x86/cpu: Add the 'setcpuid=' boot parameter

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In preparation for adding support to inject fake CPU bugs at boot-time,
add a general facility to force enablement of CPU flags.

The flag taints the kernel and the documentation attempts to be clear
that this is highly unsuitable for uses outside of kernel development
and platform experimentation.

The new arg is parsed just like clearcpuid, but instead of leading to
setup_clear_cpu_cap() it leads to setup_force_cpu_cap().

I've tested this by booting a nested QEMU guest on an Intel host, which
with setcpuid=svm will claim that it supports AMD virtualization.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20241220-force-cpu-bug-v2-2-7dc71bce742a@google.com

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Brendan Jackman 2024-12-20 15:18:32 +00:00 • committed by Ingo Molnar

parent f034937f5a

commit 814165e9fd

1 changed files with 26 additions and 9 deletions

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arch/x86/kernel/cpu/common.c

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