xen: Add __GFP_DMA flag when xen_swiotlb_init gets free pages on ARM

Stefano Stabellini · David Vrabel · commit 8746515d7f04 · 2015-05-06T15:02:58.000+01:00
Make sure that xen_swiotlb_init allocates buffers that are DMA capable
when at least one memblock is available below 4G. Otherwise we assume
that all devices on the SoC can cope with &gt;4G addresses. We do this on
ARM and ARM64, where dom0 is mapped 1:1, so pfn == mfn in this case.

No functional changes on x86.

From: Chen Baozi &lt;baozich@gmail.com&gt;

Signed-off-by: Chen Baozi &lt;baozich@gmail.com&gt;
Signed-off-by: Stefano Stabellini &lt;stefano.stabellini@eu.citrix.com&gt;
Tested-by: Chen Baozi &lt;baozich@gmail.com&gt;
Acked-by: Konrad Rzeszutek Wilk &lt;konrad.wilk@oracle.com&gt;
Signed-off-by: David Vrabel &lt;david.vrabel@citrix.com&gt;
diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
@@ -110,5 +110,6 @@ static inline bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 bool xen_arch_need_swiotlb(struct device *dev,
 			   unsigned long pfn,
 			   unsigned long mfn);
+unsigned long xen_get_swiotlb_free_pages(unsigned int order);
 
 #endif /* _ASM_ARM_XEN_PAGE_H */
diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
@@ -4,6 +4,7 @@
 #include <linux/gfp.h>
 #include <linux/highmem.h>
 #include <linux/export.h>
+#include <linux/memblock.h>
 #include <linux/of_address.h>
 #include <linux/slab.h>
 #include <linux/types.h>
@@ -21,6 +22,20 @@
 #include <asm/xen/hypercall.h>
 #include <asm/xen/interface.h>
 
+unsigned long xen_get_swiotlb_free_pages(unsigned int order)
+{
+	struct memblock_region *reg;
+	gfp_t flags = __GFP_NOWARN;
+
+	for_each_memblock(memory, reg) {
+		if (reg->base < (phys_addr_t)0xffffffff) {
+			flags |= __GFP_DMA;
+			break;
+		}
+	}
+	return __get_free_pages(flags, order);
+}
+
 enum dma_cache_op {
        DMA_UNMAP,
        DMA_MAP,
diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
@@ -269,4 +269,9 @@ static inline bool xen_arch_need_swiotlb(struct device *dev,
 	return false;
 }
 
+static inline unsigned long xen_get_swiotlb_free_pages(unsigned int order)
+{
+	return __get_free_pages(__GFP_NOWARN, order);
+}
+
 #endif /* _ASM_X86_XEN_PAGE_H */
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
@@ -235,7 +235,7 @@ int __ref xen_swiotlb_init(int verbose, bool early)
 #define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT))
 #define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT)
 		while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
-			xen_io_tlb_start = (void *)__get_free_pages(__GFP_NOWARN, order);
+			xen_io_tlb_start = (void *)xen_get_swiotlb_free_pages(order);
 			if (xen_io_tlb_start)
 				break;
 			order--;

Original file line number	Diff line number	Diff line change
`@@ -269,4 +269,9 @@ static inline bool xen_arch_need_swiotlb(struct device *dev,`
`269`	`269`	`return false;`
`270`	`270`	`}`
`271`	`271`
	`272`	`+static inline unsigned long xen_get_swiotlb_free_pages(unsigned int order)`
	`273`	`+{`
	`274`	`+ return __get_free_pages(__GFP_NOWARN, order);`
	`275`	`+}`
	`276`	`+`
`272`	`277`	`#endif /* _ASM_X86_XEN_PAGE_H */`