[Xen-devel] [PATCH 2/2] x86: correct ordering of operations during S3 resume

[Simon Gaiser <simon@xxxxxxxxxxxxxxxxxxxxxx>]

Microcode loading needs to happen before re-enabling interrupts, in case
only updated microcode allows the use of e.g. the SPEC_{CTRL,CMD} MSRs.
Otoh it doesn't need to happen at all when we didn't suspend in the
first place. It needs to happen before spin_debug_enable() though, as it
acquires a lock and hence would otherwise make
common/spinlock.c:check_lock() unhappy. As microcode loading can be
pretty verbose, also make sure it only runs after console_end_sync().

cpufreq_add_cpu() doesn't need calling on the only "goto enable_cpu"
path, which sits ahead of cpufreq_del_cpu().

Reported-by: Simon Gaiser <simon@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
[Simon: Panic if microcode restore fails]
Signed-off-by: Simon Gaiser <simon@xxxxxxxxxxxxxxxxxxxxxx>
---
 xen/arch/x86/acpi/power.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/acpi/power.c b/xen/arch/x86/acpi/power.c
index 1e4e5680a7..0e00c198db 100644
--- a/xen/arch/x86/acpi/power.c
+++ b/xen/arch/x86/acpi/power.c
@@ -203,6 +203,7 @@ static int enter_state(u32 state)
         printk(XENLOG_ERR "Some devices failed to power down.");
         system_state = SYS_STATE_resume;
         device_power_up(error);
+        console_end_sync();
         error = -EIO;
         goto done;
     }
@@ -243,17 +244,21 @@ static int enter_state(u32 state)
     if ( (state == ACPI_STATE_S3) && error )
         tboot_s3_error(error);
 
+    console_end_sync();
+
+    error = microcode_resume_cpu(0);
+    if (error && error != -ENOENT)
+        panic("Could not restore microcode on boot cpu (%d)", error);
+
  done:
     spin_debug_enable();
     local_irq_restore(flags);
-    console_end_sync();
     acpi_sleep_post(state);
     if ( hvm_cpu_up() )
         BUG();
+    cpufreq_add_cpu(0);
 
  enable_cpu:
-    cpufreq_add_cpu(0);
-    microcode_resume_cpu(0);
     rcu_barrier();
     mtrr_aps_sync_begin();
     enable_nonboot_cpus();
-- 
2.16.2


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