x86/bugs: Read SPEC_CTRL MSR during boot and re-use reserved bits

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commit 1b86883ccb upstream

The 336996-Speculative-Execution-Side-Channel-Mitigations.pdf refers to all
the other bits as reserved. The Intel SDM glossary defines reserved as
implementation specific - aka unknown.

As such at bootup this must be taken it into account and proper masking for
the bits in use applied.

A copy of this document is available at
https://bugzilla.kernel.org/show_bug.cgi?id=199511

[ tglx: Made x86_spec_ctrl_base __ro_after_init ]

Suggested-by: Jon Masters <jcm@redhat.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Konrad Rzeszutek Wilk 2018-04-25 22:04:18 -04:00 • committed by Greg Kroah-Hartman

parent 3ce1634f61

commit 7c9b4959cd

2 changed files with 48 additions and 4 deletions

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24

arch/x86/include/asm/nospec-branch.h

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28

arch/x86/kernel/cpu/bugs.c

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