Re: [PATCH v3 10/10] xen/arm,arm64: enable SWIOTLB_XEN

[Konrad Rzeszutek Wilk]

On Mon, Aug 05, 2013 at 05:30:56PM +0100, Stefano Stabellini wrote:
> Xen on arm and arm64 needs SWIOTLB_XEN: when running on Xen we need to
> program the hardware with mfns rather than pfns for dma addresses.
> Remove SWIOTLB_XEN dependency on X86 and PCI and make XEN select
> SWIOTLB_XEN on arm and arm64.

Should you say something about hardware that has IOMMUs?

> 
> Implement xen_create_contiguous_region on arm and arm64 by using
> XENMEM_get_dma_buf.
> 
> Initialize the xen-swiotlb from xen_early_init (before the native
> dma_ops are initialized), set dma_ops to &xen_swiotlb_dma_ops if we are
> running on Xen.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> 
> 
> Changes in v3:
> - code style changes;
> - warn on XENMEM_put_dma_buf failures.
> ---
>  arch/arm/Kconfig                |    1 +
>  arch/arm/include/asm/xen/page.h |    2 +
>  arch/arm/xen/Makefile           |    2 +-
>  arch/arm/xen/enlighten.c        |    3 +
>  arch/arm/xen/mm.c               |  117 +++++++++++++++++++++++++++++++++++++++
>  arch/arm64/Kconfig              |    1 +
>  arch/arm64/xen/Makefile         |    2 +-
>  drivers/xen/Kconfig             |    1 -
>  drivers/xen/swiotlb-xen.c       |   18 ++++++
>  9 files changed, 144 insertions(+), 3 deletions(-)
>  create mode 100644 arch/arm/xen/mm.c
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index c0bfb33..2c9d112 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1848,6 +1848,7 @@ config XEN
>  	depends on CPU_V7 && !CPU_V6
>  	depends on !GENERIC_ATOMIC64
>  	select ARM_PSCI
> +	select SWIOTLB_XEN
>  	help
>  	  Say Y if you want to run Linux in a Virtual Machine on Xen on ARM.
>  
> diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
> index 359a7b5..b0f7150 100644
> --- a/arch/arm/include/asm/xen/page.h
> +++ b/arch/arm/include/asm/xen/page.h
> @@ -6,12 +6,14 @@
>  
>  #include <linux/pfn.h>
>  #include <linux/types.h>
> +#include <linux/dma-mapping.h>
>  
>  #include <xen/interface/grant_table.h>
>  
>  #define pfn_to_mfn(pfn)			(pfn)
>  #define phys_to_machine_mapping_valid(pfn) (1)
>  #define mfn_to_pfn(mfn)			(mfn)
> +#define mfn_to_local_pfn(m)             (mfn_to_pfn(m))
>  #define mfn_to_virt(m)			(__va(mfn_to_pfn(m) << PAGE_SHIFT))
>  
>  #define pte_mfn	    pte_pfn
> diff --git a/arch/arm/xen/Makefile b/arch/arm/xen/Makefile
> index 4384103..66fc35d 100644
> --- a/arch/arm/xen/Makefile
> +++ b/arch/arm/xen/Makefile
> @@ -1 +1 @@
> -obj-y		:= enlighten.o hypercall.o grant-table.o
> +obj-y		:= enlighten.o hypercall.o grant-table.o mm.o
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 14d17ab..06a6953 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -195,6 +195,7 @@ static void xen_power_off(void)
>   * documentation of the Xen Device Tree format.
>   */
>  #define GRANT_TABLE_PHYSADDR 0
> +extern int xen_mm_init(void);
>  void __init xen_early_init(void)
>  {
>  	struct resource res;
> @@ -230,6 +231,8 @@ void __init xen_early_init(void)
>  		xen_start_info->flags |= SIF_INITDOMAIN|SIF_PRIVILEGED;
>  	else
>  		xen_start_info->flags &= ~(SIF_INITDOMAIN|SIF_PRIVILEGED);
> +
> +	xen_mm_init();
>  }
>  
>  static int __init xen_guest_init(void)
> diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
> new file mode 100644
> index 0000000..de7711a
> --- /dev/null
> +++ b/arch/arm/xen/mm.c
> @@ -0,0 +1,117 @@
> +#include <linux/bootmem.h>
> +#include <linux/gfp.h>
> +#include <linux/export.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/vmalloc.h>
> +#include <linux/swiotlb.h>
> +
> +#include <xen/xen.h>
> +#include <xen/interface/memory.h>
> +#include <xen/swiotlb-xen.h>
> +
> +#include <asm/cacheflush.h>
> +#include <asm/xen/page.h>
> +#include <asm/xen/hypercall.h>
> +#include <asm/xen/interface.h>
> +
> +static int xen_exchange_memory(xen_ulong_t extents_in,
> +			       unsigned int order_in,
> +			       xen_pfn_t *pfns_in,
> +			       xen_ulong_t extents_out,
> +			       unsigned int order_out,
> +			       xen_pfn_t *mfns_out,
> +			       unsigned int address_bits)
> +{
> +	long rc;
> +	int success;
> +
> +	struct xen_memory_exchange exchange = {
> +		.in = {
> +			.nr_extents   = extents_in,
> +			.extent_order = order_in,
> +			.domid        = DOMID_SELF
> +		},
> +		.out = {
