x86/microcode/AMD: Apply the patch early on every logical thread
authorBorislav Petkov <bp@suse.de>
Wed, 5 Oct 2022 10:00:08 +0000 (12:00 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sat, 29 Oct 2022 08:12:54 +0000 (10:12 +0200)
commit2f7171465f2638e295e400a5d26261a31588d040
treecbedf2979706f3f97f6c6cd3dbb0bb685f890247
parent93d7e2b47a72f91be1b4e9ce9ce667fe801824bf
x86/microcode/AMD: Apply the patch early on every logical thread

commit e7ad18d1169c62e6c78c01ff693fd362d9d65278 upstream.

Currently, the patch application logic checks whether the revision
needs to be applied on each logical CPU (SMT thread). Therefore, on SMT
designs where the microcode engine is shared between the two threads,
the application happens only on one of them as that is enough to update
the shared microcode engine.

However, there are microcode patches which do per-thread modification,
see Link tag below.

Therefore, drop the revision check and try applying on each thread. This
is what the BIOS does too so this method is very much tested.

Btw, change only the early paths. On the late loading paths, there's no
point in doing per-thread modification because if is it some case like
in the bugzilla below - removing a CPUID flag - the kernel cannot go and
un-use features it has detected are there early. For that, one should
use early loading anyway.

  [ bp: Fixes does not contain the oldest commit which did check for
    equality but that is good enough. ]

Fixes: 8801b3fcb574 ("x86/microcode/AMD: Rework container parsing")
Reported-by: Ștefan Talpalaru <stefantalpalaru@yahoo.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Ștefan Talpalaru <stefantalpalaru@yahoo.com>
Cc: <stable@vger.kernel.org>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216211
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arch/x86/kernel/cpu/microcode/amd.c