[Xen-devel] [PATCH v8 02/16] x86/microcode: always collect_cpu_info() during boot

[Chao Gao <chao.gao@xxxxxxxxx>]

From: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>

Currently cpu_sig struct is not updated during boot if no microcode blob
is specified by "ucode=[<interger>| scan]".

It will result in cpu_sig.rev being 0 which affects APIC's
check_deadline_errata() and retpoline_safe() functions.

Fix this by getting ucode revision early during boot and SMP bring up.
While at it, protect early_microcode_update_cpu() for cases when
microcode_ops is NULL.

Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
Changes in v8:
 - refine description.
 - Jan asked if we could drop the call of collect_cpu_info() from
 microcode_update_cpu(). In theory, yes, but should be placed later
 in the series. Because there is an error path (__microcode_fini_cpu())
 in which cpu_sig.rev is cleared, it is hard to make things right
 in all cases without removing the error path (which is done by following
 patches). Considering it is a good fix, put it here so that it can
 be merged without following patches.
---
 xen/arch/x86/microcode.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/xen/arch/x86/microcode.c b/xen/arch/x86/microcode.c
index 4163f50..421d57e 100644
--- a/xen/arch/x86/microcode.c
+++ b/xen/arch/x86/microcode.c
@@ -383,10 +383,15 @@ static struct notifier_block microcode_percpu_nfb = {
 
 int __init early_microcode_update_cpu(bool start_update)
 {
+    unsigned int cpu = smp_processor_id();
+    struct ucode_cpu_info *uci = &per_cpu(ucode_cpu_info, cpu);
     int rc = 0;
     void *data = NULL;
     size_t len;
 
+    if ( !microcode_ops )
+        return -ENOSYS;
+
     if ( ucode_blob.size )
     {
         len = ucode_blob.size;
@@ -397,6 +402,9 @@ int __init early_microcode_update_cpu(bool start_update)
         len = ucode_mod.mod_end;
         data = bootstrap_map(&ucode_mod);
     }
+
+    microcode_ops->collect_cpu_info(cpu, &uci->cpu_sig);
+
     if ( data )
     {
         if ( start_update && microcode_ops->start_update )
@@ -413,6 +421,8 @@ int __init early_microcode_update_cpu(bool start_update)
 
 int __init early_microcode_init(void)
 {
+    unsigned int cpu = smp_processor_id();
+    struct ucode_cpu_info *uci = &per_cpu(ucode_cpu_info, cpu);
     int rc;
 
     rc = microcode_init_intel();
@@ -425,6 +435,8 @@ int __init early_microcode_init(void)
 
     if ( microcode_ops )
     {
+        microcode_ops->collect_cpu_info(cpu, &uci->cpu_sig);
+
         if ( ucode_mod.mod_end || ucode_blob.size )
             rc = early_microcode_update_cpu(true);
 
-- 
1.8.3.1


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