x86/microcode: Attempt late loading only when new microcode is present

Return UCODE_NEW from the scanning functions to denote that new microcode
was found and only then attempt the expensive synchronization dance.

Reported-by: Emanuel Czirai <xftroxgpx@protonmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Emanuel Czirai <xftroxgpx@protonmail.com>
Tested-by: Ashok Raj <ashok.raj@intel.com>
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lkml.kernel.org/r/20180314183615.17629-1-bp@alien8.de

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 2aded9db1d42..32b8e5724f96 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -862,6 +862,7 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
         unsigned int leftover = size;
         unsigned int curr_mc_size = 0, new_mc_size = 0;
         unsigned int csig, cpf;
+        enum ucode_state ret = UCODE_OK;
 
         while (leftover) {
                 struct microcode_header_intel mc_header;
@@ -903,6 +904,7 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
                         new_mc  = mc;
                         new_mc_size = mc_size;
                         mc = NULL;      /* trigger new vmalloc */
+                        ret = UCODE_NEW;
                 }
 
                 ucode_ptr += mc_size;
@@ -932,7 +934,7 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
         pr_debug("CPU%d found a matching microcode update with version 0x%x (current=0x%x)\n",
                  cpu, new_rev, uci->cpu_sig.rev);
 
-        return UCODE_OK;
+        return ret;
 }
 
 static int get_ucode_fw(void *to, const void *from, size_t n)