[Xen-devel] [PATCH v10 15/16] microcode: disable late loading if CPUs are affected by BDF90

[Chao Gao <chao.gao@xxxxxxxxx>]

It ports the implementation of is_blacklisted() in linux kernel
to Xen.

Late loading may cause system hang if CPUs are affected by BDF90.
Check against BDF90 before performing a late loading.

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
 xen/arch/x86/microcode.c        |  6 ++++++
 xen/arch/x86/microcode_intel.c  | 23 +++++++++++++++++++++++
 xen/include/asm-x86/microcode.h |  1 +
 3 files changed, 30 insertions(+)

diff --git a/xen/arch/x86/microcode.c b/xen/arch/x86/microcode.c
index 64a4321..dbd2730 100644
--- a/xen/arch/x86/microcode.c
+++ b/xen/arch/x86/microcode.c
@@ -561,6 +561,12 @@ int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void) 
buf, unsigned long len)
     if ( microcode_ops == NULL )
         return -EINVAL;
 
+    if ( microcode_ops->is_blacklisted && microcode_ops->is_blacklisted() )
+    {
+        printk(XENLOG_WARNING "Late ucode loading is disabled!\n");
+        return -EPERM;
+    }
+
     buffer = xmalloc_bytes(len);
     if ( !buffer )
         return -ENOMEM;
diff --git a/xen/arch/x86/microcode_intel.c b/xen/arch/x86/microcode_intel.c
index 19f1ba0..bcef668 100644
--- a/xen/arch/x86/microcode_intel.c
+++ b/xen/arch/x86/microcode_intel.c
@@ -28,6 +28,7 @@
 #include <xen/smp.h>
 #include <xen/spinlock.h>
 
+#include <asm/div64.h>
 #include <asm/msr.h>
 #include <asm/processor.h>
 #include <asm/microcode.h>
@@ -283,6 +284,27 @@ static enum microcode_match_result compare_patch(
                                                              : OLD_UCODE;
 }
 
+static bool is_blacklisted(void)
+{
+    struct cpuinfo_x86 *c = &current_cpu_data;
+    uint64_t llc_size = c->x86_cache_size * 1024ULL;
+    struct cpu_signature *sig = &this_cpu(cpu_sig);
+
+    do_div(llc_size, c->x86_max_cores);
+
+    /*
+     * Late loading on model 79 with microcode revision less than 0x0b000021
+     * and LLC size per core bigger than 2.5MB may result in a system hang.
+     * This behavior is documented in item BDF90, #334165 (Intel Xeon
+     * Processor E7-8800/4800 v4 Product Family).
+     */
+    if ( c->x86 == 6 && c->x86_model == 0x4F && c->x86_mask == 0x1 &&
+         llc_size > 2621440 && sig->rev < 0x0b000021 )
+        return true;
+
+    return false;
+}
+
 static int apply_microcode(const struct microcode_patch *patch)
 {
     uint64_t msr_content;
@@ -415,6 +437,7 @@ static const struct microcode_ops microcode_intel_ops = {
     .free_patch                       = free_patch,
     .compare_patch                    = compare_patch,
     .match_cpu                        = match_cpu,
+    .is_blacklisted                   = is_blacklisted,
 };
 
 int __init microcode_init_intel(void)
diff --git a/xen/include/asm-x86/microcode.h b/xen/include/asm-x86/microcode.h
index 7d5a1f8..9ffd9d2 100644
--- a/xen/include/asm-x86/microcode.h
+++ b/xen/include/asm-x86/microcode.h
@@ -30,6 +30,7 @@ struct microcode_ops {
     bool (*match_cpu)(const struct microcode_patch *patch);
     enum microcode_match_result (*compare_patch)(
         const struct microcode_patch *new, const struct microcode_patch *old);
+    bool (*is_blacklisted)(void);
 };
 
 struct cpu_signature {
-- 
1.8.3.1


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