[v6 0/2] virtio-gpu: fix error handling and improve consistency

[v6 0/2] virtio-gpu: fix error handling and improve consistency

[Honglei Huang]

This series addresses error handling issues in virtio-gpu and improves
code consistency across the virtio-gpu subsystem.

The first patch fixes a critical bug in virgl_cmd_resource_create_blob()
where an inverted error check causes the function to fail when it should
succeed. This is a standalone bug fix that should be backported.

The second patch improves code consistency by unifying the error checking
style for virtio_gpu_create_mapping_iov() in if-statement contexts across
virtio-gpu files, following the preferred QEMU coding convention.

Changes since v5:
- Reverted changes to virtio-gpu-rutabaga.c to keep CHECK macro usage
  consistent with other error checks in the same file
- Updated patch 2 commit message to clarify that CHECK macro patterns
  in rutabaga.c are intentionally left unchanged

Changes since v4:
- Split the single patch into two separate patches for better clarity
- Separated the critical bug fix from the style consistency improvements
- The bug fix (patch 1) can now be easily identified and backported
- The consistency improvements (patch 2) are clearly marked as cleanup

Changes since v3:
- Extended consistency improvements to virtio-gpu-rutabaga.c
- Changed CHECK(!ret) to CHECK(ret >= 0) and CHECK(!result) to
  CHECK(result >= 0) in rutabaga functions for consistency
- Now covers all virtio-gpu files that use virtio_gpu_create_mapping_iov()

Changes since v2:
- Use 'if (ret < 0)' instead of 'if (ret != 0)' following maintainer's
  feedback on preferred QEMU coding style for error checking functions
  that return 0 on success and negative on error
- Updated all similar usages across virtio-gpu files for consistency
- Expanded scope from single function fix to codebase-wide style consistency

Honglei Huang (2):
  virtio-gpu: fix error handling in virgl_cmd_resource_create_blob
  virtio-gpu: use consistent error checking for
    virtio_gpu_create_mapping_iov

 hw/display/virtio-gpu-virgl.c | 4 ++--
 hw/display/virtio-gpu.c       | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

-- 
2.34.1

[v6 1/2] virtio-gpu: fix error handling in virgl_cmd_resource_create_blob

[Honglei Huang]

Fix inverted error check in virgl_cmd_resource_create_blob() that causes
the function to return error when virtio_gpu_create_mapping_iov() succeeds.

virtio_gpu_create_mapping_iov() returns 0 on success and negative values
on error. The check 'if (!ret)' incorrectly treats success (ret=0) as an
error condition, causing the function to fail when it should succeed.

Change the condition to 'if (ret != 0)' to properly detect errors.

Fixes: 7c092f17ccee ("virtio-gpu: Handle resource blob commands")
Signed-off-by: Honglei Huang <honghuan@amd.com>
Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 hw/display/virtio-gpu-virgl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c
index 94ddc01f91..e60e1059df 100644
--- a/hw/display/virtio-gpu-virgl.c
+++ b/hw/display/virtio-gpu-virgl.c
@@ -701,7 +701,7 @@ static void virgl_cmd_resource_create_blob(VirtIOGPU *g,
         ret = virtio_gpu_create_mapping_iov(g, cblob.nr_entries, sizeof(cblob),
                                             cmd, &res->base.addrs,
                                             &res->base.iov, &res->base.iov_cnt);
-        if (!ret) {
+        if (ret != 0) {
             cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
             return;
         }
-- 
2.34.1

[v6 2/2] virtio-gpu: use consistent error checking for virtio_gpu_create_mapping_iov

[Honglei Huang]

Unify error checking style for virtio_gpu_create_mapping_iov() across the
codebase to improve consistency and readability.

virtio_gpu_create_mapping_iov() returns 0 on success and negative values
on error. The original code used inconsistent patterns for checking errors:
- Some used 'if (ret != 0)' in virtio-gpu-virgl.c and virtio-gpu.c
- Some used 'CHECK(!ret, cmd)' in virtio-gpu-rutabaga.c

For if-statement checks, change to 'if (ret < 0)' which is the preferred
QEMU coding convention for functions that return 0 on success and negative
on error. This makes the return value convention immediately clear to code
readers.

