- Correctly handle deeactivation of interrupts that were activated from
LRs. Since EOIcount only denotes deactivation of interrupts that
are not present in an LR, start EOIcount deactivation walk *after*
the last irq that made it into an LR.
- Avoid calling into the stubs to probe for ICH_VTR_EL2.TDS when
pKVM is already enabled -- not only thhis isn't possible (pKVM
will reject the call), but it is also useless: this can only
happen for a CPU that has already booted once, and the capability
will not change.
- Fix a couple of low-severity bugs in our S2 fault handling path,
affecting the recently introduced LS64 handling and the even more
esoteric handling of hwpoison in a nested context
- Address yet another syzkaller finding in the vgic initialisation,
where we would end-up destroying an uninitialised vgic with nasty
consequences
- Address an annoying case of pKVM failing to boot when some of the
memblock regions that the host is faulting in are not page-aligned
- Inject some sanity in the NV stage-2 walker by checking the limits
against the advertised PA size, and correctly report the resulting
faults
PPC:
- Fix a PPC e500 build error due to a long-standing wart that was exposed by
the recent conversion to kmalloc_obj(); rip out all the ugliness that
led to the wart.
RISC-V:
- Prevent speculative out-of-bounds access using array_index_nospec()
in APLIC interrupt handling, ONE_REG regiser access, AIA CSR access,
float register access, and PMU counter access
- Fix potential use-after-free issues in kvm_riscv_gstage_get_leaf(),
kvm_riscv_aia_aplic_has_attr(), and kvm_riscv_aia_imsic_has_attr()
- Fix potential null pointer dereference in kvm_riscv_vcpu_aia_rmw_topei()
- Fix off-by-one array access in SBI PMU
- Skip THP support check during dirty logging
- Fix error code returned for Smstateen and Ssaia ONE_REG interface
- Check host Ssaia extension when creating AIA irqchip
x86:
- Fix cases where CPUID mitigation features were incorrectly marked as
available whenever the kernel used scattered feature words for them.
- Validate _all_ GVAs, rather than just the first GVA, when processing
a range of GVAs for Hyper-V's TLB flush hypercalls.
- Fix a brown paper bug in add_atomic_switch_msr().
- Use hlist_for_each_entry_srcu() when traversing mask_notifier_list,
to fix a lockdep warning; KVM doesn't hold RCU, just irq_srcu.
- Ensure AVIC VMCB fields are initialized if the VM has an in-kernel local
APIC (and AVIC is enabled at the module level).
- Update CR8 write interception when AVIC is (de)activated, to fix a bug
where the guest can run in perpetuity with the CR8 intercept enabled.
- Add a quirk to skip the consistency check on FREEZE_IN_SMM, i.e. to allow
L1 hypervisors to set FREEZE_IN_SMM. This reverts (by default) an
unintentional tightening of userspace ABI in 6.17, and provides some
amount of backwards compatibility with hypervisors who want to freeze
PMCs on VM-Entry.
- Validate the VMCS/VMCB on return to a nested guest from SMM, because
either userspace or the guest could stash invalid values in memory
and trigger the processor's consistency checks.
Generic:
- Remove a subtle pseudo-overlay of kvm_stats_desc, which, aside from being
unnecessary and confusing, triggered compiler warnings due to
-Wflex-array-member-not-at-end.
- Document that vcpu->mutex is take outside of kvm->slots_lock and
kvm->slots_arch_lock, which is intentional and desirable despite being
rather unintuitive.
Selftests:
- Increase the maximum number of NUMA nodes in the guest_memfd selftest to
64 (from 8).
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm fixes from Paolo Bonzini:
"Quite a large pull request, partly due to skipping last week and
therefore having material from ~all submaintainers in this one. About
a fourth of it is a new selftest, and a couple more changes are large
in number of files touched (fixing a -Wflex-array-member-not-at-end
compiler warning) or lines changed (reformatting of a table in the API
documentation, thanks rST).
But who am I kidding---it's a lot of commits and there are a lot of
bugs being fixed here, some of them on the nastier side like the
RISC-V ones.
