Merge tag 'x86_microcode_for_v6.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 microcode loading updates from Borislav Petkov:

 - Add microcode staging support on Intel: it moves the sole microcode
   blobs loading to a non-critical path so that microcode loading
   latencies are kept at minimum. The actual "directing" the hardware to
   load microcode is the only step which is done on the critical path.

   This scheme is also opportunistic as in: on a failure, the machinery
   falls back to normal loading

 - Add the capability to the AMD side of the loader to select one of two
   per-family/model/stepping patches: one is pre-Entrysign and the other
   is post-Entrysign; with the goal to take care of machines which
   haven't updated their BIOS yet - something they should absolutely do
   as this is the only proper Entrysign fix

 - Other small cleanups and fixlets

* tag 'x86_microcode_for_v6.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/microcode: Mark early_parse_cmdline() as __init
  x86/microcode/AMD: Select which microcode patch to load
  x86/microcode/intel: Enable staging when available
  x86/microcode/intel: Support mailbox transfer
  x86/microcode/intel: Implement staging handler
  x86/microcode/intel: Define staging state struct
  x86/microcode/intel: Establish staging control logic
  x86/microcode: Introduce staging step to reduce late-loading time
  x86/cpu/topology: Make primary thread mask available with SMP=n

1 files changed, 12 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index f75c140906d0..ccc83b0bf63c 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -136,7 +136,7 @@ bool __init microcode_loader_disabled(void)
 	return dis_ucode_ldr;
 }
 
-static void early_parse_cmdline(void)
+static void __init early_parse_cmdline(void)
 {
 	char cmd_buf[64] = {};
 	char *s, *p = cmd_buf;
@@ -589,6 +589,17 @@ static int load_late_stop_cpus(bool is_safe)
 		pr_err("You should switch to early loading, if possible.\n");
 	}
 
+	/*
+	 * Pre-load the microcode image into a staging device. This
+	 * process is preemptible and does not require stopping CPUs.
+	 * Successful staging simplifies the subsequent late-loading
+	 * process, reducing rendezvous time.
+	 *
+	 * Even if the transfer fails, the update will proceed as usual.
+	 */
+	if (microcode_ops->use_staging)
+		microcode_ops->stage_microcode();
+
 	atomic_set(&late_cpus_in, num_online_cpus());
 	atomic_set(&offline_in_nmi, 0);
 	loops_per_usec = loops_per_jiffy / (TICK_NSEC / 1000);