diff mbox

[v2,4/9] xen/grant-table: Allow allocating buffers suitable for DMA

Message ID 20180601114132.22596-5-andr2000@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Oleksandr Andrushchenko June 1, 2018, 11:41 a.m. UTC
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

Extend grant table module API to allow allocating buffers that can
be used for DMA operations and mapping foreign grant references
on top of those.
The resulting buffer is similar to the one allocated by the balloon
driver in terms that proper memory reservation is made
({increase|decrease}_reservation and VA mappings updated if needed).
This is useful for sharing foreign buffers with HW drivers which
cannot work with scattered buffers provided by the balloon driver,
but require DMAable memory instead.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
 drivers/xen/Kconfig       |  13 +++++
 drivers/xen/grant-table.c | 109 ++++++++++++++++++++++++++++++++++++++
 include/xen/grant_table.h |  18 +++++++
 3 files changed, 140 insertions(+)

Comments

Boris Ostrovsky June 4, 2018, 6:46 p.m. UTC | #1
On 06/01/2018 07:41 AM, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>
> Extend grant table module API to allow allocating buffers that can
> be used for DMA operations and mapping foreign grant references
> on top of those.
> The resulting buffer is similar to the one allocated by the balloon
> driver in terms that proper memory reservation is made
> ({increase|decrease}_reservation and VA mappings updated if needed).
> This is useful for sharing foreign buffers with HW drivers which
> cannot work with scattered buffers provided by the balloon driver,
> but require DMAable memory instead.
>
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> ---
>  drivers/xen/Kconfig       |  13 +++++
>  drivers/xen/grant-table.c | 109 ++++++++++++++++++++++++++++++++++++++
>  include/xen/grant_table.h |  18 +++++++
>  3 files changed, 140 insertions(+)
>
> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
> index e5d0c28372ea..39536ddfbce4 100644
> --- a/drivers/xen/Kconfig
> +++ b/drivers/xen/Kconfig
> @@ -161,6 +161,19 @@ config XEN_GRANT_DEV_ALLOC
>  	  to other domains. This can be used to implement frontend drivers
>  	  or as part of an inter-domain shared memory channel.
>  
> +config XEN_GRANT_DMA_ALLOC
> +	bool "Allow allocating DMA capable buffers with grant reference module"
> +	depends on XEN && HAS_DMA
> +	help
> +	  Extends grant table module API to allow allocating DMA capable
> +	  buffers and mapping foreign grant references on top of it.
> +	  The resulting buffer is similar to one allocated by the balloon
> +	  driver in terms that proper memory reservation is made
> +	  ({increase|decrease}_reservation and VA mappings updated if needed).
> +	  This is useful for sharing foreign buffers with HW drivers which
> +	  cannot work with scattered buffers provided by the balloon driver,
> +	  but require DMAable memory instead.
> +
>  config SWIOTLB_XEN
>  	def_bool y
>  	select SWIOTLB
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index dbb48a89e987..5658e58d9cc6 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -45,6 +45,9 @@
>  #include <linux/workqueue.h>
>  #include <linux/ratelimit.h>
>  #include <linux/moduleparam.h>
> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
> +#include <linux/dma-mapping.h>
> +#endif
>  
>  #include <xen/xen.h>
>  #include <xen/interface/xen.h>
> @@ -57,6 +60,7 @@
>  #ifdef CONFIG_X86
>  #include <asm/xen/cpuid.h>
>  #endif
> +#include <xen/mem-reservation.h>
>  #include <asm/xen/hypercall.h>
>  #include <asm/xen/interface.h>
>  
> @@ -811,6 +815,73 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages)
>  }
>  EXPORT_SYMBOL_GPL(gnttab_alloc_pages);
>  
> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
> +/**
> + * gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping into
> + * @args: arguments to the function
> + */
> +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args)
> +{
> +	unsigned long pfn, start_pfn;
> +	size_t size;
> +	int i, ret;
> +
> +	size = args->nr_pages << PAGE_SHIFT;
> +	if (args->coherent)
> +		args->vaddr = dma_alloc_coherent(args->dev, size,
> +						 &args->dev_bus_addr,
> +						 GFP_KERNEL | __GFP_NOWARN);
> +	else
> +		args->vaddr = dma_alloc_wc(args->dev, size,
> +					   &args->dev_bus_addr,
> +					   GFP_KERNEL | __GFP_NOWARN);
> +	if (!args->vaddr) {
> +		pr_err("Failed to allocate DMA buffer of size %zu\n", size);
> +		return -ENOMEM;
> +	}
> +
> +	start_pfn = __phys_to_pfn(args->dev_bus_addr);
> +	for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages;
> +			pfn++, i++) {
> +		struct page *page = pfn_to_page(pfn);
> +
> +		args->pages[i] = page;
> +		args->frames[i] = xen_page_to_gfn(page);
> +		xenmem_reservation_scrub_page(page);
> +	}
> +
> +	xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages);
> +
> +	ret = xenmem_reservation_decrease(args->nr_pages, args->frames);
> +	if (ret != args->nr_pages) {
> +		pr_err("Failed to decrease reservation for DMA buffer\n");
> +		ret = -EFAULT;
> +		goto fail_free_dma;
> +	}
> +
> +	ret = gnttab_pages_set_private(args->nr_pages, args->pages);
> +	if (ret < 0)
> +		goto fail_clear_private;
> +
> +	return 0;
> +
> +fail_clear_private:
> +	gnttab_pages_clear_private(args->nr_pages, args->pages);
> +fail_free_dma:
> +	xenmem_reservation_increase(args->nr_pages, args->frames);
> +	xenmem_reservation_va_mapping_update(args->nr_pages, args->pages,
> +					     args->frames);
> +	if (args->coherent)
> +		dma_free_coherent(args->dev, size,
> +				  args->vaddr, args->dev_bus_addr);
> +	else
> +		dma_free_wc(args->dev, size,
> +			    args->vaddr, args->dev_bus_addr);
> +	return ret;
> +}


