[PATCH-for-4.2 v3 0/3] hw: Remove dynamic field width from trace events

[PATCH-for-4.2 v3 0/3] hw: Remove dynamic field width from trace events

[Philippe Mathieu-Daudé]

Eric noted in [1] the dtrace via stap backend can not support
the dynamic '*' width format.
I'd really like to use dynamic width in trace event because the
read/write accesses are easier to read but it is not a priority.
Since next release is close, time to fix LP#1844817 [2].

Since v2:
- addressed Eric review comments from v2
- improved the documentation

Since v1:
- Do not update the qemu_log_mask() calls in hw/mips/gt64xxx_pci.c

[1] https://lists.gnu.org/archive/html/qemu-devel/2019-09/msg04720.html
[2] https://bugs.launchpad.net/qemu/+bug/1844817

Philippe Mathieu-Daudé (3):
  hw/block/pflash: Remove dynamic field width from trace events
  hw/mips/gt64xxx: Remove dynamic field width from trace events
  trace: Forbid dynamic field width in event format

 docs/devel/tracing.txt        |  3 ++-
 hw/block/pflash_cfi01.c       |  8 ++++----
 hw/block/pflash_cfi02.c       |  8 ++++----
 hw/mips/gt64xxx_pci.c         | 16 ++++++++--------
 hw/block/trace-events         |  8 ++++----
 hw/mips/trace-events          |  4 ++--
 scripts/tracetool/__init__.py |  3 +++
 7 files changed, 27 insertions(+), 23 deletions(-)

-- 
2.21.0

[PATCH-for-4.2 v3 1/3] hw/block/pflash: Remove dynamic field width from trace events

[Philippe Mathieu-Daudé]

Since not all trace backends support dynamic field width in
format (dtrace via stap does not), replace by a static field
width instead.

We previously passed to the trace API 'width << 1' as the number
of hex characters to display (the dynamic field width). We don't
need this anymore. Instead, display the size of bytes accessed.

Reported-by: Eric Blake <eblake@redhat.com>
Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
v3: display size (in byte)

 hw/block/pflash_cfi01.c | 8 ++++----
 hw/block/pflash_cfi02.c | 8 ++++----
 hw/block/trace-events   | 8 ++++----
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
index 566c0acb77..54e6ebd385 100644
--- a/hw/block/pflash_cfi01.c
+++ b/hw/block/pflash_cfi01.c
@@ -276,7 +276,7 @@ static uint32_t pflash_data_read(PFlashCFI01 *pfl, hwaddr offset,
         DPRINTF("BUG in %s\n", __func__);
         abort();
     }
-    trace_pflash_data_read(offset, width << 1, ret);
+    trace_pflash_data_read(offset, width, ret);
     return ret;
 }
 
@@ -389,7 +389,7 @@ static uint32_t pflash_read(PFlashCFI01 *pfl, hwaddr offset,
 
         break;
     }
-    trace_pflash_io_read(offset, width, width << 1, ret, pfl->cmd, pfl->wcycle);
+    trace_pflash_io_read(offset, width, ret, pfl->cmd, pfl->wcycle);
 
     return ret;
 }
@@ -414,7 +414,7 @@ static inline void pflash_data_write(PFlashCFI01 *pfl, hwaddr offset,
 {
     uint8_t *p = pfl->storage;
 
-    trace_pflash_data_write(offset, width << 1, value, pfl->counter);
+    trace_pflash_data_write(offset, width, value, pfl->counter);
     switch (width) {
     case 1:
         p[offset] = value;
@@ -453,7 +453,7 @@ static void pflash_write(PFlashCFI01 *pfl, hwaddr offset,
 
     cmd = value;
 
-    trace_pflash_io_write(offset, width, width << 1, value, pfl->wcycle);
+    trace_pflash_io_write(offset, width, value, pfl->wcycle);
     if (!pfl->wcycle) {
         /* Set the device in I/O access mode */
         memory_region_rom_device_set_romd(&pfl->mem, false);
diff --git a/hw/block/pflash_cfi02.c b/hw/block/pflash_cfi02.c
index 4baca701b7..c7d92c3e79 100644
--- a/hw/block/pflash_cfi02.c
+++ b/hw/block/pflash_cfi02.c
@@ -260,7 +260,7 @@ static uint64_t pflash_data_read(PFlashCFI02 *pfl, hwaddr offset,
 {
     uint8_t *p = (uint8_t *)pfl->storage + offset;
     uint64_t ret = pfl->be ? ldn_be_p(p, width) : ldn_le_p(p, width);
-    trace_pflash_data_read(offset, width << 1, ret);
+    trace_pflash_data_read(offset, width, ret);
     return ret;
 }
 
