From: Borislav Petkov bp@suse.de
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 | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)
--- a/arch/x86/kernel/cpu/microcode/amd.c +++ b/arch/x86/kernel/cpu/microcode/amd.c @@ -440,7 +440,13 @@ apply_microcode_early_amd(u32 cpuid_1_ea return ret;
native_rdmsr(MSR_AMD64_PATCH_LEVEL, rev, dummy); - if (rev >= mc->hdr.patch_id) + + /* + * Allow application of the same revision to pick up SMT-specific + * changes even if the revision of the other SMT thread is already + * up-to-date. + */ + if (rev > mc->hdr.patch_id) return ret;
if (!__apply_microcode_amd(mc)) { @@ -522,8 +528,12 @@ void load_ucode_amd_ap(unsigned int cpui
native_rdmsr(MSR_AMD64_PATCH_LEVEL, rev, dummy);
- /* Check whether we have saved a new patch already: */ - if (*new_rev && rev < mc->hdr.patch_id) { + /* + * Check whether a new patch has been saved already. Also, allow application of + * the same revision in order to pick up SMT-thread-specific configuration even + * if the sibling SMT thread already has an up-to-date revision. + */ + if (*new_rev && rev <= mc->hdr.patch_id) { if (!__apply_microcode_amd(mc)) { *new_rev = mc->hdr.patch_id; return;