For CHECK macro usage in virtio-gpu-rutabaga.c, keep the original
'CHECK(!ret, cmd)' pattern as it is more concise and consistent with other
error checks in the same file.

Updated locations:
- hw/display/virtio-gpu-virgl.c: virgl_resource_attach_backing()
- hw/display/virtio-gpu-virgl.c: virgl_cmd_resource_create_blob()
- hw/display/virtio-gpu.c: virtio_gpu_resource_create_blob()
- hw/display/virtio-gpu.c: virtio_gpu_resource_attach_backing()

Signed-off-by: Honglei Huang <honghuan@amd.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
---
 hw/display/virtio-gpu-virgl.c | 4 ++--
 hw/display/virtio-gpu.c       | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c
index e60e1059df..6ebd9293e5 100644
--- a/hw/display/virtio-gpu-virgl.c
+++ b/hw/display/virtio-gpu-virgl.c
@@ -557,7 +557,7 @@ static void virgl_resource_attach_backing(VirtIOGPU *g,
 
     ret = virtio_gpu_create_mapping_iov(g, att_rb.nr_entries, sizeof(att_rb),
                                         cmd, NULL, &res_iovs, &res_niov);
-    if (ret != 0) {
+    if (ret < 0) {
         cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
         return;
     }
@@ -701,7 +701,7 @@ static void virgl_cmd_resource_create_blob(VirtIOGPU *g,
         ret = virtio_gpu_create_mapping_iov(g, cblob.nr_entries, sizeof(cblob),
                                             cmd, &res->base.addrs,
                                             &res->base.iov, &res->base.iov_cnt);
-        if (ret != 0) {
+        if (ret < 0) {
             cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
             return;
         }
diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
index 0a1a625b0e..1038c6a49f 100644
--- a/hw/display/virtio-gpu.c
+++ b/hw/display/virtio-gpu.c
@@ -352,7 +352,7 @@ static void virtio_gpu_resource_create_blob(VirtIOGPU *g,
     ret = virtio_gpu_create_mapping_iov(g, cblob.nr_entries, sizeof(cblob),
                                         cmd, &res->addrs, &res->iov,
                                         &res->iov_cnt);
-    if (ret != 0) {
+    if (ret < 0) {
         cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
         g_free(res);
         return;
@@ -931,7 +931,7 @@ virtio_gpu_resource_attach_backing(VirtIOGPU *g,
 
     ret = virtio_gpu_create_mapping_iov(g, ab.nr_entries, sizeof(ab), cmd,
                                         &res->addrs, &res->iov, &res->iov_cnt);
-    if (ret != 0) {
+    if (ret < 0) {
         cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
         return;
     }
-- 
2.34.1

Re: [v6 2/2] virtio-gpu: use consistent error checking for virtio_gpu_create_mapping_iov

[Akihiko Odaki]

On 2025/11/26 11:02, Honglei Huang wrote:
> Unify error checking style for virtio_gpu_create_mapping_iov() across the
> codebase to improve consistency and readability.
> 
> virtio_gpu_create_mapping_iov() returns 0 on success and negative values
> on error. The original code used inconsistent patterns for checking errors:
> - Some used 'if (ret != 0)' in virtio-gpu-virgl.c and virtio-gpu.c
> - Some used 'CHECK(!ret, cmd)' in virtio-gpu-rutabaga.c
> 
> For if-statement checks, change to 'if (ret < 0)' which is the preferred
> QEMU coding convention for functions that return 0 on success and negative
> on error. This makes the return value convention immediately clear to code
> readers.
> 
> For CHECK macro usage in virtio-gpu-rutabaga.c, keep the original
> 'CHECK(!ret, cmd)' pattern as it is more concise and consistent with other
> error checks in the same file.
> 
> Updated locations:
> - hw/display/virtio-gpu-virgl.c: virgl_resource_attach_backing()
> - hw/display/virtio-gpu-virgl.c: virgl_cmd_resource_create_blob()
> - hw/display/virtio-gpu.c: virtio_gpu_resource_create_blob()
> - hw/display/virtio-gpu.c: virtio_gpu_resource_attach_backing()
> 
> Signed-off-by: Honglei Huang <honghuan@amd.com>
> Reviewed-by: Markus Armbruster <armbru@redhat.com>

Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>

Re: [v6 2/2] virtio-gpu: use consistent error checking for virtio_gpu_create_mapping_iov

[Dmitry Osipenko]

On 11/26/25 05:02, Honglei Huang wrote:
> Unify error checking style for virtio_gpu_create_mapping_iov() across the
> codebase to improve consistency and readability.
> 
> virtio_gpu_create_mapping_iov() returns 0 on success and negative values
> on error. The original code used inconsistent patterns for checking errors:
> - Some used 'if (ret != 0)' in virtio-gpu-virgl.c and virtio-gpu.c
> - Some used 'CHECK(!ret, cmd)' in virtio-gpu-rutabaga.c
> 
> For if-statement checks, change to 'if (ret < 0)' which is the preferred
> QEMU coding convention for functions that return 0 on success and negative
> on error. This makes the return value convention immediately clear to code
> readers.
> 
> For CHECK macro usage in virtio-gpu-rutabaga.c, keep the original
> 'CHECK(!ret, cmd)' pattern as it is more concise and consistent with other
> error checks in the same file.
> 
> Updated locations:
> - hw/display/virtio-gpu-virgl.c: virgl_resource_attach_backing()
> - hw/display/virtio-gpu-virgl.c: virgl_cmd_resource_create_blob()
> - hw/display/virtio-gpu.c: virtio_gpu_resource_create_blob()
> - hw/display/virtio-gpu.c: virtio_gpu_resource_attach_backing()
> 
> Signed-off-by: Honglei Huang <honghuan@amd.com>
> Reviewed-by: Markus Armbruster <armbru@redhat.com>
> ---
>  hw/display/virtio-gpu-virgl.c | 4 ++--
>  hw/display/virtio-gpu.c       | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c
> index e60e1059df..6ebd9293e5 100644
> --- a/hw/display/virtio-gpu-virgl.c
> +++ b/hw/display/virtio-gpu-virgl.c
> @@ -557,7 +557,7 @@ static void virgl_resource_attach_backing(VirtIOGPU *g,
>  
>      ret = virtio_gpu_create_mapping_iov(g, att_rb.nr_entries, sizeof(att_rb),
>                                          cmd, NULL, &res_iovs, &res_niov);
> -    if (ret != 0) {
> +    if (ret < 0) {
>          cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>          return;
>      }
> @@ -701,7 +701,7 @@ static void virgl_cmd_resource_create_blob(VirtIOGPU *g,
>          ret = virtio_gpu_create_mapping_iov(g, cblob.nr_entries, sizeof(cblob),
>                                              cmd, &res->base.addrs,
>                                              &res->base.iov, &res->base.iov_cnt);
> -        if (ret != 0) {
> +        if (ret < 0) {
>              cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>              return;
>          }
> diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
> index 0a1a625b0e..1038c6a49f 100644
> --- a/hw/display/virtio-gpu.c
> +++ b/hw/display/virtio-gpu.c
> @@ -352,7 +352,7 @@ static void virtio_gpu_resource_create_blob(VirtIOGPU *g,
>      ret = virtio_gpu_create_mapping_iov(g, cblob.nr_entries, sizeof(cblob),
>                                          cmd, &res->addrs, &res->iov,
>                                          &res->iov_cnt);
> -    if (ret != 0) {
> +    if (ret < 0) {
>          cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>          g_free(res);
>          return;
> @@ -931,7 +931,7 @@ virtio_gpu_resource_attach_backing(VirtIOGPU *g,
>  
>      ret = virtio_gpu_create_mapping_iov(g, ab.nr_entries, sizeof(ab), cmd,
>                                          &res->addrs, &res->iov, &res->iov_cnt);
> -    if (ret != 0) {
> +    if (ret < 0) {
>          cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>          return;
>      }

Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

-- 
Best regards,
Dmitry

Re: [v6 2/2] virtio-gpu: use consistent error checking for virtio_gpu_create_mapping_iov

[Honglei Huang]

