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

4 files changed, 28 insertions, 19 deletions

diff --git a/arch/x86/include/asm/microcode.h b/arch/x86/include/asm/microcode.h
index 7fb1047d61c7..6cf0e4cb7b97 100644
--- a/arch/x86/include/asm/microcode.h
+++ b/arch/x86/include/asm/microcode.h
@@ -39,6 +39,7 @@ struct device;
 
 enum ucode_state {
         UCODE_OK        = 0,
+        UCODE_NEW,
         UCODE_UPDATED,
         UCODE_NFOUND,
         UCODE_ERROR,
diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
index a998e1a7d46f..48179928ff38 100644
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -339,7 +339,7 @@ int __init save_microcode_in_initrd_amd(unsigned int cpuid_1_eax)
                 return -EINVAL;
 
         ret = load_microcode_amd(true, x86_family(cpuid_1_eax), desc.data, desc.size);
-        if (ret != UCODE_OK)
+        if (ret > UCODE_UPDATED)
                 return -EINVAL;
 
         return 0;
@@ -683,27 +683,35 @@ static enum ucode_state __load_microcode_amd(u8 family, const u8 *data,
 static enum ucode_state
 load_microcode_amd(bool save, u8 family, const u8 *data, size_t size)
 {
+        struct ucode_patch *p;
         enum ucode_state ret;
 
         /* free old equiv table */
         free_equiv_cpu_table();
 
         ret = __load_microcode_amd(family, data, size);
-
-        if (ret != UCODE_OK)
+        if (ret != UCODE_OK) {
                 cleanup();
+                return ret;
+        }
 
-#ifdef CONFIG_X86_32
-        /* save BSP's matching patch for early load */
-        if (save) {
-                struct ucode_patch *p = find_patch(0);
-                if (p) {
-                        memset(amd_ucode_patch, 0, PATCH_MAX_SIZE);
-                        memcpy(amd_ucode_patch, p->data, min_t(u32, ksize(p->data),
-                                                               PATCH_MAX_SIZE));
-                }
+        p = find_patch(0);
+        if (!p) {
+                return ret;
+        } else {
+                if (boot_cpu_data.microcode == p->patch_id)
+                        return ret;
+
+                ret = UCODE_NEW;
         }
-#endif
+
+        /* save BSP's matching patch for early load */
+        if (!save)
+                return ret;
+
+        memset(amd_ucode_patch, 0, PATCH_MAX_SIZE);
+        memcpy(amd_ucode_patch, p->data, min_t(u32, ksize(p->data), PATCH_MAX_SIZE));
+
         return ret;
 }
 
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 70ecbc8099c9..9f0fe5bb450d 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -607,7 +607,7 @@ static ssize_t reload_store(struct device *dev,
                 return size;
 
         tmp_ret = microcode_ops->request_microcode_fw(bsp, &microcode_pdev->dev, true);
-        if (tmp_ret != UCODE_OK)
+        if (tmp_ret != UCODE_NEW)
                 return size;
 
         get_online_cpus();
@@ -691,10 +691,8 @@ static enum ucode_state microcode_init_cpu(int cpu, bool refresh_fw)
         if (system_state != SYSTEM_RUNNING)
                 return UCODE_NFOUND;
 
-        ustate = microcode_ops->request_microcode_fw(cpu, &microcode_pdev->dev,
-                                                     refresh_fw);
-
-        if (ustate == UCODE_OK) {
+        ustate = microcode_ops->request_microcode_fw(cpu, &microcode_pdev->dev, refresh_fw);
+        if (ustate == UCODE_NEW) {
                 pr_debug("CPU%d updated upon init\n", cpu);
                 apply_microcode_on_target(cpu);
         }
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)