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    SubjectRe: [PATCH RFC 8/8] xen/arm,arm64: enable SWIOTLB_XEN
    On Wed, Jul 31, 2013 at 06:45:32PM +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.
    >
    > 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@eu.citrix.com>
    > ---
    > 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 | 118 +++++++++++++++++++++++++++++++++++++++
    > arch/arm64/Kconfig | 1 +
    > arch/arm64/xen/Makefile | 2 +-
    > drivers/xen/Kconfig | 1 -
    > drivers/xen/swiotlb-xen.c | 18 ++++++
    > 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 05125ab..72b53b9 100644
    > --- a/arch/arm/Kconfig
    > +++ b/arch/arm/Kconfig
    > @@ -1849,6 +1849,7 @@ 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..4ba1add
    > --- /dev/null
    > +++ b/arch/arm/xen/mm.c
    > @@ -0,0 +1,118 @@
    > +#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;
    > +}

    Could this code be made out to be more generic? It is almost the same on
    x86 - it just a different hypercall.
    > +
    > +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, i;
    > +
    > + /* 2. Get a new contiguous memory extent. */

    Step 1) is missing.

    > + 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;
    > +

    Ahem! Stray white-space
    > + return success ? 0 : -ENOMEM;
    > +}
    > +EXPORT_SYMBOL_GPL(xen_create_contiguous_region);
    > +
    > +void xen_destroy_contiguous_region(unsigned long vstart, unsigned int order)
    > +{
    > + int i;
    > + 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);
    > +
    > + 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 c79ac88..4ae6cf6 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)
    > +#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{
    > dma_addr_t dma_addr;
    > phys_addr_t phys_addr;
    > --
    > 1.7.2.5
    >


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