[PATCH v2 10/17] xen/riscv: implement guest_physmap_add_entry() for mapping GFNs to MFNs

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Introduce an initial implementation of guest_physmap_add_entry() on RISC-V
by adding a basic framework to insert guest physical memory mappings.
This allows mapping a range of GFNs to MFNs using a placeholder
p2m_set_entry() function, which currently returns -EOPNOTSUPP.

Changes included:
- Promoting guest_physmap_add_entry() from a stub to a functional
  interface calling a new p2m_insert_mapping() helper.
- Adding map_regions_p2mt() for generic mapping purposes.
- Introducing p2m_insert_mapping() and a skeleton for p2m_set_entry() to
  prepare for future support of actual page table manipulation.
- Enclosing the actual mapping logic within
  p2m_write_lock() / p2m_write_unlock() to ensure safe concurrent
  updates to the P2M.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in v2:
 - This changes were part of "xen/riscv: implement p2m mapping functionality".
   No additional signigicant changes were done.
---
 xen/arch/riscv/include/asm/p2m.h | 12 ++++------
 xen/arch/riscv/p2m.c             | 41 ++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/xen/arch/riscv/include/asm/p2m.h b/xen/arch/riscv/include/asm/p2m.h
index 0c05b58992..af2025b9fd 100644
--- a/xen/arch/riscv/include/asm/p2m.h
+++ b/xen/arch/riscv/include/asm/p2m.h
@@ -118,14 +118,10 @@ static inline int 
guest_physmap_mark_populate_on_demand(struct domain *d,
     return -EOPNOTSUPP;
 }
 
-static inline int guest_physmap_add_entry(struct domain *d,
-                                          gfn_t gfn, mfn_t mfn,
-                                          unsigned long page_order,
-                                          p2m_type_t t)
-{
-    BUG_ON("unimplemented");
-    return -EINVAL;
-}
+int guest_physmap_add_entry(struct domain *d,
+                            gfn_t gfn, mfn_t mfn,
+                            unsigned long page_order,
+                            p2m_type_t t);
 
 /* Untyped version for RAM only, for compatibility */
 static inline int __must_check
diff --git a/xen/arch/riscv/p2m.c b/xen/arch/riscv/p2m.c
index 2419a61d8c..cea37c8bda 100644
--- a/xen/arch/riscv/p2m.c
+++ b/xen/arch/riscv/p2m.c
@@ -324,3 +324,44 @@ int p2m_set_allocation(struct domain *d, unsigned long 
pages, bool *preempted)
 
     return 0;
 }
+
+static int p2m_set_entry(struct p2m_domain *p2m,
+                         gfn_t sgfn,
+                         unsigned long nr,
+                         mfn_t smfn,
+                         p2m_type_t t,
+                         p2m_access_t a)
+{
+    return -EOPNOTSUPP;
+}
+
+static int p2m_insert_mapping(struct domain *d, gfn_t start_gfn,
+                              unsigned long nr, mfn_t mfn, p2m_type_t t)
+{
+    struct p2m_domain *p2m = p2m_get_hostp2m(d);
+    int rc;
+
+    p2m_write_lock(p2m);
+    rc = p2m_set_entry(p2m, start_gfn, nr, mfn, t, p2m->default_access);
+    p2m_write_unlock(p2m);
+
+    return rc;
+}
+
+int map_regions_p2mt(struct domain *d,
+                     gfn_t gfn,
+                     unsigned long nr,
+                     mfn_t mfn,
+                     p2m_type_t p2mt)
+{
+    return p2m_insert_mapping(d, gfn, nr, mfn, p2mt);
+}
+
+int guest_physmap_add_entry(struct domain *d,
+                            gfn_t gfn,
+                            mfn_t mfn,
+                            unsigned long page_order,
+                            p2m_type_t t)
+{
+    return p2m_insert_mapping(d, gfn, (1 << page_order), mfn, t);
+}
-- 
2.49.0