Would it be possible to call gnttab_dma_free_pages() here?


> +EXPORT_SYMBOL_GPL(gnttab_dma_alloc_pages);
> +#endif
> +
>  void gnttab_pages_clear_private(int nr_pages, struct page **pages)
>  {
>  	int i;
> @@ -838,6 +909,44 @@ void gnttab_free_pages(int nr_pages, struct page **pages)
>  }
>  EXPORT_SYMBOL_GPL(gnttab_free_pages);
>  
> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC

I'd move this after (or before) gnttab_dma_alloc_page() to keep both
inside a single ifdef block.

-boris


> +/**
> + * gnttab_dma_free_pages - free DMAable pages
> + * @args: arguments to the function
> + */
> +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args)
> +{
> +	size_t size;
> +	int i, ret;
> +
> +	gnttab_pages_clear_private(args->nr_pages, args->pages);
> +
> +	for (i = 0; i < args->nr_pages; i++)
> +		args->frames[i] = page_to_xen_pfn(args->pages[i]);
> +
> +	ret = xenmem_reservation_increase(args->nr_pages, args->frames);
> +	if (ret != args->nr_pages) {
> +		pr_err("Failed to decrease reservation for DMA buffer\n");
> +		ret = -EFAULT;
> +	} else {
> +		ret = 0;
> +	}
> +
> +	xenmem_reservation_va_mapping_update(args->nr_pages, args->pages,
> +					     args->frames);
> +
> +	size = args->nr_pages << PAGE_SHIFT;
> +	if (args->coherent)
> +		dma_free_coherent(args->dev, size,
> +				  args->vaddr, args->dev_bus_addr);
> +	else
> +		dma_free_wc(args->dev, size,
> +			    args->vaddr, args->dev_bus_addr);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(gnttab_dma_free_pages);
> +#endif
> +
>  /* 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 de03f2542bb7..9bc5bc07d4d3 100644
> --- a/include/xen/grant_table.h
> +++ b/include/xen/grant_table.h
> @@ -198,6 +198,24 @@ 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);
>  
> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
> +struct gnttab_dma_alloc_args {
> +	/* Device for which DMA memory will be/was allocated. */
> +	struct device *dev;
> +	/* If set then DMA buffer is coherent and write-combine otherwise. */
> +	bool coherent;
> +
> +	int nr_pages;
> +	struct page **pages;
> +	xen_pfn_t *frames;
> +	void *vaddr;
> +	dma_addr_t dev_bus_addr;
> +};
> +
> +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args);
> +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args);
> +#endif
> +
>  int gnttab_pages_set_private(int nr_pages, struct page **pages);
>  void gnttab_pages_clear_private(int nr_pages, struct page **pages);
>
Oleksandr Andrushchenko June 6, 2018, 7:51 a.m. UTC | #2
On 06/04/2018 09:46 PM, Boris Ostrovsky wrote:
> On 06/01/2018 07:41 AM, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>
>> Extend grant table module API to allow allocating buffers that can
>> be used for DMA operations and mapping foreign grant references
>> on top of those.
>> The resulting buffer is similar to the one allocated by the balloon
>> driver in terms that proper memory reservation is made
>> ({increase|decrease}_reservation and VA mappings updated if needed).
>> This is useful for sharing foreign buffers with HW drivers which
>> cannot work with scattered buffers provided by the balloon driver,
>> but require DMAable memory instead.
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> ---
>>   drivers/xen/Kconfig       |  13 +++++
>>   drivers/xen/grant-table.c | 109 ++++++++++++++++++++++++++++++++++++++
>>   include/xen/grant_table.h |  18 +++++++