On 2025/11/26 20:08, Dmitry Osipenko wrote:
> On 11/26/25 05:02, Honglei Huang wrote:
>> Unify error checking style for virtio_gpu_create_mapping_iov() across the
>> codebase to improve consistency and readability.
>>
>> virtio_gpu_create_mapping_iov() returns 0 on success and negative values
>> on error. The original code used inconsistent patterns for checking errors:
>> - Some used 'if (ret != 0)' in virtio-gpu-virgl.c and virtio-gpu.c
>> - Some used 'CHECK(!ret, cmd)' in virtio-gpu-rutabaga.c
>>
>> For if-statement checks, change to 'if (ret < 0)' which is the preferred
>> QEMU coding convention for functions that return 0 on success and negative
>> on error. This makes the return value convention immediately clear to code
>> readers.
>>
>> For CHECK macro usage in virtio-gpu-rutabaga.c, keep the original
>> 'CHECK(!ret, cmd)' pattern as it is more concise and consistent with other
>> error checks in the same file.
>>
>> Updated locations:
>> - hw/display/virtio-gpu-virgl.c: virgl_resource_attach_backing()
>> - hw/display/virtio-gpu-virgl.c: virgl_cmd_resource_create_blob()
>> - hw/display/virtio-gpu.c: virtio_gpu_resource_create_blob()
>> - hw/display/virtio-gpu.c: virtio_gpu_resource_attach_backing()
>>
>> Signed-off-by: Honglei Huang <honghuan@amd.com>
>> Reviewed-by: Markus Armbruster <armbru@redhat.com>
>> ---
>>   hw/display/virtio-gpu-virgl.c | 4 ++--
>>   hw/display/virtio-gpu.c       | 4 ++--
>>   2 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c
>> index e60e1059df..6ebd9293e5 100644
>> --- a/hw/display/virtio-gpu-virgl.c
>> +++ b/hw/display/virtio-gpu-virgl.c
>> @@ -557,7 +557,7 @@ static void virgl_resource_attach_backing(VirtIOGPU *g,
>>   
>>       ret = virtio_gpu_create_mapping_iov(g, att_rb.nr_entries, sizeof(att_rb),
>>                                           cmd, NULL, &res_iovs, &res_niov);
>> -    if (ret != 0) {
>> +    if (ret < 0) {
>>           cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>>           return;
>>       }
>> @@ -701,7 +701,7 @@ static void virgl_cmd_resource_create_blob(VirtIOGPU *g,
>>           ret = virtio_gpu_create_mapping_iov(g, cblob.nr_entries, sizeof(cblob),
>>                                               cmd, &res->base.addrs,
>>                                               &res->base.iov, &res->base.iov_cnt);
>> -        if (ret != 0) {
>> +        if (ret < 0) {
>>               cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>>               return;
>>           }
>> diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
>> index 0a1a625b0e..1038c6a49f 100644
>> --- a/hw/display/virtio-gpu.c
>> +++ b/hw/display/virtio-gpu.c
>> @@ -352,7 +352,7 @@ static void virtio_gpu_resource_create_blob(VirtIOGPU *g,
>>       ret = virtio_gpu_create_mapping_iov(g, cblob.nr_entries, sizeof(cblob),
>>                                           cmd, &res->addrs, &res->iov,
>>                                           &res->iov_cnt);
>> -    if (ret != 0) {
>> +    if (ret < 0) {
>>           cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>>           g_free(res);
>>           return;
>> @@ -931,7 +931,7 @@ virtio_gpu_resource_attach_backing(VirtIOGPU *g,
>>   
>>       ret = virtio_gpu_create_mapping_iov(g, ab.nr_entries, sizeof(ab), cmd,
>>                                           &res->addrs, &res->iov, &res->iov_cnt);
>> -    if (ret != 0) {
>> +    if (ret < 0) {
>>           cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>>           return;
>>       }
> 
> Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> 

Really thanks for the review and patience.

