lkml.org 
[lkml]   [2021]   [May]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [Intel-wired-lan] [PATCH][next] virtchnl: Replace one-element array in struct virtchnl_vsi_queue_config_info
From
Date


On 5/28/21 16:56, Nguyen, Anthony L wrote:
> On Tue, 2021-05-25 at 18:16 -0500, Gustavo A. R. Silva wrote:
>> There is a regular need in the kernel to provide a way to declare
>> having a
>> dynamically sized set of trailing elements in a structure. Kernel
>> code
>> should always use “flexible array members”[1] for these cases. The
>> older
>> style of one-element or zero-length arrays should no longer be
>> used[2].
>>
>> Refactor the code according to the use of a flexible-array member in
>> struct
>> virtchnl_vsi_queue_config_info instead of one-element array, and use
>> the
>> flex_array_size() helper.
>>
>> [1] https://en.wikipedia.org/wiki/Flexible_array_member
>> [2]
>> https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
>>
>> Link: https://github.com/KSPP/linux/issues/79
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>> ---
>> include/linux/avf/virtchnl.h | 9 ++++-----
>> 1 file changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/linux/avf/virtchnl.h
>> b/include/linux/avf/virtchnl.h
>> index b554913804bd..ed9c4998f8ac 100644
>> --- a/include/linux/avf/virtchnl.h
>> +++ b/include/linux/avf/virtchnl.h
>> @@ -338,10 +338,10 @@ struct virtchnl_vsi_queue_config_info {
>> u16 vsi_id;
>> u16 num_queue_pairs;
>> u32 pad;
>> - struct virtchnl_queue_pair_info qpair[1];
>> + struct virtchnl_queue_pair_info qpair[];
>> };
>>
>> -VIRTCHNL_CHECK_STRUCT_LEN(72, virtchnl_vsi_queue_config_info);
>> +VIRTCHNL_CHECK_STRUCT_LEN(8, virtchnl_vsi_queue_config_info);
>>
>> /* VIRTCHNL_OP_REQUEST_QUEUES
>> * VF sends this message to request the PF to allocate additional
>> queues to
>> @@ -997,9 +997,8 @@ virtchnl_vc_validate_vf_msg(struct
>> virtchnl_version_info *ver, u32 v_opcode,
>> if (msglen >= valid_len) {
>> struct virtchnl_vsi_queue_config_info *vqc =
>> (struct virtchnl_vsi_queue_config_info
>> *)msg;
>> - valid_len += (vqc->num_queue_pairs *
>> - sizeof(struct
>> - virtchnl_queue_pair_info))
>> ;
>> + valid_len += flex_array_size(vqc, qpair,
>> + vqc-
>>> num_queue_pairs);
>
> The virtchnl file acts as a binary interface between physical and
> virtual functions. There's no guaruntee that the PF and VF will both
> have the newest version. Thus changing this will break compatibility.
> Specifically, the way the size was validated for this op code
> incorrectly expects an extra queue pair structure. Some other
> structures have similar length calculation flaws. We agree that fixing
> this is important, but the fix needs to account that old drivers will
> send an off by 1 size.
>
> To properly handle compatibility we need to introduce a feature flag to
> indicate the new behavior. If the feature flag is not set, we acccept
> messages with the old format (with the extra size). If both the PF and
> VF support the feature flag, we'll use the correct size calculations.
> We're looking to add this and would like to do all the virtchnl
> structure fixes in one series.
>

Oh OK, I see. In this case, I think something like this might work just
fine:

https://git.kernel.org/linus/c0a744dcaa29e9537e8607ae9c965ad936124a4d

What do you think?

Thanks
--
Gustavo

\
 
 \ /
  Last update: 2021-05-29 01:28    [W:0.064 / U:1.488 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site