x86/microcode: Add a microcode loader callback

From: Borislav Petkov <[email protected]>

Add a callback which the microcode loader calls after microcode has been upgraded late to let the user know that any CPUID changes potentially won't take effect.

One possible example for this is that late loading happens after alternatives have run and thus patching which relies on those new CPUID features won't happen.

@Ashok: I haven't added your tags yet because I did a small change to run the callback only when no error has been encountered during loading. Please run them on your setup to confirm everything's still fine.

Thanks.

Borislav Petkov (3):
x86/microcode: Propagate return value from updating functions x86/CPU: Add a microcode loader callback
x86/CPU: Check CPU feature bits after microcode upgrade

 arch/x86/include/asm/microcode.h      |  9 ++++++--
 arch/x86/include/asm/processor.h      |  1 +
 arch/x86/kernel/cpu/common.c          | 30 +++++++++++++++++++++++++++
 arch/x86/kernel/cpu/microcode/amd.c   | 10 ++++-----
 arch/x86/kernel/cpu/microcode/core.c  | 39 ++++++++++++++++++++---------------
 arch/x86/kernel/cpu/microcode/intel.c | 10 ++++-----
 6 files changed, 70 insertions(+), 29 deletions(-)

2.13.0