Re: [Xen-devel][RFC 2/3] xen/grant-table: Extend API to work with DMA buffers

[Oleksandr Andrushchenko]

On 05/19/2018 01:19 AM, Boris Ostrovsky wrote:
> On 05/17/2018 04:26 AM, Oleksandr Andrushchenko wrote:
> > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> >
> > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> > ---
> >   drivers/xen/grant-table.c | 49 +++++++++++++++++++++++++++++++++++++++
> >   include/xen/grant_table.h |  7 ++++++
> >   2 files changed, 56 insertions(+)
> >
> > diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> > index bb36b1e1dbcc..c27bcc420575 100644
> > --- a/drivers/xen/grant-table.c
> > +++ b/drivers/xen/grant-table.c
> > @@ -729,6 +729,55 @@ void gnttab_free_pages(int nr_pages, struct page **pages)
> >   }
> >   EXPORT_SYMBOL(gnttab_free_pages);
> >   
> > +int gnttab_dma_alloc_pages(struct device *dev, bool coherent,
> > +			   int nr_pages, struct page **pages,
> > +			   void **vaddr, dma_addr_t *dev_bus_addr)
> > +{
> > +	int i;
> > +	int ret;
> > +
> > +	ret = alloc_dma_xenballooned_pages(dev, coherent, nr_pages, pages,
> > +					   vaddr, dev_bus_addr);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	for (i = 0; i < nr_pages; i++) {
> > +#if BITS_PER_LONG < 64
> > +		struct xen_page_foreign *foreign;
> > +
> > +		foreign = kzalloc(sizeof(*foreign), GFP_KERNEL);
> > +		if (!foreign) {
> > +			gnttab_dma_free_pages(dev, flags, nr_pages, pages,
> > +					      *vaddr, *dev_bus_addr);
> > +			return -ENOMEM;
> > +		}
> > +		set_page_private(pages[i], (unsigned long)foreign);
> > +#endif
> > +		SetPagePrivate(pages[i]);
> > +	}
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(gnttab_dma_alloc_pages);
> > +
> > +void gnttab_dma_free_pages(struct device *dev, bool coherent,
> > +			   int nr_pages, struct page **pages,
> > +			   void *vaddr, dma_addr_t dev_bus_addr)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < nr_pages; i++) {
> > +		if (PagePrivate(pages[i])) {
> > +#if BITS_PER_LONG < 64
> > +			kfree((void *)page_private(pages[i]));
> > +#endif
> > +			ClearPagePrivate(pages[i]);
> > +		}
> > +	}
> > +	free_dma_xenballooned_pages(dev, coherent, nr_pages, pages,
> > +				    vaddr, dev_bus_addr);
> > +}
> > +EXPORT_SYMBOL(gnttab_dma_free_pages);
>
> Given that these routines look almost exactly like their non-dma
> counterparts I wonder whether common code could be factored out.
Yes, this can be done
> -boris
>
>
>
>
> > +
> >   /* Handling of paged out grant targets (GNTST_eagain) */
> >   #define MAX_DELAY 256
> >   static inline void
> > diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
> > index 34b1379f9777..20ee2b5ba965 100644
> > --- a/include/xen/grant_table.h
> > +++ b/include/xen/grant_table.h
> > @@ -195,6 +195,13 @@ void gnttab_free_auto_xlat_frames(void);
> >   int gnttab_alloc_pages(int nr_pages, struct page **pages);
> >   void gnttab_free_pages(int nr_pages, struct page **pages);
> >   
> > +int gnttab_dma_alloc_pages(struct device *dev, bool coherent,
> > +			   int nr_pages, struct page **pages,
> > +			   void **vaddr, dma_addr_t *dev_bus_addr);
> > +void gnttab_dma_free_pages(struct device *dev, bool coherent,
> > +			   int nr_pages, struct page **pages,
> > +			   void *vaddr, dma_addr_t dev_bus_addr);
> > +
> >   int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
> >   		    struct gnttab_map_grant_ref *kmap_ops,
> >   		    struct page **pages, unsigned int count);