[PATCH RFC 1/2] xen/page_alloc: Add size_align parameter to provide MFNs which are size aligned.

[Konrad Rzeszutek Wilk <konrad@kernel.org>]

This is to support the requirement that exists in PV dom0
when doing DMA requests:

"dma_alloc_coherent()
[...]
The CPU virtual address and the DMA address are both guaranteed to be
aligned to the smallest PAGE_SIZE order which is greater than or equal
to the requested size.  This invariant exists (for example) to guarantee
that if you allocate a chunk which is smaller than or equal to 64
kilobytes, the extent of the buffer you receive will not cross a 64K
boundary."

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 xen/common/memory.c         |  3 +++
 xen/common/page_alloc.c     | 22 +++++++++++++++++++++-
 xen/include/public/memory.h |  2 ++
 xen/include/xen/mm.h        |  2 ++
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/xen/common/memory.c b/xen/common/memory.c
index 21797ca..a4c0c54 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -475,6 +475,9 @@ static long memory_exchange(XEN_GUEST_HANDLE_PARAM(xen_memory_exchange_t) arg)
         (BITS_PER_LONG+PAGE_SHIFT)));
     memflags |= MEMF_node(XENMEMF_get_node(exch.out.mem_flags));
 
+    if ( XENMEMF_align_size & exch.out.mem_flags && is_hardware_domain(d) )
+        memflags |= MEMF_size_align;
+
     for ( i = (exch.nr_exchanged >> in_chunk_order);
           i < (exch.in.nr_extents >> in_chunk_order);
           i++ )
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index ae2476d..e43f52f 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -738,7 +738,7 @@ static struct page_info *alloc_heap_pages(
      * Others try tmem pools then fail.  This is a workaround until all
      * post-dom0-creation-multi-page allocations can be eliminated.
      */
-    if ( ((order == 0) || (order >= 9)) &&
+    if ( ((order == 0) || (order >= 9)) && !(memflags & MEMF_size_align) &&
          (total_avail_pages <= midsize_alloc_zone_pages) &&
          tmem_freeable_pages() )
         goto try_tmem;
@@ -752,14 +752,34 @@ static struct page_info *alloc_heap_pages(
     {
         zone = zone_hi;
         do {
+            struct page_info *old = NULL;
+
             /* Check if target node can support the allocation. */
             if ( !avail[node] || (avail[node][zone] < request) )
                 continue;
 
             /* Find smallest order which can satisfy the request. */
             for ( j = order; j <= MAX_ORDER; j++ )
+            {
+ next_page:
                 if ( (pg = page_list_remove_head(&heap(node, zone, j))) )
+                {
+                    if ( memflags & MEMF_size_align )
+                    {
+                        if (pg == old)
+                            continue;
+
+                        if ( (page_to_mfn(pg) % request ) == 0 )
+                            goto found;
+
+                        page_list_add_tail(pg, &heap(node, zone, j));
+                        old = pg;
+                        pg = NULL;
+                        goto next_page;
+                    }
                     goto found;
+                }
+            }
         } while ( zone-- > zone_lo ); /* careful: unsigned zone may wrap */
 
         if ( (memflags & MEMF_exact_node) && req_node != NUMA_NO_NODE )
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index 5bf840f..311e7d8 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -58,6 +58,8 @@
 #define XENMEMF_exact_node(n) (XENMEMF_node(n) | XENMEMF_exact_node_request)
 /* Flag to indicate the node specified is virtual node */
 #define XENMEMF_vnode  (1<<18)
+/* Flag to indicate the allocation to be size aligned. */
+#define XENMEMF_align_size (1U<<19)
 #endif
 
 struct xen_memory_reservation {
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index 76fbb82..c505170 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -224,6 +224,8 @@ struct npfec {
 #define  MEMF_no_owner    (1U<<_MEMF_no_owner)
 #define _MEMF_no_tlbflush 6
 #define  MEMF_no_tlbflush (1U<<_MEMF_no_tlbflush)
+#define _MEMF_size_align  7
+#define  MEMF_size_align  (1U<<_MEMF_size_align)
 #define _MEMF_node        8
 #define  MEMF_node_mask   ((1U << (8 * sizeof(nodeid_t))) - 1)
 #define  MEMF_node(n)     ((((n) + 1) & MEMF_node_mask) << _MEMF_node)
-- 
2.7.4


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel