Re: [Xen-devel] [PATCH] Fix domheap structure allocation when NUMA=on

["Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx>]

Jan Beulich wrote:
> > > > "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx> 20.03.09 09:34 >>>
> > Jan Beulich wrote:
> > > > > > "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx> 20.03.09 06:05 >>>
> > > > DIRECTMAP_VIRT_END can't be passed to virt_to_mfn(), as it's just beyond 
> > > > direct map boundary and triggers ASSERT very early at boot time.
> > > While I agree to the analysis, I would think that this
> > >
> > > +              mfn + needed <= virt_to_mfn(DIRECTMAP_VIRT_END - PAGE_SIZE) )
> > >
> > > should rather be
> > >
> > > +              mfn + needed <= virt_to_mfn(DIRECTMAP_VIRT_END - 1) + 1 )
> > virt_to_mfn(DIRECTMAP_VIRT_END - 1) is equal to 
> Depending on whether DIRECTMAP_VIRT_END is the last byte or the first
> following byte. Using "- 1" avoids such a dependency.
>
> > virt_to_mfn(DIRECTMAP_VIRT_END - PAGE_SIZE). Why +1? We use '<=' here.
> Because on the left side of the comparison we also calculate the first
> following mfn, not the last included one.
Jan,
Thanks for the clarification!

Now I found another potential issue. Since mfn+needed could be equal to 
virt_to_mfn(DIRECTMAP_VIRT_END-1)+1, it can't be passed to mfn_to_virt() 
directly - the valid range is [0,DIRECT_MAP_BYTES>>PAGE_SHIFT).
Here is the patch to fix it. More assert and 32 bit counterpart are added.

Signed-off-by: Xiaowei Yang <xiaowei.yang@xxxxxxxxx>

Thanks,
xiaowei

diff -r 0477f9061c8a xen/common/page_alloc.c
--- a/xen/common/page_alloc.c   Fri Mar 20 17:42:46 2009 +0000
+++ b/xen/common/page_alloc.c   Mon Mar 23 03:04:18 2009 +0800
@@ -302,7 +302,8 @@ static unsigned long init_node_heap(int 
               (mfn + needed) <= (virt_to_mfn(DIRECTMAP_VIRT_END - 1) + 1) )
     {
         _heap[node] = mfn_to_virt(mfn);
-        avail[node] = mfn_to_virt(mfn + needed) - sizeof(**avail) * NR_ZONES;
+        avail[node] = mfn_to_virt(mfn + needed - 1) +
+                      PAGE_SIZE - sizeof(**avail) * NR_ZONES;
     }
 #endif
     else if ( get_order_from_bytes(sizeof(**_heap)) ==
diff -r 0477f9061c8a xen/include/asm-x86/x86_32/page.h
--- a/xen/include/asm-x86/x86_32/page.h Fri Mar 20 17:42:46 2009 +0000
+++ b/xen/include/asm-x86/x86_32/page.h Mon Mar 23 03:04:18 2009 +0800
@@ -27,9 +27,6 @@
 #define __PAGE_OFFSET           (0xFF000000)
 #define __XEN_VIRT_START        __PAGE_OFFSET
 
-#define virt_to_maddr(va) ((unsigned long)(va)-DIRECTMAP_VIRT_START)
-#define maddr_to_virt(ma) ((void *)((unsigned long)(ma)+DIRECTMAP_VIRT_START))
-
 #define VADDR_BITS              32
 #define VADDR_MASK              (~0UL)
 
@@ -43,6 +40,22 @@
 
 #include <xen/config.h>
 #include <asm/types.h>
+
+static inline unsigned long __virt_to_maddr(unsigned long va)
+{
+    ASSERT(va >= DIRECTMAP_VIRT_START && va < DIRECTMAP_VIRT_END);
+    return va - DIRECTMAP_VIRT_START;
+}
+#define virt_to_maddr(va)       \
+    (__virt_to_maddr((unsigned long)(va)))
+
+static inline void *__maddr_to_virt(unsigned long ma)
+{
+    ASSERT(ma < DIRECTMAP_VIRT_END - DIRECTMAP_VIRT_START);
+    return (void *)(ma + DIRECTMAP_VIRT_START);
+}
+#define maddr_to_virt(ma)       \
+    (__maddr_to_virt((unsigned long)(ma)))
 
 /* read access (should only be used for debug printk's) */
 typedef u64 intpte_t;
diff -r 0477f9061c8a xen/include/asm-x86/x86_64/page.h
--- a/xen/include/asm-x86/x86_64/page.h Fri Mar 20 17:42:46 2009 +0000
+++ b/xen/include/asm-x86/x86_64/page.h Mon Mar 23 03:04:42 2009 +0800
@@ -46,8 +46,14 @@ static inline unsigned long __virt_to_ma
 }
 #define virt_to_maddr(va)       \
     (__virt_to_maddr((unsigned long)(va)))
+
+static inline void *__maddr_to_virt(unsigned long ma)
+{
+    ASSERT(ma < DIRECTMAP_VIRT_END - DIRECTMAP_VIRT_START);
+    return (void *)(ma + DIRECTMAP_VIRT_START);
+}
 #define maddr_to_virt(ma)       \
-    ((void *)((unsigned long)(ma)+DIRECTMAP_VIRT_START))
+    (__maddr_to_virt((unsigned long)(ma)))
 
 /* read access (should only be used for debug printk's) */
 typedef u64 intpte_t;

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