c571a144ef
Rework CPUID 0x2.0 to be a normal CPUID leaf if it returns "01" in AL, i.e. EAX & 0xff, as a step towards removing KVM's stateful CPUID code altogether. Long ago, Intel documented CPUID 0x2.0 as being a stateful leaf, e.g. a version of the SDM circa 1995 states: The least-significant byte in register EAX (register AL) indicates the number of times the CPUID instruction must be executed with an input value of 2 to get a complete description of the processors's caches and TLBs. The Pentium Pro family of processors will return a 1. A 2000 version of the SDM only updated the paragraph to reference Intel's new processory family: The first member of the family of Pentium 4 processors will return a 1. Fast forward to the present, and Intel's SDM now states: The least-significant byte in register EAX (register AL) will always return 01H. Software should ignore this value and not interpret it as an information descriptor. AMD's APM simply states that CPUID 0x2 is reserved. Given that CPUID itself was introduced in the Pentium, odds are good that the only Intel CPU family that *maybe* implemented a stateful CPUID was the P5. Which obviously did not support VMX, or KVM. In other words, KVM's emulation of a stateful CPUID 0x2.0 has likely been dead code from the day it was introduced. This is backed up by commit |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| 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.