[Xen-changelog] [xen stable-4.7] page-alloc/x86: don't restrict DMA heap to node 0

[patchbot@xxxxxxx]

commit 5b5abe1e848f2ea735b3ba930a0208c4e9e1e752
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Aug 26 10:19:38 2016 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Aug 26 10:19:38 2016 +0200

    page-alloc/x86: don't restrict DMA heap to node 0
    
    When node zero has no memory, the DMA bit width will end up getting set
    to 9, which is obviously not helpful to hold back a reasonable amount
    of low enough memory for Dom0 to use for DMA purposes. Find the lowest
    node with memory below 4Gb instead.
    
    Introduce arch_get_dma_bitsize() to keep this arch-specific logic out
    of common code.
    
    Also adjust the original calculation: I think the subtraction of 1
    should have been part of the flsl() argument rather than getting
    applied to its result. And while previously the division by 4 was valid
    to be done on the flsl() result, this now also needs to be converted,
    as is should only be applied to the spanned pages value.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Julien Grall <julien.grall@xxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: d0d6597d3d682f324b6a79e3278e6f5bb6bad153
    master date: 2016-08-11 13:35:50 +0200
---
 xen/arch/x86/numa.c        | 24 +++++++++++++++++++-----
 xen/common/page_alloc.c    | 11 +----------
 xen/include/asm-arm/numa.h |  5 +++++
 xen/include/asm-x86/numa.h |  1 +
 4 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/numa.c b/xen/arch/x86/numa.c
index e243e06..b66d123 100644
--- a/xen/arch/x86/numa.c
+++ b/xen/arch/x86/numa.c
@@ -355,11 +355,25 @@ void __init init_cpu_to_node(void)
     }
 }
 
-EXPORT_SYMBOL(cpu_to_node);
-EXPORT_SYMBOL(node_to_cpumask);
-EXPORT_SYMBOL(memnode_shift);
-EXPORT_SYMBOL(memnodemap);
-EXPORT_SYMBOL(node_data);
+unsigned int __init arch_get_dma_bitsize(void)
+{
+    unsigned int node;
+
+    for_each_online_node(node)
+        if ( node_spanned_pages(node) &&
+             !(node_start_pfn(node) >> (32 - PAGE_SHIFT)) )
+            break;
+    if ( node >= MAX_NUMNODES )
+        panic("No node with memory below 4Gb");
+
+    /*
+     * Try to not reserve the whole node's memory for DMA, but dividing
+     * its spanned pages by (arbitrarily chosen) 4.
+     */
+    return min_t(unsigned int,
+                 flsl(node_start_pfn(node) + node_spanned_pages(node) / 4 - 1)
+                 + PAGE_SHIFT, 32);
+}
 
 static void dump_numa(unsigned char key)
 {
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 98e30e5..fabfe0a 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -1368,16 +1368,7 @@ void __init end_boot_allocator(void)
     init_heap_pages(virt_to_page(bootmem_region_list), 1);
 
     if ( !dma_bitsize && (num_online_nodes() > 1) )
-    {
-#ifdef CONFIG_X86
-        dma_bitsize = min_t(unsigned int,
-                            flsl(NODE_DATA(0)->node_spanned_pages) - 1
-                            + PAGE_SHIFT - 2,
-                            32);
-#else
-        dma_bitsize = 32;
-#endif
-    }
+        dma_bitsize = arch_get_dma_bitsize();
 
     printk("Domain heap initialised");
     if ( dma_bitsize )
diff --git a/xen/include/asm-arm/numa.h b/xen/include/asm-arm/numa.h
index a00cb7c..a2c1a34 100644
--- a/xen/include/asm-arm/numa.h
+++ b/xen/include/asm-arm/numa.h
@@ -17,6 +17,11 @@ static inline __attribute__((pure)) nodeid_t 
phys_to_nid(paddr_t addr)
 #define node_start_pfn(nid) (pdx_to_pfn(frametable_base_pdx))
 #define __node_distance(a, b) (20)
 
+static inline unsigned int arch_get_dma_bitsize(void)
+{
+    return 32;
+}
+
 #endif /* __ARCH_ARM_NUMA_H */
 /*
  * Local variables:
diff --git a/xen/include/asm-x86/numa.h b/xen/include/asm-x86/numa.h
index 9a2d7cc..1c5ad37 100644
--- a/xen/include/asm-x86/numa.h
+++ b/xen/include/asm-x86/numa.h
@@ -86,5 +86,6 @@ extern int valid_numa_range(u64 start, u64 end, nodeid_t 
node);
 
 void srat_parse_regions(u64 addr);
 extern u8 __node_distance(nodeid_t a, nodeid_t b);
+unsigned int arch_get_dma_bitsize(void);
 
 #endif
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.7

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
https://lists.xenproject.org/xen-changelog