@@ -385,7 +385,7 @@ static uint64_t pflash_read(void *opaque, hwaddr offset, unsigned int width)
         }
         break;
     }
-    trace_pflash_io_read(offset, width, width << 1, ret, pfl->cmd, pfl->wcycle);
+    trace_pflash_io_read(offset, width, ret, pfl->cmd, pfl->wcycle);
 
     return ret;
 }
@@ -432,7 +432,7 @@ static void pflash_write(void *opaque, hwaddr offset, uint64_t value,
     uint8_t *p;
     uint8_t cmd;
 
-    trace_pflash_io_write(offset, width, width << 1, value, pfl->wcycle);
+    trace_pflash_io_write(offset, width, value, pfl->wcycle);
     cmd = value;
     if (pfl->cmd != 0xA0) {
         /* Reset does nothing during chip erase and sector erase. */
@@ -542,7 +542,7 @@ static void pflash_write(void *opaque, hwaddr offset, uint64_t value,
                 }
                 goto reset_flash;
             }
-            trace_pflash_data_write(offset, width << 1, value, 0);
+            trace_pflash_data_write(offset, width, value, 0);
             if (!pfl->ro) {
                 p = (uint8_t *)pfl->storage + offset;
                 if (pfl->be) {
diff --git a/hw/block/trace-events b/hw/block/trace-events
index 13d1b21dd4..c03e80c2c9 100644
--- a/hw/block/trace-events
+++ b/hw/block/trace-events
@@ -8,10 +8,10 @@ fdc_ioport_write(uint8_t reg, uint8_t value) "write reg 0x%02x val 0x%02x"
 # pflash_cfi01.c
 pflash_reset(void) "reset"
 pflash_timer_expired(uint8_t cmd) "command 0x%02x done"
-pflash_io_read(uint64_t offset, int width, int fmt_width, uint32_t value, uint8_t cmd, uint8_t wcycle) "offset:0x%04"PRIx64" width:%d value:0x%0*x cmd:0x%02x wcycle:%u"
-pflash_io_write(uint64_t offset, int width, int fmt_width, uint32_t value, uint8_t wcycle) "offset:0x%04"PRIx64" width:%d value:0x%0*x wcycle:%u"
-pflash_data_read(uint64_t offset, int width, uint32_t value) "data offset:0x%04"PRIx64" value:0x%0*x"
-pflash_data_write(uint64_t offset, int width, uint32_t value, uint64_t counter) "data offset:0x%04"PRIx64" value:0x%0*x counter:0x%016"PRIx64
+pflash_io_read(uint64_t offset, unsigned size, uint32_t value, uint8_t cmd, uint8_t wcycle) "offset:0x%04"PRIx64" size:%u value:0x%04x cmd:0x%02x wcycle:%u"
+pflash_io_write(uint64_t offset, unsigned size, uint32_t value, uint8_t wcycle) "offset:0x%04"PRIx64" size:%u value:0x%04x wcycle:%u"
+pflash_data_read(uint64_t offset, unsigned size, uint32_t value) "data offset:0x%04"PRIx64" size:%u value:0x%04x"
+pflash_data_write(uint64_t offset, unsigned size, uint32_t value, uint64_t counter) "data offset:0x%04"PRIx64" size:%u value:0x%04x counter:0x%016"PRIx64
 pflash_manufacturer_id(uint16_t id) "Read Manufacturer ID: 0x%04x"
 pflash_device_id(uint16_t id) "Read Device ID: 0x%04x"
 pflash_device_info(uint64_t offset) "Read Device Information offset:0x%04"PRIx64
-- 
2.21.0

Re: [PATCH-for-4.2 v3 1/3] hw/block/pflash: Remove dynamic field width from trace events

[Eric Blake]

On 11/18/19 3:04 PM, Philippe Mathieu-Daudé wrote:
> Since not all trace backends support dynamic field width in
> format (dtrace via stap does not), replace by a static field
> width instead.
> 
> We previously passed to the trace API 'width << 1' as the number
> of hex characters to display (the dynamic field width). We don't
> need this anymore. Instead, display the size of bytes accessed.
> 
> Reported-by: Eric Blake <eblake@redhat.com>
> Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Is it worth a Fixes: XXX calling out the commit that introduced the '*'?

