[Xen-devel] [PATCH v2] boot allocator: Use arch helper for virt_to_mfn on DIRECTMAP

[vijay.kilari@xxxxxxxxx]

From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxx>

On ARM, virt_to_mfn uses the hardware for address
translation. So if the virtual address is not mapped translation
fault is raised.On ARM, DIRECTMAP_VIRT region is direct mapped.

On ARM with NUMA, While initializing second memory node,
panic is triggered from init_node_heap() when virt_to_mfn()
is called for DIRECTMAP_VIRT region address.
Here the check is made to ensure that MFN less than max MFN mapped.
The max MFN is found by calling virt_to_mfn of DIRECTMAP_VIRT_END
region. Since DIRECMAP_VIRT region is not mapped to any virtual address
on ARM, it fails.

In this patch, instead of calling virt_to_mfn(), arch helper
arch_mfn_below_directmap_max_mfn() is introduced. On ARM this arch helper
will return 1 always and for x86 this helper does virt_to_mfn.

Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxx>
---
 xen/common/page_alloc.c    |  7 ++-----
 xen/include/asm-arm/mm.h   |  7 +++++++
 xen/include/asm-x86/page.h | 16 ++++++++++++++++
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 42c20cb..85322cd 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -520,9 +520,6 @@ static unsigned long init_node_heap(int node, unsigned long 
mfn,
     unsigned long needed = (sizeof(**_heap) +
                             sizeof(**avail) * NR_ZONES +
                             PAGE_SIZE - 1) >> PAGE_SHIFT;
-#ifdef DIRECTMAP_VIRT_END
-    unsigned long eva = min(DIRECTMAP_VIRT_END, HYPERVISOR_VIRT_END);
-#endif
     int i, j;
 
     if ( !first_node_initialised )
@@ -534,7 +531,7 @@ static unsigned long init_node_heap(int node, unsigned long 
mfn,
     }
 #ifdef DIRECTMAP_VIRT_END
     else if ( *use_tail && nr >= needed &&
-              (mfn + nr) <= (virt_to_mfn(eva - 1) + 1) &&
+              arch_mfn_below_directmap_max_mfn(mfn + nr) &&
               (!xenheap_bits ||
                !((mfn + nr - 1) >> (xenheap_bits - PAGE_SHIFT))) )
     {
@@ -543,7 +540,7 @@ static unsigned long init_node_heap(int node, unsigned long 
mfn,
                       PAGE_SIZE - sizeof(**avail) * NR_ZONES;
     }
     else if ( nr >= needed &&
-              (mfn + needed) <= (virt_to_mfn(eva - 1) + 1) &&
+              arch_mfn_below_directmap_max_mfn(mfn + needed) &&
               (!xenheap_bits ||
                !((mfn + needed - 1) >> (xenheap_bits - PAGE_SHIFT))) )
     {
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index 60ccbf3..f0c90c2 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -260,6 +260,13 @@ static inline int gvirt_to_maddr(vaddr_t va, paddr_t *pa, 
unsigned int flags)
 #define virt_to_mfn(va)   (virt_to_maddr(va) >> PAGE_SHIFT)
 #define mfn_to_virt(mfn)  (maddr_to_virt((paddr_t)(mfn) << PAGE_SHIFT))
 
+/*
+ * On ARM DIRECTMAP_VIRT region is directly mapped. Hence return true;
+ */
+static inline bool_t arch_mfn_below_directmap_max_mfn(unsigned long mfn)
+{
+    return 1;
+}
 
 /* Convert between Xen-heap virtual addresses and page-info structures. */
 static inline struct page_info *virt_to_page(const void *v)
diff --git a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h
index 46faffc..3ea5310 100644
--- a/xen/include/asm-x86/page.h
+++ b/xen/include/asm-x86/page.h
@@ -18,6 +18,7 @@
 #ifndef __ASSEMBLY__
 # include <asm/types.h>
 # include <xen/lib.h>
+# include <xen/kernel.h>
 #endif
 
 #include <asm/x86_64/page.h>
@@ -374,6 +375,21 @@ perms_strictly_increased(uint32_t old_flags, uint32_t 
new_flags)
     return ((of | (of ^ nf)) == nf);
 }
 
+/*
+ * x86 maps DIRECTMAP_VIRT to physical memory. Get the mfn for directmap
+ * memory region.
+ */
+static inline bool_t arch_mfn_below_directmap_max_mfn(unsigned long mfn)
+{
+#ifdef DIRECTMAP_VIRT_END
+    unsigned long eva = min(DIRECTMAP_VIRT_END, HYPERVISOR_VIRT_END);
+
+    return mfn <= (virt_to_mfn(eva - 1) + 1);
+#else
+    return 0;
+#endif
+}
+
 #endif /* !__ASSEMBLY__ */
 
 #define PAGE_ALIGN(x) (((x) + PAGE_SIZE - 1) & PAGE_MASK)
-- 
2.7.4


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