[PATCH v2 for 4.20? 2/3] xen/riscv: update defintion of vmap_to_mfn()

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

vmap_to_mfn() uses virt_to_maddr(), which is designed to work with VA from
either the direct map region or Xen's linkage region (XEN_VIRT_START).
An assertion will occur if it is used with other regions, in particular for
the VMAP region.

Since RISC-V lacks a hardware feature to request the MMU to translate a VA to
a PA (as Arm does, for example), software page table walking (pt_walk()) is
used for the VMAP region to obtain the mfn from pte_t.

Fixes: 7db8d2bd9b ("xen/riscv: add minimal stuff to mm.h to build full Xen")
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in v2:
 - Update defintion of vmap_to_mfn() as pt_walk() now returns pte_t
   instead of paddr_t.
 - Update the commit message.
---
 xen/arch/riscv/include/asm/mm.h | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/xen/arch/riscv/include/asm/mm.h b/xen/arch/riscv/include/asm/mm.h
index 10a15a8b03..814a7035a8 100644
--- a/xen/arch/riscv/include/asm/mm.h
+++ b/xen/arch/riscv/include/asm/mm.h
@@ -23,8 +23,6 @@ extern vaddr_t directmap_virt_start;
 #define gaddr_to_gfn(ga)    _gfn(paddr_to_pfn(ga))
 #define mfn_to_maddr(mfn)   pfn_to_paddr(mfn_x(mfn))
 #define maddr_to_mfn(ma)    _mfn(paddr_to_pfn(ma))
-#define vmap_to_mfn(va)     maddr_to_mfn(virt_to_maddr((vaddr_t)(va)))
-#define vmap_to_page(va)    mfn_to_page(vmap_to_mfn(va))
 
 static inline void *maddr_to_virt(paddr_t ma)
 {
@@ -160,6 +158,18 @@ static inline struct page_info *virt_to_page(const void *v)
 
 pte_t * pt_walk(vaddr_t va, unsigned int *pte_level);
 
+static inline mfn_t vmap_to_mfn_(vaddr_t va)
+{
+    pte_t *entry = pt_walk(va, NULL);
+
+    BUG_ON(!pte_is_mapping(*entry));
+
+    return mfn_from_pte(*entry);
+}
+
+#define vmap_to_mfn(va)     vmap_to_mfn_((vaddr_t)va)
+#define vmap_to_page(va)    mfn_to_page(vmap_to_mfn(va))
+
 /*
  * Common code requires get_page_type and put_page_type.
  * We don't care about typecounts so we just do the minimum to make it
-- 
2.48.1