82eac0c830
predictions bug. When running in SMT mode and one of the sibling threads transitions out of C0 state, the other thread gets access to twice as many entries in the RSB, but unfortunately the predictions of the now-halted logical processor are not purged. Therefore, the executing processor could speculatively execute from locations that the now-halted processor had trained the RSB on. The Spectre v2 mitigations cover the Linux kernel, as it fills the RSB when context switching to the idle thread. However, KVM allows a VMM to prevent exiting guest mode when transitioning out of C0 using the KVM_CAP_X86_DISABLE_EXITS capability can be used by a VMM to change this behavior. To mitigate the cross-thread return address predictions bug, a VMM must not be allowed to override the default behavior to intercept C0 transitions. These patches introduce a KVM module parameter that, if set, will prevent the user from disabling the HLT, MWAIT and CSTATE exits. -----BEGIN PGP SIGNATURE----- iQFIBAABCAAyFiEE8TM4V0tmI4mGbHaCv/vSX3jHroMFAmPrvAAUHHBib256aW5p QHJlZGhhdC5jb20ACgkQv/vSX3jHroMQAgf8CirL+yrngzQ+39UTFQgXj3IS1UyR o2mF39w3bVlQhLNf5MBHF965FUeOV/8A16x73hJGjhiiuisphtQWS/6xKR6uYbq7 0Qi821skqN6XpRsWTWqFHMsdY+n0skr8QeXG4k/GJu7Ghb3tqs4eTGgnf2WBfI8/ K1UgTmjd9+ikM5gKZoVLpcqZnti0gx3lM+cvZGdfrIUaXB+i+hNd2NfRTiGsTOiK fX7vZtLvOeje2TPoKLhzekTbh8kTU07HRWID9aVXT8bLy6Zd6tg2CHlv11noKpwv DFVV+RsJ1SiAQYSwT+4IvWfIG4oq4onBQ972g2a27pP2cxF+38GXzt4NQw== =xscg -----END PGP SIGNATURE----- Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm Pull kvm fixes from Paolo Bonzini: "Certain AMD processors are vulnerable to a cross-thread return address predictions bug. When running in SMT mode and one of the sibling threads transitions out of C0 state, the other thread gets access to twice as many entries in the RSB, but unfortunately the predictions of the now-halted logical processor are not purged. Therefore, the executing processor could speculatively execute from locations that the now-halted processor had trained the RSB on. The Spectre v2 mitigations cover the Linux kernel, as it fills the RSB when context switching to the idle thread. However, KVM allows a VMM to prevent exiting guest mode when transitioning out of C0 using the KVM_CAP_X86_DISABLE_EXITS capability can be used by a VMM to change this behavior. To mitigate the cross-thread return address predictions bug, a VMM must not be allowed to override the default behavior to intercept C0 transitions. These patches introduce a KVM module parameter that, if set, will prevent the user from disabling the HLT, MWAIT and CSTATE exits" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: Documentation/hw-vuln: Add documentation for Cross-Thread Return Predictions KVM: x86: Mitigate the cross-thread return address predictions bug x86/speculation: Identify processors vulnerable to SMT RSB predictions |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.