[PATCH 0/2] hw/block/block.c: improve confusing error

[PATCH 0/2] hw/block/block.c: improve confusing error

[Manos Pitsidianakis]

In cases where a device tries to read more bytes than the block device 
contains with the blk_check_size_and_read_all() function, the error is 
vague: "device requires X bytes, block backend provides Y bytes".

This patch changes the errors of this function to include the block
backend name, the device id and device type name where appropriate.

Manos Pitsidianakis (2):
  hw/core/qdev.c: add qdev_get_human_name()
  hw/block/block.c: improve confusing blk_check_size_and_read_all()
    error

 hw/block/block.c         | 25 +++++++++++++++----------
 hw/block/m25p80.c        |  3 ++-
 hw/block/pflash_cfi01.c  |  4 ++--
 hw/block/pflash_cfi02.c  |  2 +-
 hw/core/qdev.c           | 10 ++++++++++
 include/hw/block/block.h |  4 ++--
 include/hw/qdev-core.h   | 15 +++++++++++++++
 7 files changed, 47 insertions(+), 16 deletions(-)


base-commit: 09be34717190c1620f0c6e5c8765b8da354aeb4b
-- 
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[PATCH 1/2] hw/core/qdev.c: add qdev_get_human_name()

[Manos Pitsidianakis]

Add a simple method to return some kind of human readable identifier for
use in error messages.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
---
 hw/core/qdev.c         | 10 ++++++++++
 include/hw/qdev-core.h | 15 +++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 43d863b0c5..499f191826 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -879,6 +879,16 @@ Object *qdev_get_machine(void)
     return dev;
 }
 
+char *qdev_get_human_name(DeviceState *dev)
+{
+    if (!dev) {
+        return g_strdup("");
+    }
+
+    return dev->id ?
+           g_strdup(dev->id) : object_get_canonical_path(OBJECT(dev));
+}
+
 static MachineInitPhase machine_phase;
 
 bool phase_check(MachineInitPhase phase)
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 151d968238..a8c742b4a3 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -993,6 +993,21 @@ const char *qdev_fw_name(DeviceState *dev);
 void qdev_assert_realized_properly(void);
 Object *qdev_get_machine(void);
 
+/**
+ * qdev_get_human_name() - Return a human-readable name for a device
+ * @dev: The device
+ *
+ * .. note::
+ *    This function is intended for user friendly error messages.
+ *
+ * Returns: A newly allocated string containing the device id if not null,
+ * else the object canonical path if not null. If @dev is NULL, it returns an
+ * allocated empty string.
+ *
+ * Use g_free() to free it.
+ */
+char *qdev_get_human_name(DeviceState *dev);
+
 /* FIXME: make this a link<> */
 bool qdev_set_parent_bus(DeviceState *dev, BusState *bus, Error **errp);
 
-- 
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Re: [PATCH 1/2] hw/core/qdev.c: add qdev_get_human_name()

[Philippe Mathieu-Daudé]

Hi Manos,

On 23/1/24 09:09, Manos Pitsidianakis wrote:
> Add a simple method to return some kind of human readable identifier for
> use in error messages.
> 
> Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
> ---
>   hw/core/qdev.c         | 10 ++++++++++
>   include/hw/qdev-core.h | 15 +++++++++++++++
>   2 files changed, 25 insertions(+)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 43d863b0c5..499f191826 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -879,6 +879,16 @@ Object *qdev_get_machine(void)
>       return dev;
>   }
>   
> +char *qdev_get_human_name(DeviceState *dev)
> +{
> +    if (!dev) {
> +        return g_strdup("");
> +    }
> +
> +    return dev->id ?
> +           g_strdup(dev->id) : object_get_canonical_path(OBJECT(dev));
> +}
> +
>   static MachineInitPhase machine_phase;
>   
>   bool phase_check(MachineInitPhase phase)
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index 151d968238..a8c742b4a3 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -993,6 +993,21 @@ const char *qdev_fw_name(DeviceState *dev);
>   void qdev_assert_realized_properly(void);
>   Object *qdev_get_machine(void);
>   
> +/**
> + * qdev_get_human_name() - Return a human-readable name for a device
> + * @dev: The device
> + *
> + * .. note::
> + *    This function is intended for user friendly error messages.
> + *
> + * Returns: A newly allocated string containing the device id if not null,
> + * else the object canonical path if not null. If @dev is NULL, it returns an
> + * allocated empty string.

