can use resctrl
arm64: mpam: Add initial MPAM documentation
arm_mpam: Quirk CMN-650's CSU NRDY behaviour
arm_mpam: Add workaround for T241-MPAM-6
arm_mpam: Add workaround for T241-MPAM-4
arm_mpam: Add workaround for T241-MPAM-1
arm_mpam: Add quirk framework
arm_mpam: resctrl: Call resctrl_init() on platforms that can support resctrl
arm64: mpam: Select ARCH_HAS_CPU_RESCTRL
arm_mpam: resctrl: Add empty definitions for assorted resctrl functions
arm_mpam: resctrl: Update the rmid reallocation limit
arm_mpam: resctrl: Add resctrl_arch_rmid_read()
arm_mpam: resctrl: Allow resctrl to allocate monitors
arm_mpam: resctrl: Add support for csu counters
arm_mpam: resctrl: Add monitor initialisation and domain boilerplate
arm_mpam: resctrl: Add kunit test for control format conversions
arm_mpam: resctrl: Add support for 'MB' resource
arm_mpam: resctrl: Wait for cacheinfo to be ready
arm_mpam: resctrl: Add rmid index helpers
arm_mpam: resctrl: Convert to/from MPAMs fixed-point formats
arm_mpam: resctrl: Hide CDP emulation behind CONFIG_EXPERT
...
* for-next/hotplug-batched-tlbi:
: arm64/mm: Enable batched TLB flush in unmap_hotplug_range()
arm64/mm: Reject memory removal that splits a kernel leaf mapping
arm64/mm: Enable batched TLB flush in unmap_hotplug_range()
* for-next/bbml2-fixes:
: Fixes for realm guest and BBML2_NOABORT
arm64: mm: Remove pmd_sect() and pud_sect()
arm64: mm: Handle invalid large leaf mappings correctly
arm64: mm: Fix rodata=full block mapping support for realm guests
* for-next/sysreg:
: arm64 sysreg updates
arm64/sysreg: Update ID_AA64SMFR0_EL1 description to DDI0601 2025-12
arm64/sysreg: Update ID_AA64ZFR0_EL1 description to DDI0601 2025-12
arm64/sysreg: Update ID_AA64FPFR0_EL1 description to DDI0601 2025-12
arm64/sysreg: Update ID_AA64ISAR2_EL1 description to DDI0601 2025-12
arm64/sysreg: Update ID_AA64ISAR0_EL1 description to DDI0601 2025-12
arm64/sysreg: Update SMIDR_EL1 to DDI0601 2025-06
* for-next/generic-entry:
: More arm64 refactoring towards using the generic entry code
arm64: Check DAIF (and PMR) at task-switch time
arm64: entry: Use split preemption logic
arm64: entry: Use irqentry_{enter_from,exit_to}_kernel_mode()
arm64: entry: Consistently prefix arm64-specific wrappers
arm64: entry: Don't preempt with SError or Debug masked
entry: Split preemption from irqentry_exit_to_kernel_mode()
entry: Split kernel mode logic from irqentry_{enter,exit}()
entry: Move irqentry_enter() prototype later
entry: Remove local_irq_{enable,disable}_exit_to_user()
entry: Fix stale comment for irqentry_enter()
* for-next/acpi:
: arm64 ACPI updates
ACPI: AGDI: fix missing newline in error message
When building for 32-bit ARM, there is a warning when using the %llx
specifier to print a resource_size_t variable:
drivers/perf/arm-cmn.c: In function 'arm_cmn_init_dtc':
drivers/perf/arm-cmn.c:2149:73: error: format '%llx' expects argument of type 'long long unsigned int', but argument 4 has type 'resource_size_t' {aka 'unsigned int'} [-Werror=format=]
2149 | "Failed to request DTC region 0x%llx\n", base);
| ~~~^ ~~~~
| | |
| | resource_size_t {aka unsigned int}
| long long unsigned int
| %x
Use the %pa specifier to handle the possible sizes of phys_addr_t
properly. This requires passing the variable by reference.
Fixes: 5394396ff548 ("perf/arm-cmn: Stop claiming entire iomem region")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Robin murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
When enabling Clang's Context Analysis (aka. Thread Safety Analysis) on
kernel/futex/core.o (see Peter's changes at [1]), in arm64 LTO builds we
could see:
| kernel/futex/core.c:982:1: warning: spinlock 'atomic ? __u.__val : q->lock_ptr' is still held at the end of function [-Wthread-safety-analysis]
| 982 | }
| | ^
| kernel/futex/core.c:976:2: note: spinlock acquired here
| 976 | spin_lock(lock_ptr);
| | ^
| kernel/futex/core.c:982:1: warning: expecting spinlock 'q->lock_ptr' to be held at the end of function [-Wthread-safety-analysis]
| 982 | }
| | ^
| kernel/futex/core.c:966:6: note: spinlock acquired here
| 966 | void futex_q_lockptr_lock(struct futex_q *q)
| | ^
| 2 warnings generated.
Where we have:
extern void futex_q_lockptr_lock(struct futex_q *q) __acquires(q->lock_ptr);
..
void futex_q_lockptr_lock(struct futex_q *q)
{
spinlock_t *lock_ptr;
/*
* See futex_unqueue() why lock_ptr can change.
*/
guard(rcu)();
retry:
>> lock_ptr = READ_ONCE(q->lock_ptr);
spin_lock(lock_ptr);
...
}
At the time of the above report (prior to removal of the 'atomic' flag),
Clang Thread Safety Analysis's alias analysis resolved 'lock_ptr' to
'atomic ? __u.__val : q->lock_ptr' (now just '__u.__val'), and used
this as the identity of the context lock given it cannot "see through"
the inline assembly; however, we want 'q->lock_ptr' as the canonical
context lock.
While for code generation the compiler simplified to '__u.__val' for
pointers (8 byte case -> 'atomic' was set), TSA's analysis (a) happens
much earlier on the AST, and (b) would be the wrong deduction.
Now that we've gotten rid of the 'atomic' ternary comparison, we can
return '__u.__val' through a pointer that we initialize with '&x', but
then update via a pointer-to-pointer. When READ_ONCE()'ing a context
lock pointer, TSA's alias analysis does not invalidate the initial alias
when updated through the pointer-to-pointer, and we make it effectively
"see through" the __READ_ONCE().
Code generation is unchanged.
Link: https://lkml.kernel.org/r/20260121110704.221498346@infradead.org [1]
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202601221040.TeM0ihff-lkp@intel.com/
Cc: Peter Zijlstra <peterz@infradead.org>
Tested-by: Boqun Feng <boqun@kernel.org>
Reviewed-by: David Laight <david.laight.linux@gmail.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
rsi_get_realm_config() passes its argument to virt_to_phys(), but
&config is a kernel image address and not a linear-map alias.
On arm64 this triggers the below warning:
virt_to_phys used for non-linear address: (____ptrval____) (config+0x0/0x1000)
WARNING: arch/arm64/mm/physaddr.c:15 at __virt_to_phys+0x50/0x70, CPU#0: swapper/0
Modules linked in:
.....
Hardware name: linux,dummy-virt (DT)
pstate: 200000c5 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __virt_to_phys+0x50/0x70
lr : __virt_to_phys+0x4c/0x70
.....
......
Call trace:
__virt_to_phys+0x50/0x70 (P)
arm64_rsi_init+0xa0/0x1b8
setup_arch+0x13c/0x1a0
start_kernel+0x68/0x398
__primary_switched+0x88/0x90
Pass lm_alias(&config) instead so the RSI call uses the linear-map
alias of the same buffer and avoids the boot-time warning.
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
It has been reported that since commit 752a0d1d483e9 ("arm64: mm:
Provide level hint for flush_tlb_page()"), the arm64
check_hugetlb_options selftest has been locking up while running "Check
child hugetlb memory with private mapping, sync error mode and mmap
memory".
