Re: [PATCH v3] vdpa/ifcvf: fix the calculation of queuepair

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Sep 23, 2022 at 01:43:36PM +0800, Zhu, Lingshan wrote:
> 
> 
> On 9/23/2022 1:32 PM, Michael S. Tsirkin wrote:
> > On Fri, Sep 23, 2022 at 11:21:41AM +0800, Zhu, Lingshan wrote:
> > > 
> > > On 9/23/2022 9:03 AM, Angus Chen wrote:
> > > > The queuepair should be divided by 2 and
> > > > it should not be hw->nr_vring when multi-queue feature was enabled
> > > This is not about MQ, even no MQ, there are still space in the cap storing
> > > (though invalid)queue states that can be addressed.
> > > So I think just describe q_pair_id = qid / 2 here.
> > hmm without MQ qid is always 0 or 1 so the old calculation
> > and the new one give the same result right?
> Yes, if no MQ, the queue pair id is always 0. The original code
> is buggy anyway, we need the queue pair id = qid /2 even without MQ.
> 
> If there are 8 queues, even no MQ feature bit negotiated, the HW
> still stores the queue states though invalid but can be addressed.
> 
> And we are working on a new layout of this LM cap/bar.
> > I guess this is what Angus Chen meant.
> > Would you mind writing a good commit log for us then?
> I think it can be as easy as:
> The q_pair_id to address a queue pair in the lm bar should be
> calculated by queue_id / 2 than queue_id / nr_vring

English requires "rather than" and not "than" here. Otherwise, ok.
Angus Chen could you post v4 with this corrected and Lingshan Zhu's
ack included please?

> Thanks,
> Zhu Lingshan
> > 
> > > for the code change:
> > > Acked-by: Zhu Lingshan<lingshan.zhu@intel.com>
> > > 
> > > Thanks
> > > > Fixes: 2ddae773c93b ("vDPA/ifcvf: detect and use the onboard number of queues directly")
> > > > 
> > > > changes in v2:
> > > >       - add commitid which to be fixed
> > > >       - no code changes
> > > > 
> > > > changes in v3:
> > > >       - updated commit log with more info, addressing comments by MST
> > > >       - no code changes
> > > > 
> > > > Signed-off-by: Angus Chen <angus.chen@jaguarmicro.com>
> > > > ---
> > > >    drivers/vdpa/ifcvf/ifcvf_base.c | 4 ++--
> > > >    1 file changed, 2 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/vdpa/ifcvf/ifcvf_base.c b/drivers/vdpa/ifcvf/ifcvf_base.c
> > > > index 75a703b803a2..3e4486bfa0b7 100644
> > > > --- a/drivers/vdpa/ifcvf/ifcvf_base.c
> > > > +++ b/drivers/vdpa/ifcvf/ifcvf_base.c
> > > > @@ -323,7 +323,7 @@ u16 ifcvf_get_vq_state(struct ifcvf_hw *hw, u16 qid)
> > > >    	u32 q_pair_id;
> > > >    	ifcvf_lm = (struct ifcvf_lm_cfg __iomem *)hw->lm_cfg;
> > > > -	q_pair_id = qid / hw->nr_vring;
> > > > +	q_pair_id = qid / 2;
> > > >    	avail_idx_addr = &ifcvf_lm->vring_lm_cfg[q_pair_id].idx_addr[qid % 2];
> > > >    	last_avail_idx = vp_ioread16(avail_idx_addr);
> > > > @@ -337,7 +337,7 @@ int ifcvf_set_vq_state(struct ifcvf_hw *hw, u16 qid, u16 num)
> > > >    	u32 q_pair_id;
> > > >    	ifcvf_lm = (struct ifcvf_lm_cfg __iomem *)hw->lm_cfg;
> > > > -	q_pair_id = qid / hw->nr_vring;
> > > > +	q_pair_id = qid / 2;
> > > >    	avail_idx_addr = &ifcvf_lm->vring_lm_cfg[q_pair_id].idx_addr[qid % 2];
> > > >    	hw->vring[qid].last_avail_idx = num;
> > > >    	vp_iowrite16(num, avail_idx_addr);

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