x86/cpufeatures: Add a CPU feature bit for MSR immediate form instructions

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The immediate form of MSR access instructions are primarily motivated
by performance, not code size: by having the MSR number in an immediate,
it is available *much* earlier in the pipeline, which allows the
hardware much more leeway about how a particular MSR is handled.

Use a scattered CPU feature bit for MSR immediate form instructions.

Suggested-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Link: https://lore.kernel.org/r/20250805202224.1475590-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

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Xin Li 2025-08-05 13:22:19 -07:00 • committed by Sean Christopherson

parent 6c3d4b9179

commit 3c7cb84145

2 changed files with 2 additions and 0 deletions

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arch/x86/include/asm/cpufeatures.h

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arch/x86/kernel/cpu/scattered.c

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