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Preserve CR0.CD and CR0.NW on INIT instead of forcing them to '1', as
defined by both Intel's SDM and AMD's APM.
Note, current versions of Intel's SDM are very poorly written with
respect to INIT behavior. Table 9-1. "IA-32 and Intel 64 Processor
States Following Power-up, Reset, or INIT" quite clearly lists power-up,
RESET, _and_ INIT as setting CR0=60000010H, i.e. CD/NW=1. But the SDM
then attempts to qualify CD/NW behavior in a footnote:
2. The CD and NW flags are unchanged, bit 4 is set to 1, all other bits
are cleared.
Presumably that footnote is only meant for INIT, as the RESET case and
especially the power-up case are rather non-sensical. Another footnote
all but confirms that:
6. Internal caches are invalid after power-up and RESET, but left
unchanged with an INIT.
Bare metal testing shows that CD/NW are indeed preserved on INIT (someone
else can hack their BIOS to check RESET and power-up :-D).
Reported-by: Reiji Watanabe <reijiw@google.com>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210713163324.627647-47-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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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.