diff options
Diffstat (limited to 'src/cpu/x86')
| -rw-r--r-- | src/cpu/x86/sipi_vector.S | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/src/cpu/x86/sipi_vector.S b/src/cpu/x86/sipi_vector.S index 02ad0d367a..e1b90890ed 100644 --- a/src/cpu/x86/sipi_vector.S +++ b/src/cpu/x86/sipi_vector.S @@ -102,6 +102,13 @@ _start: /* Save CPU number. */ mov %ecx, %esi + /* + * The following code only needs to run on Intel platforms and thus the caller + * doesn't provide a microcode_ptr if not on Intel. + * On Intel platforms which update microcode using FIT the version check will + * also skip the microcode update. + */ + /* Determine if one should check microcode versions. */ mov microcode_ptr, %edi test %edi, %edi @@ -116,6 +123,16 @@ _start: test %edx, %edx jnz microcode_done + /* + * Intel SDM and various BWGs specify to use a semaphore to update microcode + * on one thread per core on Hyper-Threading enabled CPUs. Due to this complex + * code would be necessary to determine the core #ID, initializing and picking + * the right semaphore out of CONFIG_MAX_CPUS / 2. + * Instead of the per core approachm, as recommended, use one global spinlock. + * Assuming that only pre-FIT platforms with Hyper-Threading enabled and at + * most 8 threads will ever run into this condition, the boot delay is negligible. + */ + /* Determine if parallel microcode loading is allowed. */ cmpl $0xffffffff, microcode_lock je load_microcode |