/me goes and searches

Fixes: e8aa2d95ea
Fixes: c1474acd5d

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

Re: [PATCH-for-4.2 v3 1/3] hw/block/pflash: Remove dynamic field width from trace events

[Philippe Mathieu-Daudé]

On 11/18/19 10:15 PM, Eric Blake wrote:
> On 11/18/19 3:04 PM, Philippe Mathieu-Daudé wrote:
>> Since not all trace backends support dynamic field width in
>> format (dtrace via stap does not), replace by a static field
>> width instead.
>>
>> We previously passed to the trace API 'width << 1' as the number
>> of hex characters to display (the dynamic field width). We don't
>> need this anymore. Instead, display the size of bytes accessed.
>>
>> Reported-by: Eric Blake <eblake@redhat.com>
>> Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> 
> Is it worth a Fixes: XXX calling out the commit that introduced the '*'?

Yes, good idea.

> 
> /me goes and searches
> 
> Fixes: e8aa2d95ea
> Fixes: c1474acd5d

Similarly the next patch (hw/mips/gt64xxx_pci.c) fixes ab6bff424f4.

> Reviewed-by: Eric Blake <eblake@redhat.com>

Thanks!

[PATCH-for-4.2 v3 2/3] hw/mips/gt64xxx: Remove dynamic field width from trace events

[Philippe Mathieu-Daudé]

Since not all trace backends support dynamic field width in
format (dtrace via stap does not), replace by a static field
width instead.

We previously passed to the trace API 'width << 1' as the number
of hex characters to display (the dynamic field width). We don't
need this anymore. Instead, display the size of bytes accessed.

Reported-by: Eric Blake <eblake@redhat.com>
Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
v2: Do not update qemu_log_mask()
v3: display size (in byte)
---
 hw/mips/gt64xxx_pci.c | 16 ++++++++--------
 hw/mips/trace-events  |  4 ++--
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/hw/mips/gt64xxx_pci.c b/hw/mips/gt64xxx_pci.c
index 5cab9c1ee1..f1af840d8e 100644
--- a/hw/mips/gt64xxx_pci.c
+++ b/hw/mips/gt64xxx_pci.c
@@ -642,19 +642,19 @@ static void gt64120_writel(void *opaque, hwaddr addr,
         /* not really implemented */
         s->regs[saddr] = ~(~(s->regs[saddr]) | ~(val & 0xfffffffe));
         s->regs[saddr] |= !!(s->regs[saddr] & 0xfffffffe);
-        trace_gt64120_write("INTRCAUSE", size << 1, val);
+        trace_gt64120_write("INTRCAUSE", size, val);
         break;
     case GT_INTRMASK:
         s->regs[saddr] = val & 0x3c3ffffe;
-        trace_gt64120_write("INTRMASK", size << 1, val);
+        trace_gt64120_write("INTRMASK", size, val);
         break;
     case GT_PCI0_ICMASK:
         s->regs[saddr] = val & 0x03fffffe;
-        trace_gt64120_write("ICMASK", size << 1, val);
+        trace_gt64120_write("ICMASK", size, val);
         break;
     case GT_PCI0_SERR0MASK:
         s->regs[saddr] = val & 0x0000003f;
-        trace_gt64120_write("SERR0MASK", size << 1, val);
+        trace_gt64120_write("SERR0MASK", size, val);
         break;
 
     /* Reserved when only PCI_0 is configured. */
@@ -930,19 +930,19 @@ static uint64_t gt64120_readl(void *opaque,
     /* Interrupts */
     case GT_INTRCAUSE:
         val = s->regs[saddr];
-        trace_gt64120_read("INTRCAUSE", size << 1, val);
+        trace_gt64120_read("INTRCAUSE", size, val);
         break;
     case GT_INTRMASK:
         val = s->regs[saddr];
-        trace_gt64120_read("INTRMASK", size << 1, val);
+        trace_gt64120_read("INTRMASK", size, val);
         break;
     case GT_PCI0_ICMASK:
         val = s->regs[saddr];
-        trace_gt64120_read("ICMASK", size << 1, val);
+        trace_gt64120_read("ICMASK", size, val);
         break;
     case GT_PCI0_SERR0MASK:
         val = s->regs[saddr];
-        trace_gt64120_read("SERR0MASK", size << 1, val);
+        trace_gt64120_read("SERR0MASK", size, val);
         break;
 
