[PATCH v2 1/3] xen/riscv: implement virt_to_maddr()

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Implement the virt_to_maddr() function to convert virtual addresses
to machine addresses, including checks for address ranges such as
the direct mapping area (DIRECTMAP_VIRT_START) and the Xen virtual
address space. To implement this, the phys_offset variable is made
accessible outside of riscv/mm.c.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in V2:
  - Drop casts in virt_to_maddr() for ASSERT which checks that VA is
    in the range of where Xen is located.
  - Add UL suffix for or XEN_VIRT_START by using _AC(..., UL) and add inclusion
    of <xen/const.h>
  - Add the comment above return which explains why there is no need
    to do " - XEN_VIRT_START.
---
 xen/arch/riscv/include/asm/config.h |  4 ++++
 xen/arch/riscv/include/asm/mm.h     | 17 ++++++++++++++++-
 xen/arch/riscv/mm.c                 |  2 +-
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/xen/arch/riscv/include/asm/config.h 
b/xen/arch/riscv/include/asm/config.h
index 7dbb235685..8884aeab16 100644
--- a/xen/arch/riscv/include/asm/config.h
+++ b/xen/arch/riscv/include/asm/config.h
@@ -155,6 +155,10 @@
 
 #define IDENT_AREA_SIZE 64
 
+#ifndef __ASSEMBLY__
+extern unsigned long phys_offset;
+#endif
+
 #endif /* __RISCV_CONFIG_H__ */
 /*
  * Local variables:
diff --git a/xen/arch/riscv/include/asm/mm.h b/xen/arch/riscv/include/asm/mm.h
index 4b7b00b850..0f7879d685 100644
--- a/xen/arch/riscv/include/asm/mm.h
+++ b/xen/arch/riscv/include/asm/mm.h
@@ -5,6 +5,7 @@
 
 #include <public/xen.h>
 #include <xen/bug.h>
+#include <xen/const.h>
 #include <xen/mm-frame.h>
 #include <xen/pdx.h>
 #include <xen/types.h>
@@ -28,7 +29,21 @@ static inline void *maddr_to_virt(paddr_t ma)
     return NULL;
 }
 
-#define virt_to_maddr(va) ({ BUG_ON("unimplemented"); 0; })
+static inline unsigned long virt_to_maddr(unsigned long va)
+{
+    ASSERT(va >= (DIRECTMAP_VIRT_START + DIRECTMAP_SIZE));
+    if ((va >= DIRECTMAP_VIRT_START) &&
+        (va < (DIRECTMAP_VIRT_START + DIRECTMAP_SIZE)))
+        return directmapoff_to_maddr(va - DIRECTMAP_VIRT_START);
+
+    BUILD_BUG_ON(XEN_VIRT_SIZE != MB(2));
+    ASSERT((va >> (PAGETABLE_ORDER + PAGE_SHIFT)) ==
+           (_AC(XEN_VIRT_START, UL) >> (PAGETABLE_ORDER + PAGE_SHIFT)));
+
+    /* phys_offset = load_start - XEN_VIRT_START */
+    return phys_offset + va;
+}
+#define virt_to_maddr(va) virt_to_maddr((unsigned long)(va))
 
 /* Convert between Xen-heap virtual addresses and machine frame numbers. */
 #define __virt_to_mfn(va)  mfn_x(maddr_to_mfn(virt_to_maddr(va)))
diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c
index 4a628aef83..7a1919e07e 100644
--- a/xen/arch/riscv/mm.c
+++ b/xen/arch/riscv/mm.c
@@ -26,7 +26,7 @@ struct mmu_desc {
     pte_t *pgtbl_base;
 };
 
-static unsigned long __ro_after_init phys_offset;
+unsigned long __ro_after_init phys_offset;
 
 #define LOAD_TO_LINK(addr) ((unsigned long)(addr) - phys_offset)
 #define LINK_TO_LOAD(addr) ((unsigned long)(addr) + phys_offset)
-- 
2.46.2