Regards,
Honglei

Re: [v6 2/2] virtio-gpu: use consistent error checking for virtio_gpu_create_mapping_iov

[Dmitry Osipenko]

On 11/27/25 05:55, Honglei Huang wrote:
> 
> 
> On 2025/11/26 20:08, Dmitry Osipenko wrote:
>> On 11/26/25 05:02, Honglei Huang wrote:
>>> Unify error checking style for virtio_gpu_create_mapping_iov() across
>>> the
>>> codebase to improve consistency and readability.
>>>
>>> virtio_gpu_create_mapping_iov() returns 0 on success and negative values
>>> on error. The original code used inconsistent patterns for checking
>>> errors:
>>> - Some used 'if (ret != 0)' in virtio-gpu-virgl.c and virtio-gpu.c
>>> - Some used 'CHECK(!ret, cmd)' in virtio-gpu-rutabaga.c
>>>
>>> For if-statement checks, change to 'if (ret < 0)' which is the preferred
>>> QEMU coding convention for functions that return 0 on success and
>>> negative
>>> on error. This makes the return value convention immediately clear to
>>> code
>>> readers.
>>>
>>> For CHECK macro usage in virtio-gpu-rutabaga.c, keep the original
>>> 'CHECK(!ret, cmd)' pattern as it is more concise and consistent with
>>> other
>>> error checks in the same file.
>>>
>>> Updated locations:
>>> - hw/display/virtio-gpu-virgl.c: virgl_resource_attach_backing()
>>> - hw/display/virtio-gpu-virgl.c: virgl_cmd_resource_create_blob()
>>> - hw/display/virtio-gpu.c: virtio_gpu_resource_create_blob()
>>> - hw/display/virtio-gpu.c: virtio_gpu_resource_attach_backing()
>>>
>>> Signed-off-by: Honglei Huang <honghuan@amd.com>
>>> Reviewed-by: Markus Armbruster <armbru@redhat.com>
>>> ---
>>>   hw/display/virtio-gpu-virgl.c | 4 ++--
>>>   hw/display/virtio-gpu.c       | 4 ++--
>>>   2 files changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-
>>> virgl.c
>>> index e60e1059df..6ebd9293e5 100644
>>> --- a/hw/display/virtio-gpu-virgl.c
>>> +++ b/hw/display/virtio-gpu-virgl.c
>>> @@ -557,7 +557,7 @@ static void
>>> virgl_resource_attach_backing(VirtIOGPU *g,
>>>         ret = virtio_gpu_create_mapping_iov(g, att_rb.nr_entries,
>>> sizeof(att_rb),
>>>                                           cmd, NULL, &res_iovs,
>>> &res_niov);
>>> -    if (ret != 0) {
>>> +    if (ret < 0) {
>>>           cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>>>           return;
>>>       }
>>> @@ -701,7 +701,7 @@ static void
>>> virgl_cmd_resource_create_blob(VirtIOGPU *g,
>>>           ret = virtio_gpu_create_mapping_iov(g, cblob.nr_entries,
>>> sizeof(cblob),
>>>                                               cmd, &res->base.addrs,
>>>                                               &res->base.iov, &res-
>>> >base.iov_cnt);
>>> -        if (ret != 0) {
>>> +        if (ret < 0) {
>>>               cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>>>               return;
>>>           }
>>> diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
>>> index 0a1a625b0e..1038c6a49f 100644
>>> --- a/hw/display/virtio-gpu.c
>>> +++ b/hw/display/virtio-gpu.c
>>> @@ -352,7 +352,7 @@ static void
>>> virtio_gpu_resource_create_blob(VirtIOGPU *g,
>>>       ret = virtio_gpu_create_mapping_iov(g, cblob.nr_entries,
>>> sizeof(cblob),
>>>                                           cmd, &res->addrs, &res->iov,
>>>                                           &res->iov_cnt);
>>> -    if (ret != 0) {
>>> +    if (ret < 0) {
>>>           cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>>>           g_free(res);
>>>           return;
>>> @@ -931,7 +931,7 @@ virtio_gpu_resource_attach_backing(VirtIOGPU *g,
>>>         ret = virtio_gpu_create_mapping_iov(g, ab.nr_entries,
>>> sizeof(ab), cmd,
>>>                                           &res->addrs, &res->iov,
>>> &res->iov_cnt);
>>> -    if (ret != 0) {
>>> +    if (ret < 0) {
>>>           cmd->error = VIRTIO_GPU_RESP_ERR_UNSPEC;
>>>           return;
>>>       }
>>
>> Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
>>
> 
> Really thanks for the review and patience.

There is a last word from Alex here, though likely the current version
will be good to him, Thanks for the contribution.

-- 
Best regards,
Dmitry