[Xen-devel] [PATCH 10/27] xen: make sure swiotlb allocation is physically contigious

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

When allocating the swiotlb buffer under Xen, make sure the memory is
physically contiguous so that its really suitable for DMA.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/kernel/pci-swiotlb.c |   17 +++++++++++++++--
 drivers/pci/xen-iommu.c       |   16 ++++++++++++++++
 include/xen/swiotlb.h         |   12 ++++++++++++
 3 files changed, 43 insertions(+), 2 deletions(-)
 create mode 100644 include/xen/swiotlb.h

diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index 34f12e9..a7b9410 100644
--- a/arch/x86/kernel/pci-swiotlb.c
+++ b/arch/x86/kernel/pci-swiotlb.c
@@ -11,16 +11,29 @@
 #include <asm/swiotlb.h>
 #include <asm/dma.h>
 
+#include <xen/swiotlb.h>
+#include <asm/xen/hypervisor.h>
+
 int swiotlb __read_mostly;
 
 void * __init swiotlb_alloc_boot(size_t size, unsigned long nslabs)
 {
-       return alloc_bootmem_low_pages(size);
+       void *ret = alloc_bootmem_low_pages(size);
+
+       if (ret && xen_pv_domain())
+               xen_swiotlb_fixup(ret, size, nslabs);
+
+       return ret;
 }
 
 void *swiotlb_alloc(unsigned order, unsigned long nslabs)
 {
-       return (void *)__get_free_pages(GFP_DMA | __GFP_NOWARN, order);
+       void *ret = (void *)__get_free_pages(GFP_DMA | __GFP_NOWARN, order);
+
+       if (ret && xen_pv_domain())
+               xen_swiotlb_fixup(ret, 1u << order, nslabs);
+
+       return ret;
 }
 
 dma_addr_t swiotlb_phys_to_bus(struct device *hwdev, phys_addr_t paddr)
diff --git a/drivers/pci/xen-iommu.c b/drivers/pci/xen-iommu.c
index 5b701e8..dc0da76 100644
--- a/drivers/pci/xen-iommu.c
+++ b/drivers/pci/xen-iommu.c
@@ -12,6 +12,7 @@
 #include <xen/grant_table.h>
 #include <xen/page.h>
 #include <xen/xen-ops.h>
+#include <xen/swiotlb.h>
 
 #include <asm/iommu.h>
 #include <asm/swiotlb.h>
@@ -42,6 +43,21 @@ struct dma_coherent_mem {
        unsigned long   *bitmap;
 };
 
+void xen_swiotlb_fixup(void *buf, size_t size, unsigned long nslabs)
+{
+       unsigned order = get_order(size);
+
+       printk(KERN_DEBUG "xen_swiotlb_fixup: buf=%p size=%zu order=%u\n",
+               buf, size, order);
+
+       if (WARN_ON(size != (PAGE_SIZE << order)))
+               return;
+
+       if (xen_create_contiguous_region((unsigned long)buf,
+                                        order, 0xffffffff))
+               printk(KERN_ERR "xen_create_contiguous_region failed\n");
+}
+
 static inline int address_needs_mapping(struct device *hwdev,
                                                dma_addr_t addr)
 {
diff --git a/include/xen/swiotlb.h b/include/xen/swiotlb.h
new file mode 100644
index 0000000..8d59439
--- /dev/null
+++ b/include/xen/swiotlb.h
@@ -0,0 +1,12 @@
+#ifndef _XEN_SWIOTLB_H
+#define _XEN_SWIOTLB_H
+
+#ifdef CONFIG_PCI_XEN
+extern void xen_swiotlb_fixup(void *buf, size_t size, unsigned long nslabs);
+#else
+static inline void xen_swiotlb_fixup(void *buf, size_t size, unsigned long 
nslabs)
+{
+}
+#endif
+
+#endif /* _XEN_SWIOTLB_H */
-- 
1.6.0.6


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