x86 microcode: revert some work_on_cpu

Revert part of af5c820a3169e81af869c113e18ec7588836cd50 ("x86: cpumask:
use work_on_cpu in arch/x86/kernel/microcode_core.c")

That change is causing only one Intel CPU's microcode to be updated e.g.
microcode: CPU3 updated from revision 0x9 to 0x17, date = 2005-04-22
where before it announced that also for CPU0 and CPU1 and CPU2.

We cannot use work_on_cpu() in the CONFIG_MICROCODE_OLD_INTERFACE code,
because Intel's request_microcode_user() involves a copy_from_user() from
/sbin/microcode_ctl, which therefore needs to be on that CPU at the time.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 22 deletions

diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
index a0f3851ef310..2e0eb4140951 100644
--- a/arch/x86/kernel/microcode_core.c
+++ b/arch/x86/kernel/microcode_core.c
@@ -108,40 +108,29 @@ struct ucode_cpu_info		ucode_cpu_info[NR_CPUS];
 EXPORT_SYMBOL_GPL(ucode_cpu_info);
 
 #ifdef CONFIG_MICROCODE_OLD_INTERFACE
-struct update_for_cpu {
-        const void __user       *buf;
-        size_t                  size;
-};
-
-static long update_for_cpu(void *_ufc)
-{
-        struct update_for_cpu *ufc = _ufc;
-        int error;
-
-        error = microcode_ops->request_microcode_user(smp_processor_id(),
-                                                      ufc->buf, ufc->size);
-        if (error < 0)
-                return error;
-        if (!error)
-                microcode_ops->apply_microcode(smp_processor_id());
-        return error;
-}
-
 static int do_microcode_update(const void __user *buf, size_t size)
 {
+        cpumask_t old;
         int error = 0;
         int cpu;
-        struct update_for_cpu ufc = { .buf = buf, .size = size };
+
+        old = current->cpus_allowed;
 
         for_each_online_cpu(cpu) {
                 struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 
                 if (!uci->valid)
                         continue;
-                error = work_on_cpu(cpu, update_for_cpu, &ufc);
+
+                set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
+                error = microcode_ops->request_microcode_user(cpu, buf, size);
                 if (error < 0)
-                        break;
+                        goto out;
+                if (!error)
+                        microcode_ops->apply_microcode(cpu);
         }
+out:
+        set_cpus_allowed_ptr(current, &old);
         return error;
 }