Re: [dpdk-dev] [PATCH v3 02/10] vdpa/sfc: add support for device initialization

["Xia, Chenbo" <chenbo.xia@intel.com>]

> -----Original Message-----
> From: Vijay Kumar Srivastava <vsrivast@xilinx.com>
> Sent: Tuesday, November 2, 2021 12:38 PM
> To: Xia, Chenbo <chenbo.xia@intel.com>; dev@dpdk.org
> Cc: maxime.coquelin@redhat.com; andrew.rybchenko@oktetlabs.ru; Praveen Kumar
> Jain <praveenj@xilinx.com>
> Subject: RE: [PATCH v3 02/10] vdpa/sfc: add support for device initialization
> 
> Hi Chenbo,
> 
> >-----Original Message-----
> >From: Xia, Chenbo <chenbo.xia@intel.com>
> >Sent: Monday, November 1, 2021 5:19 PM
> >To: Vijay Kumar Srivastava <vsrivast@xilinx.com>; dev@dpdk.org
> >Cc: maxime.coquelin@redhat.com; andrew.rybchenko@oktetlabs.ru; Vijay
> >Kumar Srivastava <vsrivast@xilinx.com>
> >Subject: RE: [PATCH v3 02/10] vdpa/sfc: add support for device initialization
> >
> >Hi Vijay,
> >
> >> -----Original Message-----
> >> From: Vijay Srivastava <vijay.srivastava@xilinx.com>
> >> Sent: Friday, October 29, 2021 10:47 PM
> >> To: dev@dpdk.org
> >> Cc: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>;
> >> andrew.rybchenko@oktetlabs.ru; Vijay Kumar Srivastava
> >> <vsrivast@xilinx.com>
> >> Subject: [PATCH v3 02/10] vdpa/sfc: add support for device
> >> initialization
> >>
> >> From: Vijay Kumar Srivastava <vsrivast@xilinx.com>
> >>
> >> Add HW initialization and vDPA device registration support.
> >>
> >> Signed-off-by: Vijay Kumar Srivastava <vsrivast@xilinx.com>
> >> Acked-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
> >> ---
> [SNIP]
> >> +
> >> +	do {
> >> +		ret = rte_vfio_container_dma_map(sva->vfio_container_fd,
> >> +						 (uint64_t)mz->addr,
> >mcdi_iova,
> >> +						 mcdi_buff_size);
> >> +		if (ret == 0)
> >> +			break;
> >> +
> >> +		mcdi_iova = mcdi_iova >> 1;
> >> +		if (mcdi_iova < mcdi_buff_size)	{
> >> +			sfc_vdpa_err(sva,
> >> +				     "DMA mapping failed for MCDI : %s",
> >> +				     rte_strerror(rte_errno));
> >> +			rte_memzone_free(mz);
> >> +			return ret;
> >> +		}
> >> +
> >> +	} while (ret < 0);
> >
> >So when QEMU iova and mcdi_iova conflicts, you just let vdpa dev failed to
> >configure, right?
> >
> >Why not use re-mapping mcdi dma region as the solution? Any side-effect?
> >Or you just assume conflict can hardly happen?
> 
> MCDI configuration is being done at the very early point of initialization.
> Conflict would be detected later when rte_vhost_get_mem_table() would be
> invoked in .dev_conf callback and
> then MCDI re-mapping can be done in case of conflict,

Agree. It should be done in dev_conf callback.

> for this a patch is in
> progress which would be submitted separately.

OK for me, as the initial version, you can just let dev_conf fail if conflict
happens.

/Chenbo

> 
> Regards,
> Vijay
> 
> [SNIP]