On Wed, Apr 13, 2022 at 5:16 PM Zhu, Lingshan <lingshan.zhu@xxxxxxxxx> wrote:
>
>
>
> 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@xxxxxxxxx>
> >> Reviewed-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> >> ---
> >> 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"
Actually, I suggest to remove the comment since the code can explain itself.
> >
> >
> >> + 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
I meant something like
if (DEV_SHARED)
return 0;
else if (SHARED_VQ_AND_CONFIG)
config_vector = 1
else if (PER_VQ_AND_CONFIG)
config_vector = vf->nr_vring
else
return -EINVAL;
or using a switch here.
(We get the warning because there's no way for the checker to know
that msix_vector_status must be DEV_SHARED, SHARED_VQ_AND_CONFIG and
PER_VQ_AND_CONFIG).
Thanks
>
> Thanks,
> Zhu Lingshan
>
> >
> > Thanks
> >
> >
>
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