In which case do we want to call this with NULL?

> + *
> + * Use g_free() to free it.
> + */
> +char *qdev_get_human_name(DeviceState *dev);
> +
>   /* FIXME: make this a link<> */
>   bool qdev_set_parent_bus(DeviceState *dev, BusState *bus, Error **errp);
>   

Re: [PATCH 1/2] hw/core/qdev.c: add qdev_get_human_name()

[Manos Pitsidianakis]

On Tue, 23 Jan 2024 10:13, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
>Hi Manos,
>
>On 23/1/24 09:09, Manos Pitsidianakis wrote:
>> Add a simple method to return some kind of human readable identifier for
>> use in error messages.
>> 
>> Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
>> ---
>>   hw/core/qdev.c         | 10 ++++++++++
>>   include/hw/qdev-core.h | 15 +++++++++++++++
>>   2 files changed, 25 insertions(+)
>> 
>> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
>> index 43d863b0c5..499f191826 100644
>> --- a/hw/core/qdev.c
>> +++ b/hw/core/qdev.c
>> @@ -879,6 +879,16 @@ Object *qdev_get_machine(void)
>>       return dev;
>>   }
>>   
>> +char *qdev_get_human_name(DeviceState *dev)
>> +{
>> +    if (!dev) {
>> +        return g_strdup("");
>> +    }
>> +
>> +    return dev->id ?
>> +           g_strdup(dev->id) : object_get_canonical_path(OBJECT(dev));
>> +}
>> +
>>   static MachineInitPhase machine_phase;
>>   
>>   bool phase_check(MachineInitPhase phase)
>> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
>> index 151d968238..a8c742b4a3 100644
>> --- a/include/hw/qdev-core.h
>> +++ b/include/hw/qdev-core.h
>> @@ -993,6 +993,21 @@ const char *qdev_fw_name(DeviceState *dev);
>>   void qdev_assert_realized_properly(void);
>>   Object *qdev_get_machine(void);
>>   
>> +/**
>> + * qdev_get_human_name() - Return a human-readable name for a device
>> + * @dev: The device
>> + *
>> + * .. note::
>> + *    This function is intended for user friendly error messages.
>> + *
>> + * Returns: A newly allocated string containing the device id if not null,
>> + * else the object canonical path if not null. If @dev is NULL, it returns an
>> + * allocated empty string.
>
>In which case do we want to call this with NULL?

None I could think of, just future-proofing the NULL case.


>> + *
>> + * Use g_free() to free it.
>> + */
>> +char *qdev_get_human_name(DeviceState *dev);
>> +
>>   /* FIXME: make this a link<> */
>>   bool qdev_set_parent_bus(DeviceState *dev, BusState *bus, Error **errp);
>>   
>

Re: [PATCH 1/2] hw/core/qdev.c: add qdev_get_human_name()

[Philippe Mathieu-Daudé]

