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

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Date:   Mon, 21 May 2018 08:44:40 +0300
From:   Oleksandr Andrushchenko <andr2000@...il.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-media@...r.kernel.org,
        jgross@...e.com, konrad.wilk@...cle.com
Cc:     daniel.vetter@...el.com, dongwon.kim@...el.com,
        matthew.d.roper@...el.com,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
Subject: Re: [Xen-devel][RFC 2/3] xen/grant-table: Extend API to work with DMA
 buffers

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@...m.com>
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
>> ---
>>   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);