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    Subject[PATCH v6 06/19] xen/arm,arm64: enable SWIOTLB_XEN
    Date
    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.

    At the moment always rely on swiotlb-xen, but when Xen starts supporting
    hardware IOMMUs we'll be able to avoid it conditionally on the presence
    of an IOMMU on the platform.

    Implement xen_create_contiguous_region on arm and arm64 by using
    XENMEM_exchange_and_pin.

    Initialize the xen-swiotlb from xen_early_init (before the native
    dma_ops are initialized), set xen_dma_ops to &xen_swiotlb_dma_ops.

    Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>


    Changes in v6:
    - introduce and export xen_dma_ops;
    - call xen_mm_init from as arch_initcall.

    Changes in v4:
    - remove redefinition of DMA_ERROR_CODE;
    - update the code to use XENMEM_exchange_and_pin and XENMEM_unpin;
    - add a note about hardware IOMMU in the commit message.

    Changes in v3:
    - code style changes;
    - warn on XENMEM_put_dma_buf failures.
    ---
    arch/arm/Kconfig | 1 +
    arch/arm/include/asm/xen/hypervisor.h | 2 +
    arch/arm/include/asm/xen/page.h | 2 +
    arch/arm/xen/Makefile | 2 +-
    arch/arm/xen/mm.c | 121 +++++++++++++++++++++++++++++++++
    arch/arm64/Kconfig | 1 +
    arch/arm64/xen/Makefile | 2 +-
    drivers/xen/Kconfig | 1 -
    drivers/xen/swiotlb-xen.c | 16 +++++
    9 files changed, 145 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/hypervisor.h b/arch/arm/include/asm/xen/hypervisor.h
    index d7ab99a..1317ee4 100644
    --- a/arch/arm/include/asm/xen/hypervisor.h
    +++ b/arch/arm/include/asm/xen/hypervisor.h
    @@ -16,4 +16,6 @@ static inline enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
    return PARAVIRT_LAZY_NONE;
    }

    +extern struct dma_map_ops *xen_dma_ops;
    +
    #endif /* _ASM_ARM_XEN_HYPERVISOR_H */
    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/mm.c b/arch/arm/xen/mm.c
    new file mode 100644
    index 0000000..b065c98
    --- /dev/null
    +++ b/arch/arm/xen/mm.c
    @@ -0,0 +1,121 @@
    +#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_exchange_and_pin, &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_unpin unpin = {
    + .in = {
    + .nr_extents = 1,
    + .extent_order = order,
    + .domid = DOMID_SELF
    + },
    + };
    + set_xen_guest_handle(unpin.in.extent_start, &in_frame);
    +
    + WARN_ON(HYPERVISOR_memory_op(XENMEM_unpin, &unpin));
    +}
    +EXPORT_SYMBOL_GPL(xen_destroy_contiguous_region);
    +
    +struct dma_map_ops *xen_dma_ops;
    +EXPORT_SYMBOL_GPL(xen_dma_ops);
    +
    +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, false);
    + xen_dma_ops = &xen_swiotlb_dma_ops;
    + return 0;
    +}
    +arch_initcall(xen_mm_init);
    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 84aef43..a1cb0f4 100644
    --- a/drivers/xen/swiotlb-xen.c
    +++ b/drivers/xen/swiotlb-xen.c
    @@ -45,6 +45,8 @@
    #include <xen/xen-ops.h>
    #include <xen/hvc-console.h>
    #include <xen/features.h>
    +#include <asm/dma-mapping.h>
    +
    /*
    * Used to do a quick range check in swiotlb_tbl_unmap_single and
    * swiotlb_tbl_sync_single_*, to see if the memory was in fact allocated by this
    @@ -58,6 +60,20 @@ static unsigned long xen_io_tlb_nslabs;
    * Quick lookup value of the bus address of the IOTLB.
    */

    +#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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