[PATCH] x86/mem: Make mem_hotadd_check() more legible

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Introduce a ROUND() macro to mirror ROUNDUP().  Use both to remove all the
opencoded rounding in mem_hotadd_check().  Fix other minor style issues.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>

The compiled binary is identical.
---
 xen/arch/x86/x86_64/mm.c | 31 +++++++++++++------------------
 xen/include/xen/macros.h |  1 +
 2 files changed, 14 insertions(+), 18 deletions(-)

diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 60db439af3ec..38f978cab269 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -1159,10 +1159,10 @@ static int mem_hotadd_check(unsigned long spfn, 
unsigned long epfn)
 {
     unsigned long s, e, length, sidx, eidx;
 
-    if ( (spfn >= epfn) )
+    if ( spfn >= epfn )
         return 0;
 
-    if (pfn_to_pdx(epfn) > FRAMETABLE_NR)
+    if ( pfn_to_pdx(epfn) > FRAMETABLE_NR )
         return 0;
 
     if ( (spfn | epfn) & ((1UL << PAGETABLE_ORDER) - 1) )
@@ -1172,10 +1172,9 @@ static int mem_hotadd_check(unsigned long spfn, unsigned 
long epfn)
         return 0;
 
     /* Make sure the new range is not present now */
-    sidx = ((pfn_to_pdx(spfn) + PDX_GROUP_COUNT - 1)  & ~(PDX_GROUP_COUNT - 1))
-            / PDX_GROUP_COUNT;
-    eidx = (pfn_to_pdx(epfn - 1) & ~(PDX_GROUP_COUNT - 1)) / PDX_GROUP_COUNT;
-    if (sidx >= eidx)
+    sidx = ROUNDUP(pfn_to_pdx(spfn),     PDX_GROUP_COUNT) / PDX_GROUP_COUNT;
+    eidx = ROUND  (pfn_to_pdx(epfn - 1), PDX_GROUP_COUNT) / PDX_GROUP_COUNT;
+    if ( sidx >= eidx )
         return 0;
 
     s = find_next_zero_bit(pdx_group_valid, eidx, sidx);
@@ -1186,28 +1185,24 @@ static int mem_hotadd_check(unsigned long spfn, 
unsigned long epfn)
         return 0;
 
     /* Caculate at most required m2p/compat m2p/frametable pages */
-    s = (spfn & ~((1UL << (L2_PAGETABLE_SHIFT - 3)) - 1));
-    e = (epfn + (1UL << (L2_PAGETABLE_SHIFT - 3)) - 1) &
-            ~((1UL << (L2_PAGETABLE_SHIFT - 3)) - 1);
+    s = ROUND  (spfn, 1UL << (L2_PAGETABLE_SHIFT - 3));
+    e = ROUNDUP(epfn, 1UL << (L2_PAGETABLE_SHIFT - 3));
 
     length = (e - s) * sizeof(unsigned long);
 
-    s = (spfn & ~((1UL << (L2_PAGETABLE_SHIFT - 2)) - 1));
-    e = (epfn + (1UL << (L2_PAGETABLE_SHIFT - 2)) - 1) &
-            ~((1UL << (L2_PAGETABLE_SHIFT - 2)) - 1);
-
-    e = min_t(unsigned long, e,
+    s =     ROUND  (spfn, 1ULL << (L2_PAGETABLE_SHIFT - 2));
+    e = min(ROUNDUP(epfn, 1ULL << (L2_PAGETABLE_SHIFT - 2)),
             (RDWR_COMPAT_MPT_VIRT_END - RDWR_COMPAT_MPT_VIRT_START) >> 2);
 
     if ( e > s )
-        length += (e -s) * sizeof(unsigned int);
+        length += (e - s) * sizeof(unsigned int);
 
-    s = pfn_to_pdx(spfn) & ~(PDX_GROUP_COUNT - 1);
-    e = ( pfn_to_pdx(epfn) + (PDX_GROUP_COUNT - 1) ) & ~(PDX_GROUP_COUNT - 1);
+    s = ROUND  (pfn_to_pdx(spfn), PDX_GROUP_COUNT);
+    e = ROUNDUP(pfn_to_pdx(epfn), PDX_GROUP_COUNT);
 
     length += (e - s) * sizeof(struct page_info);
 
-    if ((length >> PAGE_SHIFT) > (epfn - spfn))
+    if ( (length >> PAGE_SHIFT) > (epfn - spfn) )
         return 0;
 
     return 1;
diff --git a/xen/include/xen/macros.h b/xen/include/xen/macros.h
index 7b92d345044d..ceeffcaa95ff 100644
--- a/xen/include/xen/macros.h
+++ b/xen/include/xen/macros.h
@@ -1,6 +1,7 @@
 #ifndef __MACROS_H__
 #define __MACROS_H__
 
+#define ROUND(x, a)   ((x) & ~((a) - 1))
 #define ROUNDUP(x, a) (((x) + (a) - 1) & ~((a) - 1))
 
 #define IS_ALIGNED(val, align) (!((val) & ((align) - 1)))

base-commit: b1c16800e52743d9afd9af62c810f03af16dd942
-- 
2.30.2