625872d22f
commit 6f5c9600621b4efb5c61b482d767432eb1ad3a9c upstream. Drop KVM's propagation of GuestPhysBits (CPUID leaf 80000008, EAX[23:16]) to HostPhysBits (same leaf, EAX[7:0]) when advertising the address widths to userspace via KVM_GET_SUPPORTED_CPUID. Per AMD, GuestPhysBits is intended for software use, and physical CPUs do not set that field. I.e. GuestPhysBits will be non-zero if and only if KVM is running as a nested hypervisor, and in that case, GuestPhysBits is NOT guaranteed to capture the CPU's effective MAXPHYADDR when running with TDP enabled. E.g. KVM will soon use GuestPhysBits to communicate the CPU's maximum *addressable* guest physical address, which would result in KVM under- reporting PhysBits when running as an L1 on a CPU with MAXPHYADDR=52, but without 5-level paging. Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Cc: stable@vger.kernel.org Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com> Link: https://lore.kernel.org/r/20240313125844.912415-2-kraxel@redhat.com [sean: rewrite changelog with --verbose, Cc stable@] Signed-off-by: Sean Christopherson <seanjc@google.com> 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.