x86, microcode, AMD: Add a reusable buffer

Add a simple 4K page which gets allocated on driver init and freed on
driver exit instead of vmalloc'ing small buffers for each ucode patch.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/x86/kernel/microcode_amd.c b/arch/x86/kernel/microcode_amd.c
index e8a68c2a4364..9129c6981c5b 100644
--- a/arch/x86/kernel/microcode_amd.c
+++ b/arch/x86/kernel/microcode_amd.c
@@ -71,6 +71,9 @@ struct microcode_amd {
 
 static struct equiv_cpu_entry *equiv_cpu_table;
 
+/* page-sized ucode patch buffer */
+void *patch;
+
 static int collect_cpu_info_amd(int cpu, struct cpu_signature *csig)
 {
         struct cpuinfo_x86 *c = &cpu_data(cpu);
@@ -351,9 +354,14 @@ static struct microcode_ops microcode_amd_ops = {
 
 struct microcode_ops * __init init_amd_microcode(void)
 {
+        patch = (void *)get_zeroed_page(GFP_KERNEL);
+        if (!patch)
+                return NULL;
+
         return &microcode_amd_ops;
 }
 
 void __exit exit_amd_microcode(void)
 {
+        free_page((unsigned long)patch);
 }