Merge tag 'x86_microcode_for_v6.1_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x75 microcode loader updates from Borislav Petkov:

 - Get rid of a single ksize() usage

 - By popular demand, print the previous microcode revision an update
   was done over

 - Remove more code related to the now gone MICROCODE_OLD_INTERFACE

 - Document the problems stemming from microcode late loading

* tag 'x86_microcode_for_v6.1_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/microcode/AMD: Track patch allocation size explicitly
  x86/microcode: Print previous version of microcode after reload
  x86/microcode: Remove ->request_microcode_user()
  x86/microcode: Document the whole late loading problem

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst
index 7d80e8c307d1..92a8a07f5c43 100644
--- a/Documentation/admin-guide/tainted-kernels.rst
+++ b/Documentation/admin-guide/tainted-kernels.rst
@@ -134,6 +134,12 @@ More detailed explanation for tainting
        scsi/snic on something else than x86_64, scsi/ips on non
        x86/x86_64/itanium, have broken firmware settings for the
        irqchip/irq-gic on arm64 ...).
+     - x86/x86_64: Microcode late loading is dangerous and will result in
+       tainting the kernel. It requires that all CPUs rendezvous to make sure
+       the update happens when the system is as quiescent as possible. However,
+       a higher priority MCE/SMI/NMI can move control flow away from that
+       rendezvous and interrupt the update, which can be detrimental to the
+       machine.
 
  3)  ``R`` if a module was force unloaded by ``rmmod -f``, ``' '`` if all
      modules were unloaded normally.