[Xen-devel] [PATCH v8 03/16] microcode/intel: extend microcode_update_match()

[Chao Gao <chao.gao@xxxxxxxxx>]

to a more generic function. Then, this function can compare two given
microcodes' signature/revision as well. Comparing two microcodes is
used to update the global microcode cache (introduced by the later
patches in this series) when a new microcode is given.

Note that enum microcode_match_result will be used in common code
(aka microcode.c), it has been placed in the common header.

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes in v8:
 - make sure enough room for an extended header and signature array

Changes in v6:
 - eliminate unnecessary type casting in microcode_update_match
 - check if a patch has an extend header

Changes in v5:
 - constify the extended_signature
 - use named enum type for the return value of microcode_update_match
---
 xen/arch/x86/microcode_intel.c  | 57 ++++++++++++++++++++++-------------------
 xen/include/asm-x86/microcode.h |  6 +++++
 2 files changed, 36 insertions(+), 27 deletions(-)

diff --git a/xen/arch/x86/microcode_intel.c b/xen/arch/x86/microcode_intel.c
index 22fdeca..644660d 100644
--- a/xen/arch/x86/microcode_intel.c
+++ b/xen/arch/x86/microcode_intel.c
@@ -134,14 +134,35 @@ 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)
+static enum microcode_match_result microcode_update_match(
+    const struct microcode_header_intel *mc_header, unsigned int sig,
+    unsigned int pf, unsigned int rev)
 {
-    struct ucode_cpu_info *uci = &per_cpu(ucode_cpu_info, cpu_num);
-
-    return (sigmatch(sig, uci->cpu_sig.sig, pf, uci->cpu_sig.pf) &&
-            (mc_header->rev > uci->cpu_sig.rev));
+    const struct extended_sigtable *ext_header;
+    const struct extended_signature *ext_sig;
+    unsigned long data_size = get_datasize(mc_header);
+    unsigned int i;
+    const void *end = (const void *)mc_header + get_totalsize(mc_header);
+
+    if ( sigmatch(sig, mc_header->sig, pf, mc_header->pf) )
+        return (mc_header->rev > rev) ? NEW_UCODE : OLD_UCODE;
+
+    ext_header = (const void *)(mc_header + 1) + data_size;
+    ext_sig = (const void *)(ext_header + 1);
+
+    /*
+     * Make sure there is enough space to hold an extended header and enough
+     * array elements.
+     */
+    if ( (end < (const void *)ext_sig) ||
+         (end < (const void *)(ext_sig + ext_header->count)) )
+        return MIS_UCODE;
+
+    for ( i = 0; i < ext_header->count; i++ )
+        if ( sigmatch(sig, ext_sig[i].sig, pf, ext_sig[i].pf) )
+            return (mc_header->rev > rev) ? NEW_UCODE : OLD_UCODE;
+
+    return MIS_UCODE;
 }
 
 static int microcode_sanity_check(void *mc)
@@ -243,31 +264,13 @@ 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);
diff --git a/xen/include/asm-x86/microcode.h b/xen/include/asm-x86/microcode.h
index 23ea954..882f560 100644
--- a/xen/include/asm-x86/microcode.h
+++ b/xen/include/asm-x86/microcode.h
@@ -3,6 +3,12 @@
 
 #include <xen/percpu.h>
 
+enum microcode_match_result {
+    OLD_UCODE, /* signature matched, but revision id is older or equal */
+    NEW_UCODE, /* signature matched, but revision id is newer */
+    MIS_UCODE, /* signature mismatched */
+};
+
 struct cpu_signature;
 struct ucode_cpu_info;
 
-- 
1.8.3.1


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