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Prior to commit 496121c02127 ("ACPI: processor: idle: Allow probing on
platforms with one ACPI C-state"), the acpi_idle driver wouldn't load on
systems without a valid C-State at least as deep as C2.
The behavior was desirable for guests on hypervisors such as VMWare
ESXi, which by default don't have the _CST ACPI method, and set the C2
and C3 latencies to 101 and 1001 microseconds respectively via the FADT,
to signify they're unsupported.
Since the above change though, these virtualized deployments end up
loading acpi_idle, and thus entering the default C1 C-State set by
acpi_processor_get_power_info_default(); this is undesirable for a
system that's communicating to the OS it doesn't want C-States (missing
_CST, and invalid C2/C3 in FADT).
Make acpi_processor_get_power_info_fadt() return -ENODEV in that case,
so that acpi_processor_get_cstate_info() exits early and doesn't set
pr->flags.power = 1.
Fixes: 496121c02127 ("ACPI: processor: idle: Allow probing on platforms with one ACPI C-state")
Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz>
Reviewed-by: Zhang Rui <rui.zhang@intel.com>
Link: https://patch.msgid.link/20250328143040.9348-1-ggherdovich@suse.cz
[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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 reStructuredText 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.