>>   3 files changed, 140 insertions(+)
>>
>> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
>> index e5d0c28372ea..39536ddfbce4 100644
>> --- a/drivers/xen/Kconfig
>> +++ b/drivers/xen/Kconfig
>> @@ -161,6 +161,19 @@ config XEN_GRANT_DEV_ALLOC
>>   	  to other domains. This can be used to implement frontend drivers
>>   	  or as part of an inter-domain shared memory channel.
>>   
>> +config XEN_GRANT_DMA_ALLOC
>> +	bool "Allow allocating DMA capable buffers with grant reference module"
>> +	depends on XEN && HAS_DMA
>> +	help
>> +	  Extends grant table module API to allow allocating DMA capable
>> +	  buffers and mapping foreign grant references on top of it.
>> +	  The resulting buffer is similar to one allocated by the balloon
>> +	  driver in terms that proper memory reservation is made
>> +	  ({increase|decrease}_reservation and VA mappings updated if needed).
>> +	  This is useful for sharing foreign buffers with HW drivers which
>> +	  cannot work with scattered buffers provided by the balloon driver,
>> +	  but require DMAable memory instead.
>> +
>>   config SWIOTLB_XEN
>>   	def_bool y
>>   	select SWIOTLB
>> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
>> index dbb48a89e987..5658e58d9cc6 100644
>> --- a/drivers/xen/grant-table.c
>> +++ b/drivers/xen/grant-table.c
>> @@ -45,6 +45,9 @@
>>   #include <linux/workqueue.h>
>>   #include <linux/ratelimit.h>
>>   #include <linux/moduleparam.h>
>> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
>> +#include <linux/dma-mapping.h>
>> +#endif
>>   
>>   #include <xen/xen.h>
>>   #include <xen/interface/xen.h>
>> @@ -57,6 +60,7 @@
>>   #ifdef CONFIG_X86
>>   #include <asm/xen/cpuid.h>
>>   #endif
>> +#include <xen/mem-reservation.h>
>>   #include <asm/xen/hypercall.h>
>>   #include <asm/xen/interface.h>
>>   
>> @@ -811,6 +815,73 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages)
>>   }
>>   EXPORT_SYMBOL_GPL(gnttab_alloc_pages);
>>   
>> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
>> +/**
>> + * gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping into
>> + * @args: arguments to the function
>> + */
>> +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args)
>> +{
>> +	unsigned long pfn, start_pfn;
>> +	size_t size;
>> +	int i, ret;
>> +
>> +	size = args->nr_pages << PAGE_SHIFT;
>> +	if (args->coherent)
>> +		args->vaddr = dma_alloc_coherent(args->dev, size,
>> +						 &args->dev_bus_addr,
>> +						 GFP_KERNEL | __GFP_NOWARN);
>> +	else
>> +		args->vaddr = dma_alloc_wc(args->dev, size,
>> +					   &args->dev_bus_addr,
>> +					   GFP_KERNEL | __GFP_NOWARN);
>> +	if (!args->vaddr) {
>> +		pr_err("Failed to allocate DMA buffer of size %zu\n", size);
>> +		return -ENOMEM;
>> +	}
>> +
>> +	start_pfn = __phys_to_pfn(args->dev_bus_addr);
>> +	for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages;
>> +			pfn++, i++) {
>> +		struct page *page = pfn_to_page(pfn);
>> +
>> +		args->pages[i] = page;
>> +		args->frames[i] = xen_page_to_gfn(page);
>> +		xenmem_reservation_scrub_page(page);
>> +	}
>> +
>> +	xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages);
>> +
>> +	ret = xenmem_reservation_decrease(args->nr_pages, args->frames);
>> +	if (ret != args->nr_pages) {
>> +		pr_err("Failed to decrease reservation for DMA buffer\n");
>> +		ret = -EFAULT;
>> +		goto fail_free_dma;
>> +	}
>> +
>> +	ret = gnttab_pages_set_private(args->nr_pages, args->pages);
