[PATCH v2 2/5] mm: Factor out the pdx compression logic in ma/va converters

[Alejandro Vallejo <alejandro.vallejo@cloud.com>]

This patch factors out the pdx compression logic hardcoded in both ports
for the maddr<->vaddr conversion functions.

Touches both x86 and arm ports.

Signed-off-by: Alejandro Vallejo <alejandro.vallejo@cloud.com>
---
v2:
  * Cast variable to u64 before shifting left to avoid overflow (Julien)
---
 xen/arch/arm/include/asm/mm.h          |  3 +--
 xen/arch/x86/include/asm/x86_64/page.h | 28 +++++++++++---------------
 xen/include/xen/pdx.h                  | 25 +++++++++++++++++++++++
 3 files changed, 38 insertions(+), 18 deletions(-)

diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h
index 5b530f0f40..c0d7f0f181 100644
--- a/xen/arch/arm/include/asm/mm.h
+++ b/xen/arch/arm/include/asm/mm.h
@@ -319,8 +319,7 @@ static inline void *maddr_to_virt(paddr_t ma)
            (DIRECTMAP_SIZE >> PAGE_SHIFT));
     return (void *)(XENHEAP_VIRT_START -
                     (directmap_base_pdx << PAGE_SHIFT) +
-                    ((ma & ma_va_bottom_mask) |
-                     ((ma & ma_top_mask) >> pfn_pdx_hole_shift)));
+                    maddr_to_directmapoff(ma));
 }
 #endif
 
diff --git a/xen/arch/x86/include/asm/x86_64/page.h b/xen/arch/x86/include/asm/x86_64/page.h
index 53faa7875b..b589c93e77 100644
--- a/xen/arch/x86/include/asm/x86_64/page.h
+++ b/xen/arch/x86/include/asm/x86_64/page.h
@@ -36,26 +36,22 @@ static inline unsigned long __virt_to_maddr(unsigned long va)
 {
     ASSERT(va < DIRECTMAP_VIRT_END);
     if ( va >= DIRECTMAP_VIRT_START )
-        va -= DIRECTMAP_VIRT_START;
-    else
-    {
-        BUILD_BUG_ON(XEN_VIRT_END - XEN_VIRT_START != GB(1));
-        /* Signed, so ((long)XEN_VIRT_START >> 30) fits in an imm32. */
-        ASSERT(((long)va >> (PAGE_ORDER_1G + PAGE_SHIFT)) ==
-               ((long)XEN_VIRT_START >> (PAGE_ORDER_1G + PAGE_SHIFT)));
-
-        va += xen_phys_start - XEN_VIRT_START;
-    }
-    return (va & ma_va_bottom_mask) |
-           ((va << pfn_pdx_hole_shift) & ma_top_mask);
+        return directmapoff_to_maddr(va - DIRECTMAP_VIRT_START);
+
+    BUILD_BUG_ON(XEN_VIRT_END - XEN_VIRT_START != GB(1));
+    /* Signed, so ((long)XEN_VIRT_START >> 30) fits in an imm32. */
+    ASSERT(((long)va >> (PAGE_ORDER_1G + PAGE_SHIFT)) ==
+           ((long)XEN_VIRT_START >> (PAGE_ORDER_1G + PAGE_SHIFT)));
+
+    return xen_phys_start + va - XEN_VIRT_START;
 }
 
 static inline void *__maddr_to_virt(unsigned long ma)
 {
-    ASSERT(pfn_to_pdx(ma >> PAGE_SHIFT) < (DIRECTMAP_SIZE >> PAGE_SHIFT));
-    return (void *)(DIRECTMAP_VIRT_START +
-                    ((ma & ma_va_bottom_mask) |
-                     ((ma & ma_top_mask) >> pfn_pdx_hole_shift)));
+    /* Offset in the direct map, accounting for pdx compression */
+    size_t va_offset = maddr_to_directmapoff(ma);
+    ASSERT(va_offset < DIRECTMAP_SIZE);
+    return (void *)(DIRECTMAP_VIRT_START + va_offset);
 }
 
 /* read access (should only be used for debug printk's) */
diff --git a/xen/include/xen/pdx.h b/xen/include/xen/pdx.h
index de5439a5e5..d96f03d6e6 100644
--- a/xen/include/xen/pdx.h
+++ b/xen/include/xen/pdx.h
@@ -160,6 +160,31 @@ static inline unsigned long pdx_to_pfn(unsigned long pdx)
 #define mfn_to_pdx(mfn) pfn_to_pdx(mfn_x(mfn))
 #define pdx_to_mfn(pdx) _mfn(pdx_to_pfn(pdx))
 
+/**
+ * Computes the offset into the direct map of an maddr
+ *
+ * @param ma Machine address
+ * @return Offset on the direct map where that
+ *         machine address can be accessed
+ */
+static inline unsigned long maddr_to_directmapoff(uint64_t ma)
+{
+    return ((ma & ma_top_mask) >> pfn_pdx_hole_shift) |
+           (ma & ma_va_bottom_mask);
+}
+
+/**
+ * Computes a machine address given a direct map offset
+ *
+ * @param offset Offset into the direct map
+ * @return Corresponding machine address of that virtual location
+ */
+static inline uint64_t directmapoff_to_maddr(unsigned long offset)
+{
+    return (((uint64_t)offset << pfn_pdx_hole_shift) & ma_top_mask) |
+           (offset & ma_va_bottom_mask);
+}
+
 /**
  * Initializes global variables with information about the compressible
  * range of the current memory regions.
-- 
2.34.1