KVM: PPC: Book3S HV: Use bitmap of active threads rather than count

Currently, the entry_exit_count field in the kvmppc_vcore struct
contains two 8-bit counts, one of the threads that have started entering
the guest, and one of the threads that have started exiting the guest.
This changes it to an entry_exit_map field which contains two bitmaps
of 8 bits each.  The advantage of doing this is that it gives us a
bitmap of which threads need to be signalled when exiting the guest.
That means that we no longer need to use the trick of setting the
HDEC to 0 to pull the other threads out of the guest, which led in
some cases to a spurious HDEC interrupt on the next guest entry.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 8 insertions, 7 deletions

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 1517faac9b98..d67a83830bd1 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -263,15 +263,15 @@ struct kvm_arch {
 
 /*
  * Struct for a virtual core.
- * Note: entry_exit_count combines an entry count in the bottom 8 bits
- * and an exit count in the next 8 bits.  This is so that we can
- * atomically increment the entry count iff the exit count is 0
- * without taking the lock.
+ * Note: entry_exit_map combines a bitmap of threads that have entered
+ * in the bottom 8 bits and a bitmap of threads that have exited in the
+ * next 8 bits.  This is so that we can atomically set the entry bit
+ * iff the exit map is 0 without taking a lock.
  */
 struct kvmppc_vcore {
         int n_runnable;
         int num_threads;
-        int entry_exit_count;
+        int entry_exit_map;
         int napping_threads;
         int first_vcpuid;
         u16 pcpu;
@@ -296,8 +296,9 @@ struct kvmppc_vcore {
         ulong conferring_threads;
 };
 
-#define VCORE_ENTRY_COUNT(vc)   ((vc)->entry_exit_count & 0xff)
-#define VCORE_EXIT_COUNT(vc)    ((vc)->entry_exit_count >> 8)
+#define VCORE_ENTRY_MAP(vc)     ((vc)->entry_exit_map & 0xff)
+#define VCORE_EXIT_MAP(vc)      ((vc)->entry_exit_map >> 8)
+#define VCORE_IS_EXITING(vc)    (VCORE_EXIT_MAP(vc) != 0)
 
 /* Values for vcore_state */
 #define VCORE_INACTIVE  0