>> +	if (ret < 0)
>> +		goto fail_clear_private;
>> +
>> +	return 0;
>> +
>> +fail_clear_private:
>> +	gnttab_pages_clear_private(args->nr_pages, args->pages);
>> +fail_free_dma:
>> +	xenmem_reservation_increase(args->nr_pages, args->frames);
>> +	xenmem_reservation_va_mapping_update(args->nr_pages, args->pages,
>> +					     args->frames);
>> +	if (args->coherent)
>> +		dma_free_coherent(args->dev, size,
>> +				  args->vaddr, args->dev_bus_addr);
>> +	else
>> +		dma_free_wc(args->dev, size,
>> +			    args->vaddr, args->dev_bus_addr);
>> +	return ret;
>> +}
>
> Would it be possible to call gnttab_dma_free_pages() here?
As we moved frames array outside - yes, I'll call gnttab_dma_free_pages
on failure then.
>
>> +EXPORT_SYMBOL_GPL(gnttab_dma_alloc_pages);
>> +#endif
>> +
>>   void gnttab_pages_clear_private(int nr_pages, struct page **pages)
>>   {
>>   	int i;
>> @@ -838,6 +909,44 @@ void gnttab_free_pages(int nr_pages, struct page **pages)
>>   }
>>   EXPORT_SYMBOL_GPL(gnttab_free_pages);
>>   
>> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
> I'd move this after (or before) gnttab_dma_alloc_page() to keep both
> inside a single ifdef block.
Ok, will also move and regroup functions to be implemented
close to each other:
gnttab_dma_{alloc|free}_pages
gnttab_{alloc|free}_pages
gnttab_pages_{set|clear}_private
> -boris
>
>
>> +/**
>> + * gnttab_dma_free_pages - free DMAable pages
>> + * @args: arguments to the function
>> + */
>> +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args)
>> +{
>> +	size_t size;
>> +	int i, ret;
>> +
>> +	gnttab_pages_clear_private(args->nr_pages, args->pages);
>> +
>> +	for (i = 0; i < args->nr_pages; i++)
>> +		args->frames[i] = page_to_xen_pfn(args->pages[i]);
>> +
>> +	ret = xenmem_reservation_increase(args->nr_pages, args->frames);
>> +	if (ret != args->nr_pages) {
>> +		pr_err("Failed to decrease reservation for DMA buffer\n");
>> +		ret = -EFAULT;
>> +	} else {
>> +		ret = 0;
>> +	}
>> +
>> +	xenmem_reservation_va_mapping_update(args->nr_pages, args->pages,
>> +					     args->frames);
>> +
>> +	size = args->nr_pages << PAGE_SHIFT;
>> +	if (args->coherent)
>> +		dma_free_coherent(args->dev, size,
>> +				  args->vaddr, args->dev_bus_addr);
>> +	else
>> +		dma_free_wc(args->dev, size,
>> +			    args->vaddr, args->dev_bus_addr);
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(gnttab_dma_free_pages);
>> +#endif
>> +
>>   /* 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 de03f2542bb7..9bc5bc07d4d3 100644
>> --- a/include/xen/grant_table.h
>> +++ b/include/xen/grant_table.h
>> @@ -198,6 +198,24 @@ 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);
>>   
>> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
>> +struct gnttab_dma_alloc_args {
>> +	/* Device for which DMA memory will be/was allocated. */
>> +	struct device *dev;
>> +	/* If set then DMA buffer is coherent and write-combine otherwise. */
>> +	bool coherent;
>> +
>> +	int nr_pages;
>> +	struct page **pages;
>> +	xen_pfn_t *frames;
>> +	void *vaddr;
>> +	dma_addr_t dev_bus_addr;
>> +};
>> +
>> +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args);
>> +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args);
>> +#endif
>> +
>>   int gnttab_pages_set_private(int nr_pages, struct page **pages);
>>   void gnttab_pages_clear_private(int nr_pages, struct page **pages);
>>
diff mbox