This is due to hugetlb (and THP) helpers casting their PMD/PUD entries
to PTE and calling __ptep_set_access_flags(), which issues a
__flush_tlb_page(). Now that this is hinted for level 3, in this case,
the TLB entry does not get evicted and we end up in a spurious fault
loop.
Fix this by creating a __ptep_set_access_flags_anysz() function which
takes the pgsize of the entry. It can then add the appropriate hint. The
"_anysz" approach is the established pattern for problems of this class.
Reported-by: Aishwarya TCV <Aishwarya.TCV@arm.com>
Fixes: 752a0d1d483e ("arm64: mm: Provide level hint for flush_tlb_page()")
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Replace all TTBR_CNP_BIT macro instances with TTBRx_EL1_CNP_BIT which
is a standard field from tools sysreg format. Drop the now redundant
custom macro TTBR_CNP_BIT. No functional change.
Cc: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oupton@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: kvmarm@lists.linux.dev
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
The function executes a CBEQ instruction which is valid if the CPU
supports the CMPBR extension. The CBEQ branches to skip the following
UDF instruction, and no SIGILL is generated. Otherwise, it will
generate a SIGILL.
Signed-off-by: Yifan Wu <wuyifan50@huawei.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
The purpose of supporting LSUI is to eliminate PAN toggling. CPUs that
support LSUI are unlikely to support a 32-bit runtime. Rather than
emulating the SWP instruction using LSUI instructions in order to remove
PAN toggling, simply disable SWP emulation.
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
[catalin.marinas@arm.com: some tweaks to the in-code comment]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
MPAM (Memory Partitioning and Monitoring) is now exposed to user-space via
resctrl. Add some documentation so the user knows what features to expect.
Reviewed-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Tested-by: Gavin Shan <gshan@redhat.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Jesse Chick <jessechick@os.amperecomputing.com>
Signed-off-by: James Morse <james.morse@arm.com>
Linear and vmemmap mappings that get torn down during a memory hot remove
operation might contain leaf level entries on any page table level. If the
requested memory range's linear or vmemmap mappings falls within such leaf
entries, new mappings need to be created for the remaining memory mapped on
the leaf entry earlier, following standard break before make aka BBM rules.
But kernel cannot tolerate BBM and hence remapping to fine grained leaves
would not be possible on systems without BBML2_NOABORT.
Currently memory hot remove operation does not perform such restructuring,
and so removing memory ranges that could split a kernel leaf level mapping
need to be rejected.
While memory_hotplug.c does appear to permit hot removing arbitrary ranges
of memory, the higher layers that drive memory_hotplug (e.g. ACPI, virtio,
...) all appear to treat memory as fixed size devices. So it is impossible
to hot unplug a different amount than was previously hot plugged, and hence
we should never see a rejection in practice, but adding the check makes us
robust against a future change.
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Link: https://lore.kernel.org/all/aWZYXhrT6D2M-7-N@willie-the-truck/
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Suggested-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
The semantics of pXd_leaf() are very similar to pXd_sect(). The only
difference is that pXd_sect() only considers it a section if PTE_VALID
is set, whereas pXd_leaf() permits both "valid" and "present-invalid"
types.
Using pXd_sect() has caused issues now that large leaf entries can be
present-invalid since commit a166563e7ec37 ("arm64: mm: support large
block mapping when rodata=full"), so let's just remove the API and
standardize on pXd_leaf().
There are a few callsites of the form pXd_leaf(READ_ONCE(*pXdp)). This
was previously fine for the pXd_sect() macro because it only evaluated
its argument once. But pXd_leaf() evaluates its argument multiple times.
So let's avoid unintended side effects by reimplementing pXd_leaf() as
an inline function.
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
The 2025 extensions add FEAT_SME2P3, including LUT6.
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
When __switch_to() switches from a 'prev' task to a 'next' task, various
pieces of CPU state are expected to have specific values, such that
these do not need to be saved/restored. If any of these hold an
unexpected value when switching away from the prev task, they could lead
to surprising behaviour in the context of the next task, and it would be
difficult to determine where they were configured to their unexpected
value.
