[Qemu-devel] [RFC PATCH] cputlb: modernise the debug support

[Qemu-devel] [RFC PATCH] cputlb: modernise the debug support

[Alex Bennée]

To avoid cluttering the code with #ifdef legs we wrap up the print
statements into a tlb_debug() macro. As access to the virtual TLB can
get quite heavy defining DEBUG_TLB_LOG will ensure all the logs go to
the qemu_log target of CPU_LOG_MMU instead of stderr.

I've also removed DEBUG_TLB_CHECK which wasn't used.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 cputlb.c | 47 ++++++++++++++++++++++++++++-------------------
 1 file changed, 28 insertions(+), 19 deletions(-)

diff --git a/cputlb.c b/cputlb.c
index 7606548..ddb7b59 100644
--- a/cputlb.c
+++ b/cputlb.c
@@ -30,8 +30,23 @@
 #include "exec/ram_addr.h"
 #include "tcg/tcg.h"
 
-//#define DEBUG_TLB
-//#define DEBUG_TLB_CHECK
+/* DEBUG defines, enable DEBUG_TLB_LOG to log to the CPU_LOG_MMU target */
+/* #define DEBUG_TLB */
+/* #define DEBUG_TLB_LOG */
+
+#ifdef DEBUG_TLB
+#ifdef DEBUG_TLB_LOG
+#define tlb_debug(fmt, ...) do {                                        \
+        qemu_log_mask(CPU_LOG_MMU, "%s: " fmt, __func__, ## __VA_ARGS__); \
+    } while (0)
+#else
+#define tlb_debug(fmt, ...) do {                               \
+        fprintf(stderr, "%s: " fmt, __func__, ## __VA_ARGS__); \
+    } while (0)
+#endif
+#else
+#define tlb_debug(fmt, ...) do { } while (0)
+#endif
 
 /* statistics */
 int tlb_flush_count;
@@ -52,9 +67,8 @@ void tlb_flush(CPUState *cpu, int flush_global)
 {
     CPUArchState *env = cpu->env_ptr;
 
-#if defined(DEBUG_TLB)
-    printf("tlb_flush:\n");
-#endif
+    tlb_debug("global: %d\n", flush_global);
+
     /* must reset current TB so that interrupts cannot modify the
        links while we are modifying them */
     cpu->current_tb = NULL;
@@ -87,16 +101,14 @@ void tlb_flush_page(CPUState *cpu, target_ulong addr)
     int i;
     int mmu_idx;
 
-#if defined(DEBUG_TLB)
-    printf("tlb_flush_page: " TARGET_FMT_lx "\n", addr);
-#endif
+    tlb_debug("page :" TARGET_FMT_lx "\n", addr);
+
     /* Check if we need to flush due to large pages.  */
     if ((addr & env->tlb_flush_mask) == env->tlb_flush_addr) {
-#if defined(DEBUG_TLB)
-        printf("tlb_flush_page: forced full flush ("
-               TARGET_FMT_lx "/" TARGET_FMT_lx ")\n",
-               env->tlb_flush_addr, env->tlb_flush_mask);
-#endif
+        tlb_debug("forcing full flush ("
+                  TARGET_FMT_lx "/" TARGET_FMT_lx ")\n",
+                  env->tlb_flush_addr, env->tlb_flush_mask);
+
         tlb_flush(cpu, 1);
         return;
     }
@@ -272,12 +284,9 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong vaddr,
     section = address_space_translate_for_iotlb(cpu, paddr, &xlat, &sz);
     assert(sz >= TARGET_PAGE_SIZE);
 
-#if defined(DEBUG_TLB)
-    qemu_log_mask(CPU_LOG_MMU,
-           "tlb_set_page: vaddr=" TARGET_FMT_lx " paddr=0x" TARGET_FMT_plx
-           " prot=%x idx=%d\n",
-           vaddr, paddr, prot, mmu_idx);
-#endif
+    tlb_debug("tlb_set_page: vaddr=" TARGET_FMT_lx " paddr=0x" TARGET_FMT_plx
+              " prot=%x idx=%d\n",
+              vaddr, paddr, prot, mmu_idx);
 
     address = vaddr;
     if (!memory_region_is_ram(section->mr) && !memory_region_is_romd(section->mr)) {
-- 
2.4.2

Re: [Qemu-devel] [RFC PATCH] cputlb: modernise the debug support

[Eric Blake]

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On 06/05/2015 09:55 AM, Alex Bennée wrote:
> To avoid cluttering the code with #ifdef legs we wrap up the print
> statements into a tlb_debug() macro. As access to the virtual TLB can
> get quite heavy defining DEBUG_TLB_LOG will ensure all the logs go to
> the qemu_log target of CPU_LOG_MMU instead of stderr.
> 
> I've also removed DEBUG_TLB_CHECK which wasn't used.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>  cputlb.c | 47 ++++++++++++++++++++++++++++-------------------
>  1 file changed, 28 insertions(+), 19 deletions(-)
> 
> diff --git a/cputlb.c b/cputlb.c
> index 7606548..ddb7b59 100644
> --- a/cputlb.c
> +++ b/cputlb.c
> @@ -30,8 +30,23 @@
>  #include "exec/ram_addr.h"
>  #include "tcg/tcg.h"
>  
> -//#define DEBUG_TLB
> -//#define DEBUG_TLB_CHECK
> +/* DEBUG defines, enable DEBUG_TLB_LOG to log to the CPU_LOG_MMU target */
> +/* #define DEBUG_TLB */
> +/* #define DEBUG_TLB_LOG */
> +
> +#ifdef DEBUG_TLB
> +#ifdef DEBUG_TLB_LOG
> +#define tlb_debug(fmt, ...) do {                                        \
> +        qemu_log_mask(CPU_LOG_MMU, "%s: " fmt, __func__, ## __VA_ARGS__); \
> +    } while (0)
> +#else
> +#define tlb_debug(fmt, ...) do {                               \
> +        fprintf(stderr, "%s: " fmt, __func__, ## __VA_ARGS__); \
> +    } while (0)
> +#endif
> +#else
> +#define tlb_debug(fmt, ...) do { } while (0)

This is prone to bitrot.

Better would be:

#ifdef DEBUG_TLB
# define DEBUG_TLB_GATE 1
# ifdef DEBUG_TLB_LOG
#  define DEBUG_TLB_LOG_GATE 1
# else
#  define DEBUG_TLB_LOG_GATE 0
# endif
#else
# define DEBUG_TLB_GATE 0
# define DEBUG_TLB_LOG_GATE 0
#endif

#define tlb_debug(fmt, ...) do { \
    if (DEBUG_TLB_LOG_GATE) { \
        qemu_log_mask(CPU_LOG_MMU, "%s: " fmt, __func__, \
                      ## __VA_ARGS__); \
    } else if (DEBUG_TLB_GATE) { \
        fprintf(stderr, "%s: " fmt, __func__, ## __VA_ARGS__); \
    } \
} while (0)

because then tlb_debug() will automatically guarantee compiler
compliance to correct fmt vs. argument, while still benefitting from no
increase in code size (all compilers can properly optimize if(0) blocks).

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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