ARM:
- Correctly handle deactivation of interrupts that were activated
from LRs. Since EOIcount only denotes deactivation of interrupts
that are not present in an LR, start EOIcount deactivation walk
*after* the last irq that made it into an LR
- Avoid calling into the stubs to probe for ICH_VTR_EL2.TDS when pKVM
is already enabled -- not only thhis isn't possible (pKVM will
reject the call), but it is also useless: this can only happen for
a CPU that has already booted once, and the capability will not
change
- Fix a couple of low-severity bugs in our S2 fault handling path,
affecting the recently introduced LS64 handling and the even more
esoteric handling of hwpoison in a nested context
- Address yet another syzkaller finding in the vgic initialisation,
where we would end-up destroying an uninitialised vgic with nasty
consequences
- Address an annoying case of pKVM failing to boot when some of the
memblock regions that the host is faulting in are not page-aligned
- Inject some sanity in the NV stage-2 walker by checking the limits
against the advertised PA size, and correctly report the resulting
faults
PPC:
- Fix a PPC e500 build error due to a long-standing wart that was
exposed by the recent conversion to kmalloc_obj(); rip out all the
ugliness that led to the wart
RISC-V:
- Prevent speculative out-of-bounds access using array_index_nospec()
in APLIC interrupt handling, ONE_REG regiser access, AIA CSR
access, float register access, and PMU counter access
- Fix potential use-after-free issues in kvm_riscv_gstage_get_leaf(),
kvm_riscv_aia_aplic_has_attr(), and kvm_riscv_aia_imsic_has_attr()
- Fix potential null pointer dereference in
kvm_riscv_vcpu_aia_rmw_topei()
- Fix off-by-one array access in SBI PMU
- Skip THP support check during dirty logging
- Fix error code returned for Smstateen and Ssaia ONE_REG interface
- Check host Ssaia extension when creating AIA irqchip
x86:
- Fix cases where CPUID mitigation features were incorrectly marked
as available whenever the kernel used scattered feature words for
them
- Validate _all_ GVAs, rather than just the first GVA, when
processing a range of GVAs for Hyper-V's TLB flush hypercalls
- Fix a brown paper bug in add_atomic_switch_msr()
- Use hlist_for_each_entry_srcu() when traversing mask_notifier_list,
to fix a lockdep warning; KVM doesn't hold RCU, just irq_srcu
- Ensure AVIC VMCB fields are initialized if the VM has an in-kernel
local APIC (and AVIC is enabled at the module level)
- Update CR8 write interception when AVIC is (de)activated, to fix a
bug where the guest can run in perpetuity with the CR8 intercept
enabled
- Add a quirk to skip the consistency check on FREEZE_IN_SMM, i.e. to
allow L1 hypervisors to set FREEZE_IN_SMM. This reverts (by
default) an unintentional tightening of userspace ABI in 6.17, and
provides some amount of backwards compatibility with hypervisors
who want to freeze PMCs on VM-Entry
- Validate the VMCS/VMCB on return to a nested guest from SMM,
because either userspace or the guest could stash invalid values in
memory and trigger the processor's consistency checks
Generic:
- Remove a subtle pseudo-overlay of kvm_stats_desc, which, aside from
being unnecessary and confusing, triggered compiler warnings due to
-Wflex-array-member-not-at-end
- Document that vcpu->mutex is take outside of kvm->slots_lock and
kvm->slots_arch_lock, which is intentional and desirable despite
being rather unintuitive
Selftests:
- Increase the maximum number of NUMA nodes in the guest_memfd
selftest to 64 (from 8)"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (43 commits)
KVM: selftests: Verify SEV+ guests can read and write EFER, CR0, CR4, and CR8
Documentation: kvm: fix formatting of the quirks table
KVM: x86: clarify leave_smm() return value
selftests: kvm: add a test that VMX validates controls on RSM
selftests: kvm: extract common functionality out of smm_test.c
KVM: SVM: check validity of VMCB controls when returning from SMM
KVM: VMX: check validity of VMCS controls when returning from SMM
KVM: SVM: Set/clear CR8 write interception when AVIC is (de)activated
KVM: SVM: Initialize AVIC VMCB fields if AVIC is enabled with in-kernel APIC
KVM: x86: Introduce KVM_X86_QUIRK_VMCS12_ALLOW_FREEZE_IN_SMM
KVM: x86: Fix SRCU list traversal in kvm_fire_mask_notifiers()
KVM: VMX: Fix a wrong MSR update in add_atomic_switch_msr()
KVM: x86: hyper-v: Validate all GVAs during PV TLB flush
KVM: x86: synthesize CPUID bits only if CPU capability is set
KVM: PPC: e500: Rip out "struct tlbe_ref"
KVM: PPC: e500: Fix build error due to using kmalloc_obj() with wrong type
KVM: selftests: Increase 'maxnode' for guest_memfd tests
KVM: arm64: pkvm: Don't reprobe for ICH_VTR_EL2.TDS on CPU hotplug
KVM: arm64: vgic: Pick EOIcount deactivations from AP-list tail
KVM: arm64: Remove the redundant ISB in __kvm_at_s1e2()
...
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