x86/ucode/AMD: apply the patch early on every logical thread

The original issue has been reported on AMD Bulldozer-based CPUs where
ucode loading loses the LWP feature bit in order to gain the IBPB bit.
LWP disabling is per-SMT/CMT core modification and needs to happen on
each sibling thread despite the shared microcode engine. Otherwise,
logical CPUs will end up with different cpuid capabilities.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216211
Guests running under Xen happen to be not affected because of levelling
logic for the feature masking/override MSRs which causes the LWP bit to
fall out and hides the issue. The latest recommendation from AMD, after
discussing this bug, is to load ucode on every logical CPU.

In Linux kernel this issue has been addressed by e7ad18d1169c
("x86/microcode/AMD: Apply the patch early on every logical thread").
Follow the same approach in Xen.

Introduce SAME_UCODE match result and use it for early AMD ucode
loading. Take this opportunity and move opt_ucode_allow_same out of
compare_revisions() to the relevant callers and also modify the warning
message based on it. Intel's side of things is modified for consistency
but provides no functional change.

Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/cpu/microcode/amd.c b/xen/arch/x86/cpu/microcode/amd.c
index 4b097187a05b4efcb2e6cc881c20492daeca4c6b..a9a5557835e458fc6c4674a23a6f37941742c028 100644 (file)
--- a/xen/arch/x86/cpu/microcode/amd.c
+++ b/xen/arch/x86/cpu/microcode/amd.c
@@ -176,8 +176,8 @@ static enum microcode_match_result compare_revisions(
     if ( new_rev > old_rev )
         return NEW_UCODE;
 
-    if ( opt_ucode_allow_same && new_rev == old_rev )
-        return NEW_UCODE;
+    if ( new_rev == old_rev )
+        return SAME_UCODE;
 
     return OLD_UCODE;
 }
@@ -220,8 +220,13 @@ static int cf_check apply_microcode(const struct microcode_patch *patch)
     unsigned int cpu = smp_processor_id();
     struct cpu_signature *sig = &per_cpu(cpu_sig, cpu);
     uint32_t rev, old_rev = sig->rev;
+    enum microcode_match_result result = microcode_fits(patch);
 
-    if ( microcode_fits(patch) != NEW_UCODE )
+    /*
+     * 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 ( result != NEW_UCODE && result != SAME_UCODE )
         return -EINVAL;
 
     if ( check_final_patch_levels(sig) )

diff --git a/xen/arch/x86/cpu/microcode/core.c b/xen/arch/x86/cpu/microcode/core.c
index d14754e222820aba46678bcbeb9efe3fb5d38903..ba6e7b42c652715abbcfce8230e04130ffdad08a 100644 (file)
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -612,17 +612,25 @@ static long cf_check microcode_update_helper(void *data)
      * that ucode revision.
      */
     spin_lock(&microcode_mutex);
-    if ( microcode_cache &&
-         alternative_call(ucode_ops.compare_patch,
-                          patch, microcode_cache) != NEW_UCODE )
+    if ( microcode_cache )
     {
-        spin_unlock(&microcode_mutex);
-        printk(XENLOG_WARNING "microcode: couldn't find any newer revision "
-                              "in the provided blob!\n");
-        microcode_free_patch(patch);
-        ret = -ENOENT;
+        enum microcode_match_result result;
 
-        goto put;
+        result = alternative_call(ucode_ops.compare_patch, patch,
+                                  microcode_cache);
+
+        if ( result != NEW_UCODE &&
+             !(opt_ucode_allow_same && result == SAME_UCODE) )
+        {
+            spin_unlock(&microcode_mutex);
+            printk(XENLOG_WARNING
+                   "microcode: couldn't find any newer%s revision in the provided blob!\n",
+                   opt_ucode_allow_same ? " (or the same)" : "");
+            microcode_free_patch(patch);
+            ret = -ENOENT;
+
+            goto put;
+        }
     }
     spin_unlock(&microcode_mutex);
 

diff --git a/xen/arch/x86/cpu/microcode/intel.c b/xen/arch/x86/cpu/microcode/intel.c
index f7fec4b4ed1066f4cb4cc4ba1a0b16b86ab66175..8d4d6574aa10b838025d5adba6403923ee6f9b40 100644 (file)
--- a/xen/arch/x86/cpu/microcode/intel.c
+++ b/xen/arch/x86/cpu/microcode/intel.c
@@ -232,8 +232,8 @@ static enum microcode_match_result compare_revisions(
     if ( new_rev > old_rev )
         return NEW_UCODE;
 
-    if ( opt_ucode_allow_same && new_rev == old_rev )
-        return NEW_UCODE;
+    if ( new_rev == old_rev )
+        return SAME_UCODE;
 
     /*
      * Treat pre-production as always applicable - anyone using pre-production
@@ -290,8 +290,12 @@ static int cf_check apply_microcode(const struct microcode_patch *patch)
     unsigned int cpu = smp_processor_id();
     struct cpu_signature *sig = &this_cpu(cpu_sig);
     uint32_t rev, old_rev = sig->rev;
+    enum microcode_match_result result;
+
+    result = microcode_update_match(patch);
 
-    if ( microcode_update_match(patch) != NEW_UCODE )
+    if ( result != NEW_UCODE &&
+         !(opt_ucode_allow_same && result == SAME_UCODE) )
         return -EINVAL;
 
     wbinvd();

diff --git a/xen/arch/x86/cpu/microcode/private.h b/xen/arch/x86/cpu/microcode/private.h
index 73b095d5bf5062875b1540cf81b6da274a8ebbad..626aeb4d0883dc486f2152f18b3a0c055b022933 100644 (file)
--- a/xen/arch/x86/cpu/microcode/private.h
+++ b/xen/arch/x86/cpu/microcode/private.h
@@ -6,7 +6,8 @@
 extern bool opt_ucode_allow_same;
 
 enum microcode_match_result {
-    OLD_UCODE, /* signature matched, but revision id is older or equal */
+    OLD_UCODE, /* signature matched, but revision id is older */
+    SAME_UCODE, /* signature matched, but revision id is the same */
     NEW_UCODE, /* signature matched, but revision id is newer */
     MIS_UCODE, /* signature mismatched */
 };