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
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KVM/arm64 fixes for 7.0, take #1
- Make sure we don't leak any S1POE state from guest to guest when
the feature is supported on the HW, but not enabled on the host
- Propagate the ID registers from the host into non-protected VMs
managed by pKVM, ensuring that the guest sees the intended feature set
- Drop double kern_hyp_va() from unpin_host_sve_state(), which could
bite us if we were to change kern_hyp_va() to not being idempotent
- Don't leak stage-2 mappings in protected mode
- Correctly align the faulting address when dealing with single page
stage-2 mappings for PAGE_SIZE > 4kB
- Fix detection of virtualisation-capable GICv5 IRS, due to the
maintainer being obviously fat fingered...
- Remove duplication of code retrieving the ASID for the purpose of
S1 PT handling
- Fix slightly abusive const-ification in vgic_set_kvm_info()
KVM_CAP_SYNC_MMU is provided by KVM's MMU notifiers, which are now always
available. Move the definition from individual architectures to common
code.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
We currently have three versions of the ASID retrieval code, one
in the S1 walker, and two in the VNCR handling (although the last
two are limited to the EL2&0 translation regime).
Make this code common, and take this opportunity to also simplify
the code a bit while switching over to the TTBRx_EL1_ASID macro.
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20260225104718.14209-1-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
All architectures now use MMU notifier for KVM page table management.
Remove the Kconfig symbol and the code that is used when it is
disabled.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
It appears that a !! became ! during a cleanup, resulting in inverted
logic when detecting if a host GICv5 implementation is capable of
virtualization.
Re-add the missing !, fixing the behaviour.
Fixes: 3227c3a89d65f ("irqchip/gic-v5: Check if impl is virt capable")
Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
Link: https://patch.msgid.link/20260225083130.3378490-1-sascha.bischoff@arm.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
Commit 0c4762e26879 ("KVM: arm64: nv: Avoid NV stage-2 code when NV is
not supported") added an early return to several functions in
arch/arm64/kvm/nested.c to prevent a UBSAN shift-out-of-bounds error
when accessing the pgt union for non-nested VMs.
However, this early return was inadvertently applied to
kvm_arch_flush_shadow_all() as well, causing it to skip the call to
kvm_uninit_stage2_mmu(kvm) for all non-nested VMs.
For pKVM, skipping this teardown means the host never unshares the
guest's memory with the EL2 hypervisor. When the host kernel later
recycles these leaked pages for a new VM, it attempts to re-share them.
The hypervisor correctly rejects this with -EPERM, triggering a host
WARN_ON and hanging the guest.
Fix this by dropping the early return from kvm_arch_flush_shadow_all().
The for-loop guarding the nested MMU cleanup already bounds itself when
nested_mmus_size == 0, allowing execution to proceed to
kvm_uninit_stage2_mmu() as intended.
Reported-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/all/60916cb6-f460-4751-b910-f63c58700ad0@sirena.org.uk/
Fixes: 0c4762e26879 ("KVM: arm64: nv: Avoid NV stage-2 code when NV is not supported")
Signed-off-by: Fuad Tabba <tabba@google.com>
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://patch.msgid.link/20260222083352.89503-1-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
Pull fsverity fixes from Eric Biggers:
- Fix a build error on parisc
- Remove the non-large-folio-aware function fsverity_verify_page()
* tag 'fsverity-for-linus' of git://git.kernel.org/pub/scm/fs/fsverity/linux:
fsverity: fix build error by adding fsverity_readahead() stub
fsverity: remove fsverity_verify_page()
f2fs: make f2fs_verify_cluster() partially large-folio-aware
f2fs: remove unnecessary ClearPageUptodate in f2fs_verify_cluster()
Since 3669ddd8fa8b5 ("KVM: arm64: Add a range to pkvm_mappings"),
pKVM tracks the memory that has been mapped into a guest in a
side data structure. Crucially, it uses it to find out whether
a page has already been mapped, and therefore refuses to map it
twice. So far, so good.