On 23/1/24 09:15, Manos Pitsidianakis wrote:
> On Tue, 23 Jan 2024 10:13, Philippe Mathieu-Daudé <philmd@linaro.org> 
> wrote:
>> Hi Manos,
>>
>> On 23/1/24 09:09, Manos Pitsidianakis wrote:
>>> Add a simple method to return some kind of human readable identifier for
>>> use in error messages.
>>>
>>> Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
>>> ---
>>>   hw/core/qdev.c         | 10 ++++++++++
>>>   include/hw/qdev-core.h | 15 +++++++++++++++
>>>   2 files changed, 25 insertions(+)
>>>
>>> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
>>> index 43d863b0c5..499f191826 100644
>>> --- a/hw/core/qdev.c
>>> +++ b/hw/core/qdev.c
>>> @@ -879,6 +879,16 @@ Object *qdev_get_machine(void)
>>>       return dev;
>>>   }
>>> +char *qdev_get_human_name(DeviceState *dev)
>>> +{
>>> +    if (!dev) {
>>> +        return g_strdup("");
>>> +    }
>>> +
>>> +    return dev->id ?
>>> +           g_strdup(dev->id) : object_get_canonical_path(OBJECT(dev));
>>> +}
>>> +
>>>   static MachineInitPhase machine_phase;
>>>   bool phase_check(MachineInitPhase phase)
>>> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
>>> index 151d968238..a8c742b4a3 100644
>>> --- a/include/hw/qdev-core.h
>>> +++ b/include/hw/qdev-core.h
>>> @@ -993,6 +993,21 @@ const char *qdev_fw_name(DeviceState *dev);
>>>   void qdev_assert_realized_properly(void);
>>>   Object *qdev_get_machine(void);
>>> +/**
>>> + * qdev_get_human_name() - Return a human-readable name for a device
>>> + * @dev: The device
>>> + *
>>> + * .. note::
>>> + *    This function is intended for user friendly error messages.
>>> + *
>>> + * Returns: A newly allocated string containing the device id if not 
>>> null,
>>> + * else the object canonical path if not null. If @dev is NULL, it 
>>> returns an
>>> + * allocated empty string.
>>
>> In which case do we want to call this with NULL?
> 
> None I could think of, just future-proofing the NULL case.

I'd rather have a raw assert() as future-proof API, avoiding
dubious corner cases :)

> 
>>> + *
>>> + * Use g_free() to free it.
>>> + */
>>> +char *qdev_get_human_name(DeviceState *dev);
>>> +
>>>   /* FIXME: make this a link<> */
>>>   bool qdev_set_parent_bus(DeviceState *dev, BusState *bus, Error 
>>> **errp);
>>

[PATCH 2/2] hw/block/block.c: improve confusing blk_check_size_and_read_all() error

[Manos Pitsidianakis]

In cases where a device tries to read more bytes than the block device
contains, the error is vague: "device requires X bytes, block backend
provides Y bytes".

This patch changes the errors of this function to include the block
backend name, the device id and device type name where appropriate.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
---
 hw/block/block.c         | 25 +++++++++++++++----------
 hw/block/m25p80.c        |  3 ++-
 hw/block/pflash_cfi01.c  |  4 ++--
 hw/block/pflash_cfi02.c  |  2 +-
 include/hw/block/block.h |  4 ++--
 5 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/hw/block/block.c b/hw/block/block.c
index 9f52ee6e72..624389d62d 100644
--- a/hw/block/block.c
+++ b/hw/block/block.c
@@ -54,29 +54,30 @@ static int blk_pread_nonzeroes(BlockBackend *blk, hwaddr size, void *buf)
  * BDRV_REQUEST_MAX_BYTES.
  * On success, return true.
  * On failure, store an error through @errp and return false.
- * Note that the error messages do not identify the block backend.
- * TODO Since callers don't either, this can result in confusing
- * errors.
+ *
  * This function not intended for actual block devices, which read on
  * demand.  It's for things like memory devices that (ab)use a block
  * backend to provide persistence.
  */
-bool blk_check_size_and_read_all(BlockBackend *blk, void *buf, hwaddr size,
-                                 Error **errp)
+bool blk_check_size_and_read_all(BlockBackend *blk, DeviceState *dev,
+                                 void *buf, hwaddr size, Error **errp)
 {
     int64_t blk_len;
     int ret;
+    g_autofree char *dev_id = NULL;
 
     blk_len = blk_getlength(blk);
     if (blk_len < 0) {
         error_setg_errno(errp, -blk_len,
-                         "can't get size of block backend");
+                         "can't get size of %s block backend", blk_name(blk));
         return false;
     }
     if (blk_len != size) {
-        error_setg(errp, "device requires %" HWADDR_PRIu " bytes, "
-                   "block backend provides %" PRIu64 " bytes",
-                   size, blk_len);
+        dev_id = qdev_get_human_name(dev);
+        error_setg(errp, "%s device with id='%s' requires %" HWADDR_PRIu
+                   " bytes, %s block backend provides %" PRIu64 " bytes",
+                   object_get_typename(OBJECT(dev)), dev_id, size,
+                   blk_name(blk), blk_len);
         return false;
     }
 
