[xen master] x86/ucode/AMD: apply the patch early on every logical thread

[patchbot@xxxxxxx]

commit f4ef8a41b80831db2136bdaff9f946a1a4b051e7
Author:     Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
AuthorDate: Tue Feb 21 15:08:05 2023 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Feb 21 15:08:05 2023 +0100

    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@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/cpu/microcode/amd.c     | 11 ++++++++---
 xen/arch/x86/cpu/microcode/core.c    | 26 +++++++++++++++++---------
 xen/arch/x86/cpu/microcode/intel.c   | 10 +++++++---
 xen/arch/x86/cpu/microcode/private.h |  3 ++-
 4 files changed, 34 insertions(+), 16 deletions(-)

diff --git a/xen/arch/x86/cpu/microcode/amd.c b/xen/arch/x86/cpu/microcode/amd.c
index 4b097187a0..a9a5557835 100644
--- 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 d14754e222..ba6e7b42c6 100644
--- 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 f7fec4b4ed..8d4d6574aa 100644
--- 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 73b095d5bf..626aeb4d08 100644
--- 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 */
 };
--
generated by git-patchbot for /home/xen/git/xen.git#master