Patch

diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index e5d0c28372ea..39536ddfbce4 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -161,6 +161,19 @@  config XEN_GRANT_DEV_ALLOC
 	  to other domains. This can be used to implement frontend drivers
 	  or as part of an inter-domain shared memory channel.
 
+config XEN_GRANT_DMA_ALLOC
+	bool "Allow allocating DMA capable buffers with grant reference module"
+	depends on XEN && HAS_DMA
+	help
+	  Extends grant table module API to allow allocating DMA capable
+	  buffers and mapping foreign grant references on top of it.
+	  The resulting buffer is similar to one allocated by the balloon
+	  driver in terms that proper memory reservation is made
+	  ({increase|decrease}_reservation and VA mappings updated if needed).
+	  This is useful for sharing foreign buffers with HW drivers which
+	  cannot work with scattered buffers provided by the balloon driver,
+	  but require DMAable memory instead.
+
 config SWIOTLB_XEN
 	def_bool y
 	select SWIOTLB
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index dbb48a89e987..5658e58d9cc6 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -45,6 +45,9 @@ 
 #include <linux/workqueue.h>
 #include <linux/ratelimit.h>
 #include <linux/moduleparam.h>
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+#include <linux/dma-mapping.h>
+#endif
 
 #include <xen/xen.h>
 #include <xen/interface/xen.h>
@@ -57,6 +60,7 @@ 
 #ifdef CONFIG_X86
 #include <asm/xen/cpuid.h>
 #endif
+#include <xen/mem-reservation.h>
 #include <asm/xen/hypercall.h>
 #include <asm/xen/interface.h>
 
@@ -811,6 +815,73 @@  int gnttab_alloc_pages(int nr_pages, struct page **pages)
 }
 EXPORT_SYMBOL_GPL(gnttab_alloc_pages);
 
