[Xen-devel] [PATCH v4 1/6] microcode/intel: extend microcode_update_match()

[Chao Gao <chao.gao@xxxxxxxxx>]

to a more generic function. The benefit is that this function can be
used to check whether a microcode is newer than another as well. We
rely on this function to decide to perform a replacement or an add when
updating the global microcode cache (introduced by later patches in
this series).

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
 xen/arch/x86/microcode_intel.c | 57 +++++++++++++++++++++++-------------------
 1 file changed, 31 insertions(+), 26 deletions(-)

diff --git a/xen/arch/x86/microcode_intel.c b/xen/arch/x86/microcode_intel.c
index 9657575..8d9a3b2 100644
--- a/xen/arch/x86/microcode_intel.c
+++ b/xen/arch/x86/microcode_intel.c
@@ -127,14 +127,37 @@ static int collect_cpu_info(unsigned int cpu_num, struct 
cpu_signature *csig)
     return 0;
 }
 
-static inline int microcode_update_match(
-    unsigned int cpu_num, const struct microcode_header_intel *mc_header,
-    int sig, int pf)
+enum {
+    OLD_UCODE, /* signature matched, but revision id isn't newer */
+    NEW_UCODE, /* signature matched, but revision id is newer */
+    MIS_UCODE, /* signature mismatched */
+};
+
+static int microcode_update_match(const void *mc,
+        unsigned int sig, unsigned int pf, unsigned int rev)
 {
-    struct ucode_cpu_info *uci = &per_cpu(ucode_cpu_info, cpu_num);
+    const struct microcode_header_intel *mc_header = mc;
+    const struct extended_sigtable *ext_header;
+    unsigned long total_size = get_totalsize(mc_header);
+    int ext_sigcount, i;
+    struct extended_signature *ext_sig;
 
-    return (sigmatch(sig, uci->cpu_sig.sig, pf, uci->cpu_sig.pf) &&
-            (mc_header->rev > uci->cpu_sig.rev));
+    if ( sigmatch(sig, mc_header->sig, pf, mc_header->pf) )
+        return (mc_header->rev > rev) ? NEW_UCODE : OLD_UCODE;
+
+    if ( total_size <= (get_datasize(mc_header) + MC_HEADER_SIZE) )
+        return MIS_UCODE;
+
+    ext_header = mc + get_datasize(mc_header) + MC_HEADER_SIZE;
+    ext_sigcount = ext_header->count;
+    ext_sig = (void *)ext_header + EXT_HEADER_SIZE;
+    for ( i = 0; i < ext_sigcount; i++ )
+    {
+        if ( sigmatch(sig, ext_sig->sig, pf, ext_sig->pf) )
+            return (mc_header->rev > rev) ? NEW_UCODE : OLD_UCODE;
+        ext_sig++;
+    }
+    return MIS_UCODE;
 }
 
 static int microcode_sanity_check(void *mc)
@@ -236,31 +259,13 @@ static int get_matching_microcode(const void *mc, 
unsigned int cpu)
 {
     struct ucode_cpu_info *uci = &per_cpu(ucode_cpu_info, cpu);
     const struct microcode_header_intel *mc_header = mc;
-    const struct extended_sigtable *ext_header;
     unsigned long total_size = get_totalsize(mc_header);
-    int ext_sigcount, i;
-    struct extended_signature *ext_sig;
     void *new_mc;
 
-    if ( microcode_update_match(cpu, mc_header,
-                                mc_header->sig, mc_header->pf) )
-        goto find;
-
-    if ( total_size <= (get_datasize(mc_header) + MC_HEADER_SIZE) )
+    if ( microcode_update_match(mc, uci->cpu_sig.sig, uci->cpu_sig.pf,
+                                uci->cpu_sig.rev) != NEW_UCODE )
         return 0;
 
-    ext_header = mc + get_datasize(mc_header) + MC_HEADER_SIZE;
-    ext_sigcount = ext_header->count;
-    ext_sig = (void *)ext_header + EXT_HEADER_SIZE;
-    for ( i = 0; i < ext_sigcount; i++ )
-    {
-        if ( microcode_update_match(cpu, mc_header,
-                                    ext_sig->sig, ext_sig->pf) )
-            goto find;
-        ext_sig++;
-    }
-    return 0;
- find:
     pr_debug("microcode: CPU%d found a matching microcode update with"
              " version %#x (current=%#x)\n",
              cpu, mc_header->rev, uci->cpu_sig.rev);
-- 
1.8.3.1


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