lwn.git/Documentation/admin-guide/hw-vuln/index.rst, branch docs-mw

Documentation/hw-vuln: Add VMSCAPE documentation

2025-08-14T17:26:03+00:00

VMSCAPE is a vulnerability that may allow a guest to influence the branch prediction in host userspace, particularly affecting hypervisors like QEMU. Add the documentation. Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Borislav Petkov (AMD) Reviewed-by: Dave Hansen

Documentation/x86: Document new attack vector controls

2025-07-11T15:51:43+00:00

Document the 5 new attack vector command line options, how they interact with existing vulnerability controls, and recommendations on when they can be disabled. Note that while mitigating against untrusted userspace requires both user-to-kernel and user-to-user protection, these are kept separate. The kernel can control what code executes inside of it and that may affect the risk associated with vulnerabilities especially if new kernel mitigations are implemented. The same isn't typically true of userspace. In other words, the risk associated with user-to-user or guest-to-guest attacks is unlikely to change over time. While the risk associated with user-to-kernel or guest-to-host attacks may change. Therefore, these controls are separated. Signed-off-by: David Kaplan Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/20250709155731.3279419-1-david.kaplan@amd.com

Merge commit 'its-for-linus-20250509-merge' into x86/core, to resolve conflicts

2025-05-13T08:47:10+00:00

Conflicts: Documentation/admin-guide/hw-vuln/index.rst arch/x86/include/asm/cpufeatures.h arch/x86/kernel/alternative.c arch/x86/kernel/cpu/bugs.c arch/x86/kernel/cpu/common.c drivers/base/cpu.c include/linux/cpu.h Signed-off-by: Ingo Molnar

Documentation: x86/bugs/its: Add ITS documentation

2025-05-09T20:22:04+00:00

Add the admin-guide for Indirect Target Selection (ITS). Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Josh Poimboeuf Reviewed-by: Alexandre Chartre

x86/cpu: Add "Old Microcode" docs to hw-vuln toctree

2025-05-02T18:33:35+00:00

Sphinx reports missing toctree entry warning: Documentation/admin-guide/hw-vuln/old_microcode.rst: WARNING: document isn't included in any toctree Add entry for "Old Microcode" docs to fix the warning. Fixes: 4e2c719782a847 ("x86/cpu: Help users notice when running old Intel microcode") Signed-off-by: Bagas Sanjaya Signed-off-by: Dave Hansen Link: https://lore.kernel.org/all/20250502023358.14846-1-bagasdotme%40gmail.com

x86/bugs: Add RSB mitigation document

2025-04-09T10:42:09+00:00

Create a document to summarize hard-earned knowledge about RSB-related mitigations, with references, and replace the overly verbose yet incomplete comments with a reference to the document. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/ab73f4659ba697a974759f07befd41ae605e33dd.1744148254.git.jpoimboe@kernel.org

Documentation/hw-vuln: Add documentation for RFDS

2024-03-11T20:13:46+00:00

Add the documentation for transient execution vulnerability Register File Data Sampling (RFDS) that affects Intel Atom CPUs. Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Thomas Gleixner Acked-by: Josh Poimboeuf

Documentation/hw-vuln: Unify filename specification in index

2023-08-10T08:48:12+00:00

Most of the index.rst files in Documentation/ refer to other rst files without their file extension in the name. Do that here too. No functional changes. Reported-by: Linus Torvalds Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Greg Kroah-Hartman Link: https://lore.kernel.org/r/20230809102700.29449-2-bp@alien8.de

Merge tag 'gds-for-linus-2023-08-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2023-08-08T00:03:54+00:00

Pull x86/gds fixes from Dave Hansen: "Mitigate Gather Data Sampling issue: - Add Base GDS mitigation - Support GDS_NO under KVM - Fix a documentation typo" * tag 'gds-for-linus-2023-08-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: Documentation/x86: Fix backwards on/off logic about YMM support KVM: Add GDS_NO support to KVM x86/speculation: Add Kconfig option for GDS x86/speculation: Add force option to GDS mitigation x86/speculation: Add Gather Data Sampling mitigation

x86/srso: Add a Speculative RAS Overflow mitigation

2023-07-27T09:07:14+00:00

Add a mitigation for the speculative return address stack overflow vulnerability found on AMD processors. The mitigation works by ensuring all RET instructions speculate to a controlled location, similar to how speculation is controlled in the retpoline sequence. To accomplish this, the __x86_return_thunk forces the CPU to mispredict every function return using a 'safe return' sequence. To ensure the safety of this mitigation, the kernel must ensure that the safe return sequence is itself free from attacker interference. In Zen3 and Zen4, this is accomplished by creating a BTB alias between the untraining function srso_untrain_ret_alias() and the safe return function srso_safe_ret_alias() which results in evicting a potentially poisoned BTB entry and using that safe one for all function returns. In older Zen1 and Zen2, this is accomplished using a reinterpretation technique similar to Retbleed one: srso_untrain_ret() and srso_safe_ret(). Signed-off-by: Borislav Petkov (AMD)