[dpdk-stable] [dpdk-dev] [PATCH] vhost: fix packed ring defines declaration

[Maxime Coquelin]

On 11/22/18 8:20 PM, Ferruh Yigit wrote:
> On 11/22/2018 6:51 PM, Maxime Coquelin wrote:
>>
>>
>> On 11/22/18 7:23 PM, Ferruh Yigit wrote:
>>> On 11/22/2018 5:09 PM, Maxime Coquelin wrote:
>>>> The packed ring defines were declared only if kernel
>>>> header does not declare them.
>>>> The problem is that they are not applied in upstream kernel,
>>>> and some changes in the names have been required.
>>>>
>>>> This patch declares the defines unconditionally, which
>>>> fixes potential build issues.
>>>
>>> +1 to address possible build issues.
>>>
>>>>
>>>> Fixes: 297b1e7350f6 ("vhost: add virtio packed virtqueue defines")
>>>> Cc: stable at dpdk.org
>>>>
>>>> Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
>>>> ---
>>>>    lib/librte_vhost/vhost.h | 22 +++++++++++-----------
>>>>    1 file changed, 11 insertions(+), 11 deletions(-)
>>>>
>>>> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
>>>> index 760f42192..5218f1b12 100644
>>>> --- a/lib/librte_vhost/vhost.h
>>>> +++ b/lib/librte_vhost/vhost.h
>>>> @@ -219,13 +219,6 @@ struct vhost_msg {
>>>>    
>>>>    #define VIRTIO_F_RING_PACKED 34
>>>>    
>>>> -#define VRING_DESC_F_NEXT	1
>>>> -#define VRING_DESC_F_WRITE	2
>>>> -#define VRING_DESC_F_INDIRECT	4
>>>
>>> Why these are not re-defined below? Not used?
>>
>> These defines are in kernel headers since the beginning of virtio
>> support, so there are no reasons to keep them (and they aren't packed-
>> ring specific).
>>
>> I can let them if you prefer, it does not hurt but shouldn't be here.
> 
> Not required, I just want to confirm nothing missed.
> 
>>
>>>> -
>>>> -#define VRING_DESC_F_AVAIL	(1ULL << 7)
>>>> -#define VRING_DESC_F_USED	(1ULL << 15)
>>>> -
>>>>    struct vring_packed_desc {
>>>>    	uint64_t addr;
>>>>    	uint32_t len;
>>>> @@ -233,16 +226,23 @@ struct vring_packed_desc {
>>>>    	uint16_t flags;
>>>>    };
>>>>    
>>>> -#define VRING_EVENT_F_ENABLE 0x0
>>>> -#define VRING_EVENT_F_DISABLE 0x1
>>>> -#define VRING_EVENT_F_DESC 0x2
>>>> -
>>>>    struct vring_packed_desc_event {
>>>>    	uint16_t off_wrap;
>>>>    	uint16_t flags;
>>>>    };
>>>>    #endif
>>>>    
>>>> +/*
>>>> + * Declare below packed ring defines unconditionally
>>>> + * as Kernel header might use different names.
>>>> + */
>>>> +#define VRING_DESC_F_AVAIL	(1ULL << 7)
>>>> +#define VRING_DESC_F_USED	(1ULL << 15)
>>>> +
>>>> +#define VRING_EVENT_F_ENABLE 0x0
>>>> +#define VRING_EVENT_F_DISABLE 0x1
>>>> +#define VRING_EVENT_F_DESC 0x2
>>>
>>> What if Linux changes mind and uses old names again, build will fail again. If
>>> related part in Linux is not released yet, what do you think being on safe side
>>> and adding these defines with "#ifndef" wrap?
>>
>> There are the "old" ones.
>> In any case it will work (I tested it).
> 
> I see they are the old ones but is there any chance that kernel uses them again
> (for some odd reason) ? Which can break the build. Should we add a protection?

Yes, there is a chance, but that would not break build, it will just
override it.

> 
>>
>> In a future release, I plan to get rid of this dependency with Kernel
>> which only causes problems.
>>
>> There was a benefit at the beginning when all needed declarations where
>> in the Kernel headers. But now, every time we add a new virtio feature,
>> we have to check kernel supports it and if not define it.
>>
>> Thanks,
>> Maxime
>>>> +
>>>>    /*
>>>>     * Available and used descs are in same order
>>>>     */
>>>>
>>>
>