     /* Reserved when only PCI_0 is configured. */
diff --git a/hw/mips/trace-events b/hw/mips/trace-events
index 75d4c73f2e..321933283f 100644
--- a/hw/mips/trace-events
+++ b/hw/mips/trace-events
@@ -1,4 +1,4 @@
 # gt64xxx.c
-gt64120_read(const char *regname, int width, uint64_t value) "gt64120 read %s value:0x%0*" PRIx64
-gt64120_write(const char *regname, int width, uint64_t value) "gt64120 write %s value:0x%0*" PRIx64
+gt64120_read(const char *regname, unsigned size, uint64_t value) "gt64120 read %s size:%u value:0x%08" PRIx64
+gt64120_write(const char *regname, unsigned size, uint64_t value) "gt64120 write %s size:%u value:0x%08" PRIx64
 gt64120_isd_remap(uint64_t from_length, uint64_t from_addr, uint64_t to_length, uint64_t to_addr) "ISD: 0x%08" PRIx64 "@0x%08" PRIx64 " -> 0x%08" PRIx64 "@0x%08" PRIx64
-- 
2.21.0

Re: [PATCH-for-4.2 v3 2/3] hw/mips/gt64xxx: Remove dynamic field width from trace events

[Eric Blake]

On 11/18/19 3:04 PM, Philippe Mathieu-Daudé wrote:
> Since not all trace backends support dynamic field width in
> format (dtrace via stap does not), replace by a static field
> width instead.
> 
> We previously passed to the trace API 'width << 1' as the number
> of hex characters to display (the dynamic field width). We don't
> need this anymore. Instead, display the size of bytes accessed.
> 
> Reported-by: Eric Blake <eblake@redhat.com>
> Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Fixes: ab6bff424f

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

[PATCH-for-4.2 v3 3/3] trace: Forbid dynamic field width in event format

[Philippe Mathieu-Daudé]

Since not all trace backends support dynamic field width in
format (dtrace via stap does not), forbid them.

Add a check to refuse field width in new formats:

  $ make
  [...]
    GEN     hw/block/trace.h
  Traceback (most recent call last):
    File "scripts/tracetool.py", line 152, in <module>
      main(sys.argv)
    File "scripts/tracetool.py", line 143, in main
      events.extend(tracetool.read_events(fh, arg))
    File "scripts/tracetool/__init__.py", line 371, in read_events
      event = Event.build(line)
    File "scripts/tracetool/__init__.py", line 285, in build
      raise ValueError("Event format must not contain field width '%*'")
  ValueError: Error at hw/block/trace-events:11: Event format must not contain field width '%*'

Reported-by: Eric Blake <eblake@redhat.com>
Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
v3:
- use better regex provided by Eric,
- instead of re.match(), use re.search() which takes unanchored regex,
- added a comment in tracing.txt
---
 docs/devel/tracing.txt        | 3 ++-
 scripts/tracetool/__init__.py | 3 +++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/docs/devel/tracing.txt b/docs/devel/tracing.txt
index 8c0376fefa..6c01ce801e 100644
--- a/docs/devel/tracing.txt
+++ b/docs/devel/tracing.txt
@@ -113,7 +113,8 @@ Format strings should reflect the types defined in the trace event.  Take
 special care to use PRId64 and PRIu64 for int64_t and uint64_t types,
 respectively.  This ensures portability between 32- and 64-bit platforms.
 Format strings must not end with a newline character.  It is the responsibility
-of backends to adapt line ending for proper logging.
+of backends to adapt line ending for proper logging.  Format strings must not
+use numeric field width dynamic precision (SystemTap does not support them).
 
 Each event declaration will start with the event name, then its arguments,
 finally a format string for pretty-printing. For example:
diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py
index 44c118bc2a..ec7fe9fa4a 100644
--- a/scripts/tracetool/__init__.py
+++ b/scripts/tracetool/__init__.py
@@ -206,6 +206,7 @@ class Event(object):
                       "\s*"
                       "(?:(?:(?P<fmt_trans>\".+),)?\s*(?P<fmt>\".+))?"
                       "\s*")
+    _DFWRE = re.compile(r"%[\d\.\- +#']*\*") # dynamic width precision
 
     _VALID_PROPS = set(["disable", "tcg", "tcg-trans", "tcg-exec", "vcpu"])
 