However, this very patch completely breaks non-4kB page support,
with guests being unable to boot. The most obvious symptom is that
we take the same fault repeatedly, and not making forward progress.
A quick investigation shows that this is because of the above
rejection code.
As it turns out, there are multiple issues at play:
- while the HPFAR_EL2 register gives you the faulting IPA minus
the bottom 12 bits, it will still give you the extra bits that
are part of the page offset for anything larger than 4kB,
even for a level-3 mapping
- pkvm_pgtable_stage2_map() assumes that the address passed as
a parameter is aligned to the size of the intended mapping
- the faulting address is only aligned for a non-page mapping
When the planets are suitably aligned (pun intended), the guest
faults on a page by accessing it past the bottom 4kB, and extra bits
get set in the HPFAR_EL2 register. If this results in a page mapping
(which is likely with large granule sizes), nothing aligns it further
down, and pkvm_mapping_iter_first() finds an intersection that
doesn't really exist. We assume this is a spurious fault and return
-EAGAIN. And again...
This doesn't hit outside of the protected code, as the page table
code always aligns the IPA down to a page boundary, hiding the issue
for everyone else.
Fix it by always forcing the alignment on vma_pagesize, irrespective
of the value of vma_pagesize.
Fixes: 3669ddd8fa8b5 ("KVM: arm64: Add a range to pkvm_mappings")
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://https://patch.msgid.link/20260222141000.3084258-1-maz@kernel.org
Cc: stable@vger.kernel.org
Pull crypto library fix from Eric Biggers:
"Fix a big endian specific issue in the PPC64-optimized AES code"
* tag 'libcrypto-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux:
lib/crypto: powerpc/aes: Fix rndkey_from_vsx() on big endian CPUs
hppa-linux-gcc 9.5.0 generates a call to fsverity_readahead() in
f2fs_readahead() when CONFIG_FS_VERITY=n, because it fails to do the
expected dead code elimination based on vi always being NULL. Fix the
build error by adding an inline stub for fsverity_readahead(). Since
it's just for opportunistic readahead, just make it a no-op.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202602180838.pwICdY2r-lkp@intel.com/
Fixes: 45dcb3ac9832 ("f2fs: consolidate fsverity_info lookup")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20260218012244.18536-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
In preparation for making the kmalloc family of allocators type aware,
we need to make sure that the returned type from the allocation matches
the type of the variable being assigned. (Before, the allocator would
always return "void *", which can be implicitly cast to any pointer type.)
The assigned type is "struct gic_kvm_info", but the returned type,
while matching, is const qualified. To get them exactly matching, just
use the dereferenced pointer for the sizeof().
Signed-off-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/20260206223022.it.052-kees@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
Stephen retired and stepped back from -next maintainership, update his
entry in CREDITS to recognise his 18 years of hard work making it what
it is today and all the impact it's had on our development process.
Also update to his current GnuPG key while we're here.
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I finally got a big endian PPC64 kernel to boot in QEMU. The PPC64 VSX
optimized AES library code does work in that case, with the exception of
rndkey_from_vsx() which doesn't take into account that the order in
which the VSX code stores the round key words depends on the endianness.
So fix rndkey_from_vsx() to do the right thing on big endian CPUs.
Fixes: 7cf2082e74ce ("lib/crypto: powerpc/aes: Migrate POWER8 optimized code into library")
Link: https://lore.kernel.org/r/20260216022104.332991-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Now that fsverity_verify_page() has no callers, remove it.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20260218010630.7407-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
The `sve_state` pointer in `hyp_vcpu->vcpu.arch` is initialized as a
hypervisor virtual address during vCPU initialization in
`pkvm_vcpu_init_sve()`.
`unpin_host_sve_state()` calls `kern_hyp_va()` on this address. Since
`kern_hyp_va()` is idempotent, it's not a bug. However, it is
unnecessary and potentially confusing. Remove the redundant conversion.
Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260213143815.1732675-5-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>