Microcode does not need to have the default size of 2000+48 bytes.

A corresponding patch has gone into Linux 2.6.19; this is the
port to Xen.

Signed-off-by: Kurt Garloff <kurt@garloff.de>
Reference: Patch to linux kernel from Sep 27 2006
> # User Shaohua Li <shaohua.li@intel.com>
> # Node ID 45898b908138b5d93c2cc7353f061ce54af145dc
> # Parent  f962eab7b82c9bf1a6da69571046e764f5128395
> [PATCH] x86 microcode: don't check the size
>
> IA32 manual says if micorcode update's size is 0, then the size is
> default size (2048 bytes). But this doesn't suggest all microcode
> update's size should be above 2048 bytes to me. We actually had a
> microcode update whose size is 1024 bytes. The patch just removed
> the check.
>
> Signed-off-by: Shaohua Li <shaohua.li@intel.com>
> Cc: Tigran Aivazian <tigran@veritas.com>
> Signed-off-by: Andrew Morton <akpm@osdl.org>
> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
>
> committer: Linus Torvalds <torvalds@g5.osdl.org> 1159370778 -0700

diff --git a/xen/arch/x86/microcode.c b/xen/arch/x86/microcode.c
index 3dcac7d124cebdc87fb2cebe5b3a675ab29c530e..89138c9a799a8f4ee4d75b5512261e5d6b183b32 100644 (file)
--- a/xen/arch/x86/microcode.c
+++ b/xen/arch/x86/microcode.c
@@ -249,14 +249,14 @@ static int find_matching_ucodes (void)
                }
 
                total_size = get_totalsize(&mc_header);
-               if ((cursor + total_size > user_buffer_size) || (total_size < DEFAULT_UCODE_TOTALSIZE)) {
+               if (cursor + total_size > user_buffer_size) {
                        printk(KERN_ERR "microcode: error! Bad data in microcode data file\n");
                        error = -EINVAL;
                        goto out;
                }
 
                data_size = get_datasize(&mc_header);
-               if ((data_size + MC_HEADER_SIZE > total_size) || (data_size < DEFAULT_UCODE_DATASIZE)) {
+               if (data_size + MC_HEADER_SIZE > total_size) {
                        printk(KERN_ERR "microcode: error! Bad data in microcode data file\n");
                        error = -EINVAL;
                        goto out;
@@ -459,11 +459,6 @@ int microcode_update(XEN_GUEST_HANDLE(void) buf, unsigned long len)
 {
        int ret;
 
-       if (len < DEFAULT_UCODE_TOTALSIZE) {
-               printk(KERN_ERR "microcode: not enough data\n");
-               return -EINVAL;
-       }
-
        if (len != (typeof(user_buffer_size))len) {
                printk(KERN_ERR "microcode: too much data\n");
                return -E2BIG;