[Xen-devel] [PATCH v6 05/12] microcode: only save compatible ucode patches

[Chao Gao <chao.gao@xxxxxxxxx>]

Intel CPU only allows mixing in stepping or 'pf'. If an ucode patch is
for other CPU families or models, it won't be compatible to all CPUs on
current system and even hot-plugged CPUs.  Don't save such patch to
reduce the size of ucode cache.

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
v6:
 - new
---
 xen/arch/x86/microcode.c        |  8 ++++++++
 xen/arch/x86/microcode_intel.c  | 35 +++++++++++++++++++++++++++++++++++
 xen/include/asm-x86/microcode.h |  1 +
 3 files changed, 44 insertions(+)

diff --git a/xen/arch/x86/microcode.c b/xen/arch/x86/microcode.c
index e629e6c..9ffbb15 100644
--- a/xen/arch/x86/microcode.c
+++ b/xen/arch/x86/microcode.c
@@ -243,6 +243,14 @@ bool microcode_save_patch(struct microcode_patch *new)
         else /* result == MIS_UCODE */
             continue;
     }
+
+    if ( microcode_ops->is_patch_compatible &&
+         !microcode_ops->is_patch_compatible(new) )
+    {
+        xfree(new);
+        return false;
+    }
+
     list_add_tail(&new->list, &microcode_cache);
 
     return true;
diff --git a/xen/arch/x86/microcode_intel.c b/xen/arch/x86/microcode_intel.c
index b556d3d..d973634 100644
--- a/xen/arch/x86/microcode_intel.c
+++ b/xen/arch/x86/microcode_intel.c
@@ -93,6 +93,8 @@ struct extended_sigtable {
 
 #define exttable_size(et) ((et)->count * EXT_SIGNATURE_SIZE + EXT_HEADER_SIZE)
 
+#define STEPPING_MASK ~0xfU
+
 /* serialize access to the physical write to MSR 0x79 */
 static DEFINE_SPINLOCK(microcode_update_lock);
 
@@ -167,6 +169,38 @@ static bool match_cpu(const struct microcode_patch *patch)
     return ret == NEW_UCODE;
 }
 
+/*
+ * Make sure the patch is compatible with current system. It depends on
+ * how much difference current CPU and the patch's supported CPUs have.
+ *
+ * For Intel cpu, make sure that the patch can be applied to a cpu which has
+ * the same family and model as current CPU.
+ */
+static bool is_patch_compatible(const struct microcode_patch *patch)
+{
+    struct ucode_cpu_info *uci = &this_cpu(ucode_cpu_info);
+    const struct cpu_signature *csig = &uci->cpu_sig;
+    const struct microcode_header_intel *mc_header = patch->data;
+    const struct extended_sigtable *ext_header;
+    const struct extended_signature *ext_sig;
+    unsigned long data_size = get_datasize(mc_header);
+    unsigned int i;
+
+    if ( (csig->sig & STEPPING_MASK) == (mc_header->sig & STEPPING_MASK) )
+        return true;
+
+    if ( get_totalsize(mc_header) == (data_size + MC_HEADER_SIZE) )
+        return false;
+
+    ext_header = (const void *)(mc_header + 1) + data_size;
+    ext_sig = (const void *)(ext_header + 1);
+    for ( i = 0; i < ext_header->count; i++ )
+        if ( (csig->sig & STEPPING_MASK) == (ext_sig[i].sig & STEPPING_MASK) )
+            return true;
+
+    return false;
+}
+
 static int microcode_sanity_check(void *mc)
 {
     struct microcode_header_intel *mc_header = mc;
@@ -456,6 +490,7 @@ static const struct microcode_ops microcode_intel_ops = {
     .compare_patch                    = compare_patch,
     .free_patch                       = free_patch,
     .match_cpu                        = match_cpu,
+    .is_patch_compatible              = is_patch_compatible,
 };
 
 int __init microcode_init_intel(void)
diff --git a/xen/include/asm-x86/microcode.h b/xen/include/asm-x86/microcode.h
index 7ff42fe..92631b4 100644
--- a/xen/include/asm-x86/microcode.h
+++ b/xen/include/asm-x86/microcode.h
@@ -29,6 +29,7 @@ struct microcode_ops {
         const struct microcode_patch *new, const struct microcode_patch *old);
     void (*free_patch)(struct microcode_patch *patch);
     bool (*match_cpu)(const struct microcode_patch *patch);
+    bool (*is_patch_compatible)(const struct microcode_patch *patch);
 };
 
 struct cpu_signature {
-- 
1.8.3.1


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