[PATCH 05/15] xen: make it possible to disable tracing in Kconfig.

[Dario Faggioli <dario.faggioli@citrix.com>]

And compile it out of the hypervisor entirely.

Code and other sections' sizes change as follows.

Output of `size`:
      vanilla  patched-Y  patched-N
text  1929007    1929007    1902783
data   337784     337784     337688
bss   1310464    1310464    1310336

Output of `size -A`:
            vanilla  patched-Y  patched-N
.text       1372602    1372602    1348026
.rodata      312152     312152     310680
.init.text   244209     244209     244033
.init.data   224576     224576     224576
.data         57472      57472      57376
.bss        1310464    1310464    1310336
Total      23026516   23027008   22858069

No functional change intended.

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
---
Cc: George Dunlap <George.Dunlap@eu.citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Julien Grall <julien.grall@arm.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Doug Goldstein <cardoe@cardoe.com>
---
 xen/Kconfig.debug             |    8 ++++++++
 xen/arch/x86/hvm/svm/entry.S  |    2 ++
 xen/arch/x86/trace.c          |   23 +++++++++++++++++++++++
 xen/common/trace.c            |   39 +++++++++++++++++++++++++++++++++++----
 xen/drivers/cpufreq/utility.c |    7 +++++--
 xen/include/xen/trace.h       |   30 +++++++++++++++++++++++++++++-
 6 files changed, 102 insertions(+), 7 deletions(-)

diff --git a/xen/Kconfig.debug b/xen/Kconfig.debug
index 689f297..374c1c0 100644
--- a/xen/Kconfig.debug
+++ b/xen/Kconfig.debug
@@ -98,6 +98,14 @@ config PERF_ARRAYS
 	---help---
 	  Enables software performance counter array histograms.
 
+config TRACING
+	bool "Tracing"
+	default y
+	---help---
+	  Enables collecting traces of events occurring in the hypervisor
+	  in per-CPU ring buffers. The 'xentrace' tool can be used to read
+	  the buffers and dump the content on the disk.
+
 
 config VERBOSE_DEBUG
 	bool "Verbose debug messages"
diff --git a/xen/arch/x86/hvm/svm/entry.S b/xen/arch/x86/hvm/svm/entry.S
index a4ab40a..ea4a106 100644
--- a/xen/arch/x86/hvm/svm/entry.S
+++ b/xen/arch/x86/hvm/svm/entry.S
@@ -61,10 +61,12 @@ __UNLIKELY_END(nsvm_hap)
 
         call svm_asid_handle_vmrun
 
+#ifdef CONFIG_TRACING
         cmpb $0,tb_init_done(%rip)
 UNLIKELY_START(nz, svm_trace)
         call svm_trace_vmentry
 UNLIKELY_END(svm_trace)
+#endif
 
         mov  VCPU_svm_vmcb(%rbx),%rcx
         mov  UREGS_rax(%rsp),%rax
diff --git a/xen/arch/x86/trace.c b/xen/arch/x86/trace.c
index 4a953c5..411f798 100644
--- a/xen/arch/x86/trace.c
+++ b/xen/arch/x86/trace.c
@@ -1,3 +1,4 @@
+#ifdef CONFIG_TRACING
 #include <xen/init.h>
 #include <xen/kernel.h>
 #include <xen/lib.h>
@@ -157,3 +158,25 @@ void __trace_ptwr_emulation(unsigned long addr, l1_pgentry_t npte)
         __trace_var(event, 1/*tsc*/, sizeof(d), &d);
     }
 }
+#else /* !CONFIG_TRACING */
+#include <xen/kernel.h>
+#include <xen/trace.h>
+
+void __trace_pv_trap(int trapnr, unsigned long eip,
+                     int use_error_code, unsigned error_code)
+{
+}
+void __trace_pv_page_fault(unsigned long addr, unsigned error_code)
+{
+}
+void __trace_trap_one_addr(unsigned event, unsigned long va)
+{
+}
+void __trace_trap_two_addr(unsigned event, unsigned long va1,
+                           unsigned long va2)
+{
+}
+void __trace_ptwr_emulation(unsigned long addr, l1_pgentry_t npte)
+{
+}
+#endif /* CONFIG_TRACING */
diff --git a/xen/common/trace.c b/xen/common/trace.c
index f29cd4c..2c18462 100644
--- a/xen/common/trace.c
+++ b/xen/common/trace.c
@@ -48,6 +48,11 @@ static unsigned int opt_tevt_mask;
 integer_param("tbuf_size", opt_tbuf_size);
 integer_param("tevt_mask", opt_tevt_mask);
 
+#ifdef CONFIG_TRACING
+/* a flag recording whether initialization has been done */
+/* or more properly, if the tbuf subsystem is enabled right now */
+int tb_init_done __read_mostly;
+
 /* Pointers to the meta-data objects for all system trace buffers */
 static struct t_info *t_info;
 static unsigned int t_info_pages;
@@ -64,10 +69,6 @@ static u32 t_buf_highwater;
 static DEFINE_PER_CPU(unsigned long, lost_records);
 static DEFINE_PER_CPU(unsigned long, lost_records_first_tsc);
 
