[Xen-changelog] [xen stable-4.8] xen/arm: Add performance counters in guest atomic helpers

[patchbot@xxxxxxx]

commit 514de954078700bd3091e6f95115ca4fabbee4d1
Author:     Julien Grall <julien.grall@xxxxxxx>
AuthorDate: Mon Apr 29 15:05:29 2019 +0100
Commit:     Julien Grall <julien.grall@xxxxxxx>
CommitDate: Fri Jun 14 15:46:00 2019 +0100

    xen/arm: Add performance counters in guest atomic helpers
    
    Add performance counters in guest atomic helpers to be able to detect
    whether a guest is often paused during the operations.
    
    This is part of XSA-295.
    
    Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
    Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/include/asm-arm/guest_atomics.h | 12 ++++++++++++
 xen/include/asm-arm/perfc_defn.h    |  3 +++
 2 files changed, 15 insertions(+)

diff --git a/xen/include/asm-arm/guest_atomics.h 
b/xen/include/asm-arm/guest_atomics.h
index 61925d313d..698508bf87 100644
--- a/xen/include/asm-arm/guest_atomics.h
+++ b/xen/include/asm-arm/guest_atomics.h
@@ -24,9 +24,13 @@ DECLARE_PER_CPU(unsigned int, guest_safe_atomic_max);
 #define guest_bitop(name)                                                   \
 static inline void guest_##name(struct domain *d, int nr, volatile void *p) \
 {                                                                           \
+    perfc_incr(atomics_guest);                                              \
+                                                                            \
     if ( name##_timeout(nr, p, this_cpu(guest_safe_atomic_max)) )           \
         return;                                                             \
                                                                             \
+    perfc_incr(atomics_guest_paused);                                       \
+                                                                            \
     domain_pause_nosync(d);                                                 \
     name(nr, p);                                                            \
     domain_unpause(d);                                                      \
@@ -38,11 +42,15 @@ static inline int guest_##name(struct domain *d, int nr, 
volatile void *p)  \
     bool succeed;                                                           \
     int oldbit;                                                             \
                                                                             \
+    perfc_incr(atomics_guest);                                              \
+                                                                            \
     succeed = name##_timeout(nr, p, &oldbit,                                \
                              this_cpu(guest_safe_atomic_max));              \
     if ( succeed )                                                          \
         return oldbit;                                                      \
                                                                             \
+    perfc_incr(atomics_guest_paused);                                       \
+                                                                            \
     domain_pause_nosync(d);                                                 \
     oldbit = name(nr, p);                                                   \
     domain_unpause(d);                                                      \
@@ -73,10 +81,14 @@ static inline unsigned long __guest_cmpxchg(struct domain 
*d,
 {
     unsigned long oldval = old;
 
+    perfc_incr(atomics_guest);
+
     if ( __cmpxchg_mb_timeout(ptr, &oldval, new, size,
                               this_cpu(guest_safe_atomic_max)) )
         return oldval;
 
+    perfc_incr(atomics_guest_paused);
+
     domain_pause_nosync(d);
     oldval = __cmpxchg_mb(ptr, old, new, size);
     domain_unpause(d);
diff --git a/xen/include/asm-arm/perfc_defn.h b/xen/include/asm-arm/perfc_defn.h
index 69fabe7529..987fe7f86a 100644
--- a/xen/include/asm-arm/perfc_defn.h
+++ b/xen/include/asm-arm/perfc_defn.h
@@ -71,6 +71,9 @@ PERFCOUNTER(phys_timer_irqs,  "Physical timer interrupts")
 PERFCOUNTER(virt_timer_irqs,  "Virtual timer interrupts")
 PERFCOUNTER(maintenance_irqs, "Maintenance interrupts")
 
+PERFCOUNTER(atomics_guest,    "atomics: guest access")
+PERFCOUNTER(atomics_guest_paused,   "atomics: guest paused")
+
 /*#endif*/ /* __XEN_PERFC_DEFN_H__ */
 
 /*
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.8

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