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+/**
+ * gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping into
+ * @args: arguments to the function
+ */
+int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args)
+{
+	unsigned long pfn, start_pfn;
+	size_t size;
+	int i, ret;
+
+	size = args->nr_pages << PAGE_SHIFT;
+	if (args->coherent)
+		args->vaddr = dma_alloc_coherent(args->dev, size,
+						 &args->dev_bus_addr,
+						 GFP_KERNEL | __GFP_NOWARN);
+	else
+		args->vaddr = dma_alloc_wc(args->dev, size,
+					   &args->dev_bus_addr,
+					   GFP_KERNEL | __GFP_NOWARN);
+	if (!args->vaddr) {
+		pr_err("Failed to allocate DMA buffer of size %zu\n", size);
+		return -ENOMEM;
+	}
+
+	start_pfn = __phys_to_pfn(args->dev_bus_addr);
+	for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages;
+			pfn++, i++) {
+		struct page *page = pfn_to_page(pfn);
+
+		args->pages[i] = page;
+		args->frames[i] = xen_page_to_gfn(page);
+		xenmem_reservation_scrub_page(page);
+	}
+
+	xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages);
+
+	ret = xenmem_reservation_decrease(args->nr_pages, args->frames);
+	if (ret != args->nr_pages) {
+		pr_err("Failed to decrease reservation for DMA buffer\n");
+		ret = -EFAULT;
+		goto fail_free_dma;
+	}
+
+	ret = gnttab_pages_set_private(args->nr_pages, args->pages);
+	if (ret < 0)
+		goto fail_clear_private;
+
+	return 0;
+
+fail_clear_private:
+	gnttab_pages_clear_private(args->nr_pages, args->pages);
+fail_free_dma:
+	xenmem_reservation_increase(args->nr_pages, args->frames);
+	xenmem_reservation_va_mapping_update(args->nr_pages, args->pages,
+					     args->frames);
+	if (args->coherent)
+		dma_free_coherent(args->dev, size,
+				  args->vaddr, args->dev_bus_addr);
+	else
+		dma_free_wc(args->dev, size,
+			    args->vaddr, args->dev_bus_addr);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_dma_alloc_pages);
+#endif
+
 void gnttab_pages_clear_private(int nr_pages, struct page **pages)
 {
 	int i;
@@ -838,6 +909,44 @@  void gnttab_free_pages(int nr_pages, struct page **pages)
 }
 EXPORT_SYMBOL_GPL(gnttab_free_pages);
 
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+/**
+ * gnttab_dma_free_pages - free DMAable pages
+ * @args: arguments to the function
+ */
+int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args)
+{
+	size_t size;
+	int i, ret;
+
+	gnttab_pages_clear_private(args->nr_pages, args->pages);
+
+	for (i = 0; i < args->nr_pages; i++)
+		args->frames[i] = page_to_xen_pfn(args->pages[i]);
+
+	ret = xenmem_reservation_increase(args->nr_pages, args->frames);
+	if (ret != args->nr_pages) {
+		pr_err("Failed to decrease reservation for DMA buffer\n");
+		ret = -EFAULT;
+	} else {
+		ret = 0;
+	}
+
+	xenmem_reservation_va_mapping_update(args->nr_pages, args->pages,
+					     args->frames);
+
+	size = args->nr_pages << PAGE_SHIFT;
+	if (args->coherent)
+		dma_free_coherent(args->dev, size,
+				  args->vaddr, args->dev_bus_addr);
+	else
+		dma_free_wc(args->dev, size,
+			    args->vaddr, args->dev_bus_addr);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_dma_free_pages);
+#endif
+
 /* 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 de03f2542bb7..9bc5bc07d4d3 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -198,6 +198,24 @@  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);
 
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+struct gnttab_dma_alloc_args {
+	/* Device for which DMA memory will be/was allocated. */
+	struct device *dev;
+	/* If set then DMA buffer is coherent and write-combine otherwise. */
+	bool coherent;
+
+	int nr_pages;
+	struct page **pages;
+	xen_pfn_t *frames;
+	void *vaddr;
+	dma_addr_t dev_bus_addr;
+};
+
+int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args);
+int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args);
+#endif
+
 int gnttab_pages_set_private(int nr_pages, struct page **pages);
 void gnttab_pages_clear_private(int nr_pages, struct page **pages);