@@ -280,6 +281,8 @@ class Event(object):
         if fmt.endswith(r'\n"'):
             raise ValueError("Event format must not end with a newline "
                              "character")
+        if Event._DFWRE.search(fmt):
+            raise ValueError("Event format must not contain field width '%*'")
 
         if len(fmt_trans) > 0:
             fmt = [fmt_trans, fmt]
-- 
2.21.0

Re: [PATCH-for-4.2 v3 3/3] trace: Forbid dynamic field width in event format

[Eric Blake]

On 11/18/19 3:04 PM, Philippe Mathieu-Daudé wrote:
> Since not all trace backends support dynamic field width in
> format (dtrace via stap does not), forbid them.
> 
> Add a check to refuse field width in new formats:
> 
>    $ make
>    [...]
>      GEN     hw/block/trace.h
>    Traceback (most recent call last):
>      File "scripts/tracetool.py", line 152, in <module>
>        main(sys.argv)
>      File "scripts/tracetool.py", line 143, in main
>        events.extend(tracetool.read_events(fh, arg))
>      File "scripts/tracetool/__init__.py", line 371, in read_events
>        event = Event.build(line)
>      File "scripts/tracetool/__init__.py", line 285, in build
>        raise ValueError("Event format must not contain field width '%*'")
>    ValueError: Error at hw/block/trace-events:11: Event format must not contain field width '%*'
> 
> Reported-by: Eric Blake <eblake@redhat.com>
> Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---

> +++ b/docs/devel/tracing.txt
> @@ -113,7 +113,8 @@ Format strings should reflect the types defined in the trace event.  Take
>   special care to use PRId64 and PRIu64 for int64_t and uint64_t types,
>   respectively.  This ensures portability between 32- and 64-bit platforms.
>   Format strings must not end with a newline character.  It is the responsibility
> -of backends to adapt line ending for proper logging.
> +of backends to adapt line ending for proper logging.  Format strings must not
> +use numeric field width dynamic precision (SystemTap does not support them).

Reads awkwardly - a dynamic precision is not numeric in the format 
string (but '*' instead).  Better might be:

Format strings must not use dynamic field width or precision ('*'), as 
at least SystemTap does not support them.

Or even:

Format strings may use numeric field width or precision, but must not 
use dynamic forms ('*') as at least SystemTap does not support that.

>   
>   Each event declaration will start with the event name, then its arguments,
>   finally a format string for pretty-printing. For example:
> diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py
> index 44c118bc2a..ec7fe9fa4a 100644
> --- a/scripts/tracetool/__init__.py
> +++ b/scripts/tracetool/__init__.py
> @@ -206,6 +206,7 @@ class Event(object):
>                         "\s*"
>                         "(?:(?:(?P<fmt_trans>\".+),)?\s*(?P<fmt>\".+))?"
>                         "\s*")
> +    _DFWRE = re.compile(r"%[\d\.\- +#']*\*") # dynamic width precision

The comment is slightly off - this catches both dynamic field width (any 
'*' before '.') and dynamic precision (any '*' after '.'), maybe the fix 
is just s/width/width or/

>   
>       _VALID_PROPS = set(["disable", "tcg", "tcg-trans", "tcg-exec", "vcpu"])
>   
> @@ -280,6 +281,8 @@ class Event(object):
>           if fmt.endswith(r'\n"'):
>               raise ValueError("Event format must not end with a newline "
>                                "character")
> +        if Event._DFWRE.search(fmt):
> +            raise ValueError("Event format must not contain field width '%*'")

and I don't know if you want to tweak the error message, maybe:
  Event format must not use dynamic '*'

If we're trying to get stuff in 4.2-rc2, patch 1 and 2 are actual bug 
fixes and deserve to go in; patch 3 is nice-to-have but doesn't affect 
the build if it is omitted (as there are no other offenders left), so 
slipping it into 5.0 for a v4 to clean it up slightly doesn't hurt.  I 
don't know who would send the pull request, though, and slipping 1 and 2 
into -rc3 just because of 3 is not ideal.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

Re: [PATCH-for-4.2 v3 3/3] trace: Forbid dynamic field width in event format

[Philippe Mathieu-Daudé]

