cc95b5d240
commit be8de49bea505e7777a69ef63d60e02ac1712683 upstream. 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 sibling thread could use return target predictions from the sibling thread that transitioned out of C0. 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. A guest could act maliciously in this situation, so create a new x86 BUG that can be used to detect if the processor is vulnerable. Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> Message-Id: <91cec885656ca1fcd4f0185ce403a53dd9edecb7.1675956146.git.thomas.lendacky@amd.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.