-/* a flag recording whether initialization has been done */
-/* or more properly, if the tbuf subsystem is enabled right now */
-int tb_init_done __read_mostly;
-
 /* which CPUs tracing is enabled on */
 static cpumask_t tb_cpu_mask;
 
@@ -868,6 +869,36 @@ void __trace_hypercall(uint32_t event, unsigned long op,
 
     __trace_var(event, 1, sizeof(uint32_t) * (1 + (a - d.args)), &d);
 }
+#else /* !CONFIG_TRACING */
+void __init init_trace_bufs(void)
+{
+    opt_tbuf_size = 0;
+}
+
+int tb_control(xen_sysctl_tbuf_op_t *tbc)
+{
+    static DEFINE_SPINLOCK(lock);
+    int rc = 0;
+
+    spin_lock(&lock);
+
+    switch ( tbc->cmd )
+    {
+    case XEN_SYSCTL_TBUFOP_get_info:
+        tbc->evt_mask = 0;
+        tbc->buffer_mfn = 0;
+        tbc->size = 0;
+        break;
+    default:
+        rc = -ENOSYS;
+        break;
+    }
+
+    spin_unlock(&lock);
+
+    return rc;
+}
+#endif /* CONFIG_TRACING */
 
 /*
  * Local variables:
diff --git a/xen/drivers/cpufreq/utility.c b/xen/drivers/cpufreq/utility.c
index 53879fe..b686a9d 100644
--- a/xen/drivers/cpufreq/utility.c
+++ b/xen/drivers/cpufreq/utility.c
@@ -362,11 +362,14 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
 
     if (cpu_online(policy->cpu) && cpufreq_driver->target)
     {
-        unsigned int prev_freq = policy->cur;
+        uint32_t d[2] = { policy->cur, 0 };
 
         retval = cpufreq_driver->target(policy, target_freq, relation);
         if ( retval == 0 )
-            TRACE_2D(TRC_PM_FREQ_CHANGE, prev_freq/1000, policy->cur/1000);
+        {
+            d[1] = policy->cur/1000;
+            trace_var(TRC_PM_FREQ_CHANGE, 1, sizeof(d), d);
+        }
     }
 
     return retval;
diff --git a/xen/include/xen/trace.h b/xen/include/xen/trace.h
index 12966ea..d1b6c70 100644
--- a/xen/include/xen/trace.h
+++ b/xen/include/xen/trace.h
@@ -21,7 +21,11 @@
 #ifndef __XEN_TRACE_H__
 #define __XEN_TRACE_H__
 
+#ifdef CONFIG_TRACING
 extern int tb_init_done;
+#else
+#define tb_init_done 0
+#endif
 
 #include <public/sysctl.h>
 #include <public/trace.h>
@@ -33,6 +37,7 @@ void init_trace_bufs(void);
 /* used to retrieve the physical address of the trace buffers */
 int tb_control(struct xen_sysctl_tbuf_op *tbc);
 
+#ifdef CONFIG_TRACING
 int trace_will_trace_event(u32 event);
 
 void __trace_var(u32 event, bool_t cycles, unsigned int extra, const void *);
@@ -113,7 +118,7 @@ void __trace_hypercall(uint32_t event, unsigned long op,
         }                                                       \
     } while ( 0 )
 
-#define TRACE_6D(_e,d1,d2,d3,d4,d5,d6)                             \
+#define TRACE_6D(_e,d1,d2,d3,d4,d5,d6)                          \
     do {                                                        \
         if ( unlikely(tb_init_done) )                           \
         {                                                       \
@@ -127,5 +132,28 @@ void __trace_hypercall(uint32_t event, unsigned long op,
             __trace_var(_e, 1, sizeof(_d), _d);                 \
         }                                                       \
     } while ( 0 )
+#else /* !CONFIG_TRACING */
+#define trace_will_trace_event(u)     (0)
+static inline void __trace_var(u32 event, bool_t cycles, unsigned int extra,
+                               const void *extra_data)
+{
+}
+static inline void trace_var(u32 event, int cycles, int extra,
+                             const void *extra_data)
+{
+}
+static inline void __trace_hypercall(uint32_t event, unsigned long op,
+                                     const xen_ulong_t *args)
+{
+}
+
+#define TRACE_0D(e)                   do {} while ( 0 )
+#define TRACE_1D(e,d1)                do {} while ( 0 )
+#define TRACE_2D(e,d1,d2)             do {} while ( 0 )
+#define TRACE_3D(e,d1,d2,d3)          do {} while ( 0 )
+#define TRACE_4D(e,d1,d2,d3,d4)       do {} while ( 0 )
+#define TRACE_5D(e,d1,d2,d3,d4,d5)    do {} while ( 0 )
+#define TRACE_6D(e,d1,d2,d3,d4,d5,d6) do {} while ( 0 )
+#endif /* CONFIG_TRACING */
 
 #endif /* __XEN_TRACE_H__ */


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