> +			.nr_extents   = extents_out,
> +			.extent_order = order_out,
> +			.address_bits = address_bits,
> +			.domid        = DOMID_SELF
> +		}
> +	};
> +	set_xen_guest_handle(exchange.in.extent_start, pfns_in);
> +	set_xen_guest_handle(exchange.out.extent_start, mfns_out);
> +
> +	BUG_ON(extents_in << order_in != extents_out << order_out);
> +
> +
> +	rc = HYPERVISOR_memory_op(XENMEM_get_dma_buf, &exchange);
> +	success = (exchange.nr_exchanged == extents_in);
> +
> +	BUG_ON(!success && ((exchange.nr_exchanged != 0) || (rc == 0)));
> +	BUG_ON(success && (rc != 0));
> +
> +	return success;
> +}
> +
> +int xen_create_contiguous_region(unsigned long vstart, unsigned int order,
> +				 unsigned int address_bits,
> +				 dma_addr_t *dma_handle)
> +{
> +	phys_addr_t pstart = __pa(vstart);
> +	xen_pfn_t in_frame, out_frame;
> +	int success;
> +
> +	/* Get a new contiguous memory extent. */
> +	in_frame = out_frame = pstart >> PAGE_SHIFT;
> +	success = xen_exchange_memory(1, order, &in_frame,
> +				      1, order, &out_frame,
> +				      address_bits);
> +
> +	if (!success)
> +		return -ENOMEM;
> +
> +	*dma_handle = out_frame << PAGE_SHIFT;
> +
> +	return success ? 0 : -ENOMEM;
> +}
> +EXPORT_SYMBOL_GPL(xen_create_contiguous_region);
> +
> +void xen_destroy_contiguous_region(unsigned long vstart, unsigned int order)
> +{
> +	xen_pfn_t in_frame = __pa(vstart) >> PAGE_SHIFT;
> +	struct xen_put_dma_buf buf = {
> +		.in = {
> +			.nr_extents   = 1,
> +			.extent_order = order,
> +			.domid        = DOMID_SELF
> +		},
> +	};
> +	set_xen_guest_handle(buf.in.extent_start, &in_frame);
> +
> +	WARN_ON(HYPERVISOR_memory_op(XENMEM_put_dma_buf, &buf));
> +}
> +EXPORT_SYMBOL_GPL(xen_destroy_contiguous_region);
> +
> +static struct dma_map_ops xen_swiotlb_dma_ops = {
> +	.mapping_error = xen_swiotlb_dma_mapping_error,
> +	.alloc = xen_swiotlb_alloc_coherent,
> +	.free = xen_swiotlb_free_coherent,
> +	.sync_single_for_cpu = xen_swiotlb_sync_single_for_cpu,
> +	.sync_single_for_device = xen_swiotlb_sync_single_for_device,
> +	.sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
> +	.sync_sg_for_device = xen_swiotlb_sync_sg_for_device,
> +	.map_sg = xen_swiotlb_map_sg_attrs,
> +	.unmap_sg = xen_swiotlb_unmap_sg_attrs,
> +	.map_page = xen_swiotlb_map_page,
> +	.unmap_page = xen_swiotlb_unmap_page,
> +	.dma_supported = xen_swiotlb_dma_supported,
> +};
> +
> +int __init xen_mm_init(void)
> +{
> +	xen_swiotlb_init(1, true);
> +	dma_ops = &xen_swiotlb_dma_ops;
> +	return 0;
> +}
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 9737e97..aa1f6fb 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -209,6 +209,7 @@ config XEN_DOM0
>  config XEN
>  	bool "Xen guest support on ARM64 (EXPERIMENTAL)"
>  	depends on ARM64 && OF
> +	select SWIOTLB_XEN
>  	help
>  	  Say Y if you want to run Linux in a Virtual Machine on Xen on ARM64.
>  
> diff --git a/arch/arm64/xen/Makefile b/arch/arm64/xen/Makefile
> index be24040..0ef9637 100644
> --- a/arch/arm64/xen/Makefile
> +++ b/arch/arm64/xen/Makefile
> @@ -1,2 +1,2 @@
> -xen-arm-y	+= $(addprefix ../../arm/xen/, enlighten.o grant-table.o)
> +xen-arm-y	+= $(addprefix ../../arm/xen/, enlighten.o grant-table.o mm.o)
>  obj-y		:= xen-arm.o hypercall.o
> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
> index 9e02d60..7e83688 100644
> --- a/drivers/xen/Kconfig
> +++ b/drivers/xen/Kconfig
> @@ -140,7 +140,6 @@ config XEN_GRANT_DEV_ALLOC
>  
>  config SWIOTLB_XEN
>  	def_bool y
> -	depends on PCI && X86
>  	select SWIOTLB
>  
>  config XEN_TMEM
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 5e9ac83..f166a88 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -59,6 +59,24 @@ static unsigned long xen_io_tlb_nslabs;
>   * Quick lookup value of the bus address of the IOTLB.
>   */
>  
> +#ifndef DMA_ERROR_CODE
> +#define DMA_ERROR_CODE	(~0)

Not zero? And not (-1ULL)?
> +#endif
> +
> +#ifndef CONFIG_X86
> +static unsigned long dma_alloc_coherent_mask(struct device *dev,
> +					    gfp_t gfp)
> +{
> +	unsigned long dma_mask = 0;
> +
> +	dma_mask = dev->coherent_dma_mask;
> +	if (!dma_mask)
> +		dma_mask = (gfp & GFP_DMA) ? DMA_BIT_MASK(24) : DMA_BIT_MASK(32);
> +
> +	return dma_mask;
> +}
> +#endif
> +
>  struct xen_dma_info {
>  	dma_addr_t dma_addr;
>  	phys_addr_t phys_addr;
> -- 
> 1.7.2.5
> 
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