On 11/18/19 10:26 PM, Eric Blake wrote:
> On 11/18/19 3:04 PM, Philippe Mathieu-Daudé wrote:
>> Since not all trace backends support dynamic field width in
>> format (dtrace via stap does not), forbid them.
>>
>> Add a check to refuse field width in new formats:
>>
>>    $ make
>>    [...]
>>      GEN     hw/block/trace.h
>>    Traceback (most recent call last):
>>      File "scripts/tracetool.py", line 152, in <module>
>>        main(sys.argv)
>>      File "scripts/tracetool.py", line 143, in main
>>        events.extend(tracetool.read_events(fh, arg))
>>      File "scripts/tracetool/__init__.py", line 371, in read_events
>>        event = Event.build(line)
>>      File "scripts/tracetool/__init__.py", line 285, in build
>>        raise ValueError("Event format must not contain field width '%*'")
>>    ValueError: Error at hw/block/trace-events:11: Event format must 
>> not contain field width '%*'
>>
>> Reported-by: Eric Blake <eblake@redhat.com>
>> Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> ---
> 
>> +++ b/docs/devel/tracing.txt
>> @@ -113,7 +113,8 @@ Format strings should reflect the types defined in 
>> the trace event.  Take
>>   special care to use PRId64 and PRIu64 for int64_t and uint64_t types,
>>   respectively.  This ensures portability between 32- and 64-bit 
>> platforms.
>>   Format strings must not end with a newline character.  It is the 
>> responsibility
>> -of backends to adapt line ending for proper logging.
>> +of backends to adapt line ending for proper logging.  Format strings 
>> must not
>> +use numeric field width dynamic precision (SystemTap does not support 
>> them).
> 
> Reads awkwardly - a dynamic precision is not numeric in the format 
> string (but '*' instead).  Better might be:
> 
> Format strings must not use dynamic field width or precision ('*'), as 
> at least SystemTap does not support them.
> 
> Or even:
> 
> Format strings may use numeric field width or precision, but must not 
> use dynamic forms ('*') as at least SystemTap does not support that.
> 
>>   Each event declaration will start with the event name, then its 
>> arguments,
>>   finally a format string for pretty-printing. For example:
>> diff --git a/scripts/tracetool/__init__.py 
>> b/scripts/tracetool/__init__.py
>> index 44c118bc2a..ec7fe9fa4a 100644
>> --- a/scripts/tracetool/__init__.py
>> +++ b/scripts/tracetool/__init__.py
>> @@ -206,6 +206,7 @@ class Event(object):
>>                         "\s*"
>>                         "(?:(?:(?P<fmt_trans>\".+),)?\s*(?P<fmt>\".+))?"
>>                         "\s*")
>> +    _DFWRE = re.compile(r"%[\d\.\- +#']*\*") # dynamic width precision
> 
> The comment is slightly off - this catches both dynamic field width (any 
> '*' before '.') and dynamic precision (any '*' after '.'), maybe the fix 
> is just s/width/width or/
> 
>>       _VALID_PROPS = set(["disable", "tcg", "tcg-trans", "tcg-exec", 
>> "vcpu"])
>> @@ -280,6 +281,8 @@ class Event(object):
>>           if fmt.endswith(r'\n"'):
>>               raise ValueError("Event format must not end with a 
>> newline "
>>                                "character")
>> +        if Event._DFWRE.search(fmt):
>> +            raise ValueError("Event format must not contain field 
>> width '%*'")
> 
> and I don't know if you want to tweak the error message, maybe:
>   Event format must not use dynamic '*'
> 
> If we're trying to get stuff in 4.2-rc2, patch 1 and 2 are actual bug 
> fixes and deserve to go in; patch 3 is nice-to-have but doesn't affect 
> the build if it is omitted (as there are no other offenders left), so 
> slipping it into 5.0 for a v4 to clean it up slightly doesn't hurt.  I 
> don't know who would send the pull request, though, and slipping 1 and 2 
> into -rc3 just because of 3 is not ideal.

Wise thought. I'll respin 1-2 with the Fixes: tag in case qemu-block@ or 
qemu-trivial@ have pending pull-request for tomorrow, they can queue it.
Else they can go via the mips-next tree, since both patch affect the 
Malta board.

Thanks!

Phil.

Re: [PATCH-for-4.2 v3 0/3] hw: Remove dynamic field width from trace events

[Richard Henderson]

On 11/18/19 10:04 PM, Philippe Mathieu-Daudé wrote:
> Philippe Mathieu-Daudé (3):
>   hw/block/pflash: Remove dynamic field width from trace events
>   hw/mips/gt64xxx: Remove dynamic field width from trace events
>   trace: Forbid dynamic field width in event format

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~