Add some checks for DAIF and PMR at task-switch time so that we can
detect such issues.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Jinjie Ruan <ruanjinjie@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Add the missing trailing newline to the dev_err() message
printed when SDEI event registration fails.
This keeps the error output as a properly terminated log line.
Fixes: a2a591fb76e6 ("ACPI: AGDI: Add driver for Arm Generic Diagnostic Dump and Reset device")
Reviewed-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Signed-off-by: Haoyu Lu <hechushiguitu666@gmail.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Check devm_ioremap() return value for NULL instead of ERR_PTR and return
-ENOMEM on failure. devm_ioremap() never returns ERR_PTR, using IS_ERR()
skips the error path and may cause a NULL pointer dereference.
Fixes: 5394396ff548 ("perf/arm-cmn: Stop claiming entire iomem region")
Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Signed-off-by: Will Deacon <will@kernel.org>
Rework arm64 LTO __READ_ONCE() to improve code generation as follows:
1. Replace _Generic-based __unqual_scalar_typeof() with more complete
__rwonce_typeof_unqual(). This strips qualifiers from all types, not
just integer types, which is required to be able to assign (must be
non-const) to __u.__val in the non-atomic case (required for #2).
One subtle point here is that non-integer types of __val could be const
or volatile within the union with the old __unqual_scalar_typeof(), if
the passed variable is const or volatile. This would then result in a
forced load from the stack if __u.__val is volatile; in the case of
const, it does look odd if the underlying storage changes, but the
compiler is told said member is "const" -- it smells like UB.
2. Eliminate the atomic flag and ternary conditional expression. Move
the fallback volatile load into the default case of the switch,
ensuring __u is unconditionally initialized across all paths.
The statement expression now unconditionally returns __u.__val.
This refactoring appears to help the compiler improve (or fix) code
generation.
With a defconfig + LTO + debug options builds, we observe different
codegen for the following functions:
btrfs_reclaim_sweep (708 -> 1032 bytes)
btrfs_sinfo_bg_reclaim_threshold_store (200 -> 204 bytes)
check_mem_access (3652 -> 3692 bytes) [inlined bpf_map_is_rdonly]
console_flush_all (1268 -> 1264 bytes)
console_lock_spinning_disable_and_check (180 -> 176 bytes)
igb_add_filter (640 -> 636 bytes)
igb_config_tx_modes (2404 -> 2400 bytes)
kvm_vcpu_on_spin (480 -> 476 bytes)
map_freeze (376 -> 380 bytes)
netlink_bind (1664 -> 1656 bytes)
nmi_cpu_backtrace (404 -> 400 bytes)
set_rps_cpu (516 -> 520 bytes)
swap_cluster_readahead (944 -> 932 bytes)
tcp_accecn_third_ack (328 -> 336 bytes)
tcp_create_openreq_child (1764 -> 1772 bytes)
tcp_data_queue (5784 -> 5892 bytes)
tcp_ecn_rcv_synack (620 -> 628 bytes)
xen_manage_runstate_time (944 -> 896 bytes)
xen_steal_clock (340 -> 296 bytes)
Increase of some functions are due to more aggressive inlining due to
better codegen (in this build, e.g. bpf_map_is_rdonly is no longer
present due to being inlined completely).
NOTE: The return-value-of-function-drops-qualifiers hack was first
suggested by Al Viro in [1], which notes some of its limitations which
make it unsuitable for a general __unqual_scalar_typeof() replacement.
Notably, array types are not supported, and GCC 8.1-8.3 still fail. Why
should we use it here? READ_ONCE() does not support reading whole
arrays, and the GCC version problem only affects 3 minor releases of a
very ancient still-supported GCC version; not only that, this arm64
READ_ONCE() version is currently only activated by LTO builds, which
to-date are *only supported by Clang*!
Link: https://lore.kernel.org/all/20260111182010.GH3634291@ZenIV/ [1]
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Will Deacon <will@kernel.org>