@@ -89,7 +90,11 @@ bool blk_check_size_and_read_all(BlockBackend *blk, void *buf, hwaddr size,
     assert(size <= BDRV_REQUEST_MAX_BYTES);
     ret = blk_pread_nonzeroes(blk, size, buf);
     if (ret < 0) {
-        error_setg_errno(errp, -ret, "can't read block backend");
+        dev_id = qdev_get_human_name(dev);
+        error_setg_errno(errp, -ret, "can't read %s block backend"
+                         "for %s device with id='%s'",
+                         blk_name(blk), object_get_typename(OBJECT(dev)),
+                         dev_id);
         return false;
     }
     return true;
diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
index 26ce895628..0a12030a3a 100644
--- a/hw/block/m25p80.c
+++ b/hw/block/m25p80.c
@@ -1617,7 +1617,8 @@ static void m25p80_realize(SSIPeripheral *ss, Error **errp)
         trace_m25p80_binding(s);
         s->storage = blk_blockalign(s->blk, s->size);
 
-        if (!blk_check_size_and_read_all(s->blk, s->storage, s->size, errp)) {
+        if (!blk_check_size_and_read_all(s->blk, DEVICE(s),
+                                         s->storage, s->size, errp)) {
             return;
         }
     } else {
diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
index f956f8bcf7..1bda8424b9 100644
--- a/hw/block/pflash_cfi01.c
+++ b/hw/block/pflash_cfi01.c
@@ -848,8 +848,8 @@ static void pflash_cfi01_realize(DeviceState *dev, Error **errp)
     }
 
     if (pfl->blk) {
-        if (!blk_check_size_and_read_all(pfl->blk, pfl->storage, total_len,
-                                         errp)) {
+        if (!blk_check_size_and_read_all(pfl->blk, dev, pfl->storage,
+                                         total_len, errp)) {
             vmstate_unregister_ram(&pfl->mem, DEVICE(pfl));
             return;
         }
diff --git a/hw/block/pflash_cfi02.c b/hw/block/pflash_cfi02.c
index 6fa56f14c0..2314142373 100644
--- a/hw/block/pflash_cfi02.c
+++ b/hw/block/pflash_cfi02.c
@@ -902,7 +902,7 @@ static void pflash_cfi02_realize(DeviceState *dev, Error **errp)
     }
 
     if (pfl->blk) {
-        if (!blk_check_size_and_read_all(pfl->blk, pfl->storage,
+        if (!blk_check_size_and_read_all(pfl->blk, dev, pfl->storage,
                                          pfl->chip_len, errp)) {
             vmstate_unregister_ram(&pfl->orig_mem, DEVICE(pfl));
             return;
diff --git a/include/hw/block/block.h b/include/hw/block/block.h
index 15fff66435..de3946a5f1 100644
--- a/include/hw/block/block.h
+++ b/include/hw/block/block.h
@@ -88,8 +88,8 @@ static inline unsigned int get_physical_block_exp(BlockConf *conf)
 
 /* Backend access helpers */
 
-bool blk_check_size_and_read_all(BlockBackend *blk, void *buf, hwaddr size,
-                                 Error **errp);
+bool blk_check_size_and_read_all(BlockBackend *blk, DeviceState *dev,
+                                 void *buf, hwaddr size, Error **errp);
 
 /* Configuration helpers */
 
-- 
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Re: [PATCH 2/2] hw/block/block.c: improve confusing blk_check_size_and_read_all() error

[Philippe Mathieu-Daudé]

On 23/1/24 09:09, Manos Pitsidianakis wrote:
> In cases where a device tries to read more bytes than the block device
> contains, the error is vague: "device requires X bytes, block backend
> provides Y bytes".
> 
> This patch changes the errors of this function to include the block
> backend name, the device id and device type name where appropriate.
> 
> Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
> ---
>   hw/block/block.c         | 25 +++++++++++++++----------
>   hw/block/m25p80.c        |  3 ++-
>   hw/block/pflash_cfi01.c  |  4 ++--
>   hw/block/pflash_cfi02.c  |  2 +-
>   include/hw/block/block.h |  4 ++--
>   5 files changed, 22 insertions(+), 16 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>