[PATCH v1 2/5] xen/riscv: implement maddr_to_virt()

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Implement the `maddr_to_virt()` function to convert a machine address
to a virtual address. This function is specifically designed to be used
only for the DIRECTMAP region, so a check has been added to ensure that
the address does not exceed `DIRECTMAP_SIZE`.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
 xen/arch/riscv/include/asm/mm.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/xen/arch/riscv/include/asm/mm.h b/xen/arch/riscv/include/asm/mm.h
index ebb142502e..0396e66f47 100644
--- a/xen/arch/riscv/include/asm/mm.h
+++ b/xen/arch/riscv/include/asm/mm.h
@@ -25,8 +25,12 @@
 
 static inline void *maddr_to_virt(paddr_t ma)
 {
-    BUG_ON("unimplemented");
-    return NULL;
+    /* Offset in the direct map, accounting for pdx compression */
+    unsigned long va_offset = maddr_to_directmapoff(ma);
+
+    ASSERT(va_offset < DIRECTMAP_SIZE);
+
+    return (void *)(DIRECTMAP_VIRT_START + va_offset);
 }
 
 /*
-- 
2.47.0