[Xen-devel] [PATCH v8 16/16] microcode: block #NMI handling when loading an ucode

[Chao Gao <chao.gao@xxxxxxxxx>]

register an nmi callback. And this callback does busy-loop on threads
which are waiting for loading completion if 'loading_ucode' is true.

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
Changes in v8:
 - new
---
 xen/arch/x86/microcode.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/xen/arch/x86/microcode.c b/xen/arch/x86/microcode.c
index 67549be..4ac7e93 100644
--- a/xen/arch/x86/microcode.c
+++ b/xen/arch/x86/microcode.c
@@ -38,6 +38,7 @@
 
 #include <asm/delay.h>
 #include <asm/msr.h>
+#include <asm/nmi.h>
 #include <asm/processor.h>
 #include <asm/setup.h>
 #include <asm/microcode.h>
@@ -439,12 +440,37 @@ static int do_microcode_update(void *patch)
     return ret;
 }
 
+static int microcode_nmi_callback(const struct cpu_user_regs *regs, int cpu)
+{
+    bool print = false;
+
+    /* The first thread of a core is to load an update. Don't block it. */
+    if ( cpu == cpumask_first(per_cpu(cpu_sibling_mask, cpu)) )
+        return 0;
+
+    if ( loading_state == LOADING_ENTERED )
+    {
+        cpumask_set_cpu(cpu, &cpu_callin_map);
+        printk(XENLOG_DEBUG "CPU%u enters %s\n", smp_processor_id(), __func__);
+        print = true;
+    }
+
+    while ( loading_state == LOADING_ENTERED )
+        rep_nop();
+
+    if ( print )
+        printk(XENLOG_DEBUG "CPU%u exits %s\n", smp_processor_id(), __func__);
+
+    return 0;
+}
+
 int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void) buf, unsigned long len)
 {
     int ret;
     void *buffer;
     unsigned int cpu, updated;
     struct microcode_patch *patch;
+    nmi_callback_t *saved_nmi_callback;
 
     if ( len != (uint32_t)len )
         return -E2BIG;
@@ -509,6 +535,8 @@ int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void) 
buf, unsigned long len)
      * watchdog timeout.
      */
     watchdog_disable();
+
+    saved_nmi_callback = set_nmi_callback(microcode_nmi_callback);
     /*
      * Late loading dance. Why the heavy-handed stop_machine effort?
      *
@@ -521,6 +549,7 @@ int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void) 
buf, unsigned long len)
      *   conservative and good.
      */
     ret = stop_machine_run(do_microcode_update, patch, NR_CPUS);
+    set_nmi_callback(saved_nmi_callback);
     watchdog_enable();
 
     updated = atomic_read(&cpu_updated);
-- 
1.8.3.1


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel