From: "Zhu, Lingshan" <lingshan.zhu@intel.com>
To: Jason Wang <jasowang@redhat.com>, mst@redhat.com
Cc: virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [PATCH] vDPA/ifcvf: assign nr_vring to the MSI vector of config_intr by default
Date: Wed, 13 Apr 2022 17:16:06 +0800 [thread overview]
Message-ID: <09a3613f-514b-c769-b8a0-25899b3d3159@intel.com> (raw)
In-Reply-To: <f3f60d6e-a506-bd58-d763-848beb0e4c26@redhat.com>
On 4/13/2022 4:14 PM, Jason Wang wrote:
>
> 在 2022/4/8 下午8:10, Zhu Lingshan 写道:
>> This commit assign struct ifcvf_hw.nr_vring to the MSIX vector of the
>> config interrupt by default in ifcvf_request_config_irq().
>> ifcvf_hw.nr_vring is the most likely and the ideal case for
>> the device config interrupt handling, means every virtqueue has
>> an individual MSIX vector(0 ~ nr_vring - 1), and the config interrupt
>> has
>> its own MSIX vector(number nr_vring).
>>
>> This change can also make GCC W = 2 happy, silence the
>> "uninitialized" warning.
>>
>> Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
>> Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
>> ---
>> drivers/vdpa/ifcvf/ifcvf_main.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c
>> b/drivers/vdpa/ifcvf/ifcvf_main.c
>> index 4366320fb68d..b500fb941dab 100644
>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>> @@ -290,13 +290,13 @@ static int ifcvf_request_config_irq(struct
>> ifcvf_adapter *adapter)
>> struct ifcvf_hw *vf = &adapter->vf;
>> int config_vector, ret;
>> + /* vector 0 ~ vf->nr_vring for vqs, num vf->nr_vring vector
>> for config interrupt */
>
>
> The comment is right before this patch, but probably wrong for
> MSIX_VECTOR_DEV_SHARED.
This comment is for the case when every vq and config interrupt has its
own vector, how
about a better comment "The ideal the default case, vector 0 ~
vf->nr_vring for vqs, num vf->nr_vring vector for config interrupt"
>
>
>> + config_vector = vf->nr_vring;
>> +
>> + /* re-use the vqs vector */
>> if (vf->msix_vector_status == MSIX_VECTOR_DEV_SHARED)
>> return 0;
>> - if (vf->msix_vector_status == MSIX_VECTOR_PER_VQ_AND_CONFIG)
>> - /* vector 0 ~ vf->nr_vring for vqs, num vf->nr_vring vector
>> for config interrupt */
>> - config_vector = vf->nr_vring;
>> -
>> if (vf->msix_vector_status == MSIX_VECTOR_SHARED_VQ_AND_CONFIG)
>> /* vector 0 for vqs and 1 for config interrupt */
>> config_vector = 1;
>
>
> Actually, I prefer to use if ... else ... here.
IMHO, if else may lead to mistakes.
The code:
/* The ideal the default case, vector 0 ~ vf->nr_vring for vqs,
num vf->nr_vring vector for config interrupt */
config_vector = vf->nr_vring;
/* re-use the vqs vector */
if (vf->msix_vector_status == MSIX_VECTOR_DEV_SHARED)
return 0;
if (vf->msix_vector_status == MSIX_VECTOR_SHARED_VQ_AND_CONFIG)
/* vector 0 for vqs and 1 for config interrupt */
config_vector = 1;
here by default config_vector = vf->nr_vring;
If msix_vector_status == MSIX_VECTOR_DEV_SHARED, it will reuse the dev
shared vector, means using the vector(value 0) for data-vqs.
If msix_vector_status == MSIX_VECTOR_SHARED_VQ_AND_CONFIG, it will use
vector=1(vector 0 for data-vqs).
If we use if...else, it will be:
/* re-use the vqs vector */
if (vf->msix_vector_status == MSIX_VECTOR_DEV_SHARED)
return 0;
else
config_vector = 1;
This looks like config_vector can only be 0(re-used vector for the
data-vqs, which is 0) or 1. It shadows the ideal and default case
config_vector = vf->nr_vring
Thanks,
Zhu Lingshan
>
> Thanks
>
>
next prev parent reply other threads:[~2022-04-13 9:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-08 12:10 [PATCH] vDPA/ifcvf: assign nr_vring to the MSI vector of config_intr by default Zhu Lingshan
2022-04-13 8:14 ` Jason Wang
2022-04-13 8:14 ` Jason Wang
2022-04-13 9:16 ` Zhu, Lingshan [this message]
2022-04-15 5:51 ` Jason Wang
2022-04-15 5:51 ` Jason Wang
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