Re: [dpdk-dev] [PATCH v2 2/3] vfio: fix DMA mapping granularity for type1 iova as va

[Nithin Dabilpuram <nithind1988@gmail.com>]

On Tue, Nov 10, 2020 at 02:17:39PM +0000, Burakov, Anatoly wrote:
> On 05-Nov-20 9:04 AM, Nithin Dabilpuram wrote:
> > Partial unmapping is not supported for VFIO IOMMU type1
> > by kernel. Though kernel gives return as zero, the unmapped size
> > returned will not be same as expected. So check for
> > returned unmap size and return error.
> > 
> > For IOVA as PA, DMA mapping is already at memseg size
> > granularity. Do the same even for IOVA as VA mode as
> > DMA map/unmap triggered by heap allocations,
> > maintain granularity of memseg page size so that heap
> > expansion and contraction does not have this issue.
> > 
> > For user requested DMA map/unmap disallow partial unmapping
> > for VFIO type1.
> > 
> > Fixes: 73a639085938 ("vfio: allow to map other memory regions")
> > Cc: anatoly.burakov@intel.com
> > Cc: stable@dpdk.org
> > 
> > Signed-off-by: Nithin Dabilpuram <ndabilpuram@marvell.com>
> > ---
> 
> <snip>
> 
> > @@ -525,12 +528,19 @@ vfio_mem_event_callback(enum rte_mem_event type, const void *addr, size_t len,
> >   	/* for IOVA as VA mode, no need to care for IOVA addresses */
> >   	if (rte_eal_iova_mode() == RTE_IOVA_VA && msl->external == 0) {
> >   		uint64_t vfio_va = (uint64_t)(uintptr_t)addr;
> > -		if (type == RTE_MEM_EVENT_ALLOC)
> > -			vfio_dma_mem_map(default_vfio_cfg, vfio_va, vfio_va,
> > -					len, 1);
> > -		else
> > -			vfio_dma_mem_map(default_vfio_cfg, vfio_va, vfio_va,
> > -					len, 0);
> > +		uint64_t page_sz = msl->page_sz;
> > +
> > +		/* Maintain granularity of DMA map/unmap to memseg size */
> > +		for (; cur_len < len; cur_len += page_sz) {
> > +			if (type == RTE_MEM_EVENT_ALLOC)
> > +				vfio_dma_mem_map(default_vfio_cfg, vfio_va,
> > +						 vfio_va, page_sz, 1);
> > +			else
> > +				vfio_dma_mem_map(default_vfio_cfg, vfio_va,
> > +						 vfio_va, page_sz, 0);
> 
> I think you're mapping the same address here, over and over. Perhaps you
> meant `vfio_va + cur_len` for the mapping addresses?

There is a 'vfio_va += page_sz;' in next line right ?
> 
> -- 
> Thanks,
> Anatoly