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Jinu Kim b3e6212dea KVM: x86: Use active memslots for the per-vCPU MMIO cache
KVM tags the per-vCPU MMIO cache with a memslot generation so that a
memslot update invalidates cached MMIO information.  Both the fill and
validation paths use kvm_memslots(), which unconditionally selects address
space 0, even when the vCPU is running in SMM and using address space 1.

Commit 56f17dd3fb ("kvm: x86: fix stale mmio cache bug") added the
memslot generation to the cache key so that a memslot update could not
leave a stale entry valid.  When commit 699023e239 ("KVM: x86: add SMM
to the MMU role, support SMRAM address space") added the SMM address space,
these helpers were not converted to use the active memslots.

Consequently, an update to the SMM memslots can leave an entry from the old
SMM address space apparently valid after the vCPU returns to the normal
address space.  A guest can then cause an access to valid RAM at the same
GFN to be returned to userspace as KVM_EXIT_MMIO.

Completing that exit through the VMM's RAM address space writes the backing
page without going through KVM's write-tracking path.  If the page backs a
nested EPT table, KVM can continue using shadow translations derived from
the old contents.  The WARN_ON_ONCE() in kvm_mmu_write_protect_fault()
catches this invalid cache and memslot combination.

Use the vCPU's active memslots when caching and validating the entry.
Memslot generations are unique across address spaces, so the generation
also distinguishes the normal and SMM views.  This matches the MMIO SPTE
cache, which already uses kvm_vcpu_memslots().

On an unpatched current-mainline kernel, a regression test that fills the
cache in SMM and updates only the SMM memslots fails the intended RAM write
and triggers the kvm_mmu_write_protect_fault() warning.  With this change,
the same test completes the RAM write without a warning.  The x86/smm_test,
set_memory_region_test, and memslot_modification_stress_test selftests also
pass.

Fixes: 699023e239 ("KVM: x86: add SMM to the MMU role, support SMRAM address space")
Cc: stable@vger.kernel.org
Signed-off-by: Jinu Kim <kimjw04271234@gmail.com>
Link: https://patch.msgid.link/20260807112818.958190-1-kimjw04271234@gmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
History 2026-09-30 06:40:49 -07:00
arch KVM: x86: Use active memslots for the per-vCPU MMIO cache 2026-09-30 06:40:49 -07:00
block block: save page offset gaps in cloned bio 2026-09-01 08:42:34 -06:00
certs treewide: fix indentation and whitespace in Kconfig files 2026-05-28 21:24:42 -07:00
crypto This push fixes a memory allocation overrun in crypto acomp. 2026-08-28 09:28:40 -07:00
Documentation Changes since last update: 2026-09-12 08:18:50 -07:00
drivers KVM/arm64 changes for 7.3, take #2 2026-09-21 06:09:47 -04:00
fs xfs: fixes for 7.3-rc3 2026-09-12 08:44:12 -07:00
include Revert "KVM: Check for duplicate vcpu_id as early as possible" 2026-09-26 00:49:49 -04:00
init Bootconfig fixes for v7.3-rc3 2026-09-13 09:16:36 -07:00
io_uring io_uring-7.3-20260911 2026-09-11 12:36:13 -07:00
ipc mm.git review status for master..mm-nonmm-stable 2026-08-23 08:07:11 -07:00
kernel tracing fixes for 7.3: 2026-09-13 12:27:00 -07:00
lib block-7.3-20260911 2026-09-11 12:38:44 -07:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm slab fixes for 7.3-rc2 2026-09-11 11:56:33 -07:00
net Nothing too exciting, usual stream of fixes. 2026-09-10 14:07:48 -07:00
rust Rust fixes for v7.3 (2nd) 2026-09-13 09:28:28 -07:00
samples rust: samples: add missing newlines in rust_print_main 2026-09-01 02:20:22 +02:00
scripts Fix misc objtool bugs: 2026-09-13 08:37:11 -07:00
security landlock: Test trace path output boundaries 2026-09-08 11:49:39 +02:00
sound sound fixes for 7.3-rc3 2026-09-11 10:00:07 -07:00
tools KVM: selftests: Extend nested x2APIC test to validate using eVMCS for vmcs12 2026-09-28 17:11:49 -04:00
usr usr: Correct a spelling by changing a letter 2026-08-05 14:51:58 +02:00
virt KVM: WARN if vCPU creation is in-progress when locking all vCPUs 2026-09-26 00:49:49 -04:00
.clang-format drm/bridge: rename drm_for_each_bridge_in_chain_scoped() to drm_for_each_bridge_in_chain() 2026-07-14 17:55:51 +02:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add Nathan Chancellor 2026-08-03 21:10:12 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore SPDX patches for 7.2-rc1 2026-06-22 12:06:22 -07:00
.mailmap mailmap: update entry for Jens Axboe 2026-09-11 15:41:26 -07:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS Driver core fixes for 7.3-rc2 2026-09-05 11:59:05 -07:00
Kbuild checksyscalls: move instance functionality into generic code 2026-04-05 09:21:32 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS IOMMU fixes for Linux v7.3-rc3: 2026-09-12 07:55:52 -07:00
Makefile Linux 7.3-rc3 2026-09-13 14:38:02 -07:00
README README: remove out of place emdashes 2026-07-15 10:51:29 -06:00

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