[xen master] xen/riscv: implement function to map memory in guest p2m

[patchbot@xxxxxxx]

commit 96553849a32e5240e444db09b92c559480faffa0
Author:     Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
AuthorDate: Tue Dec 16 17:55:19 2025 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Dec 18 14:24:17 2025 +0100

    xen/riscv: implement function to map memory in guest p2m
    
    Implement map_regions_p2mt() to map a region in the guest p2m with
    a specific p2m type. The memory attributes will be derived from the
    p2m type. This function is used in dom0less common
    code.
    
    To implement it, introduce:
    - p2m_write_(un)lock() to ensure safe concurrent updates to the P2M.
      As part of this change, introduce p2m_tlb_flush_sync() and
      p2m_force_tlb_flush_sync().
    - A stub for p2m_set_range() to map a range of GFNs to MFNs.
    - p2m_insert_mapping().
    - p2m_is_write_locked().
    
    Drop guest_physmap_add_entry() and call map_regions_p2mt() directly
    from guest_physmap_add_page(), making guest_physmap_add_entry()
    unnecessary.
    
    Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/riscv/include/asm/p2m.h | 31 +++++++++++++++------
 xen/arch/riscv/p2m.c             | 60 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 82 insertions(+), 9 deletions(-)

diff --git a/xen/arch/riscv/include/asm/p2m.h b/xen/arch/riscv/include/asm/p2m.h
index 1c89838408..9acd6a64a8 100644
--- a/xen/arch/riscv/include/asm/p2m.h
+++ b/xen/arch/riscv/include/asm/p2m.h
@@ -128,21 +128,22 @@ 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;
-}
+/*
+ * Map a region in the guest's hostp2m p2m with a specific p2m type.
+ * The memory attributes will be derived from the p2m type.
+ */
+int map_regions_p2mt(struct domain *d,
+                     gfn_t gfn,
+                     unsigned long nr,
+                     mfn_t mfn,
+                     p2m_type_t p2mt);
 
 /* Untyped version for RAM only, for compatibility */
 static inline int __must_check
 guest_physmap_add_page(struct domain *d, gfn_t gfn, mfn_t mfn,
                        unsigned int page_order)
 {
-    return guest_physmap_add_entry(d, gfn, mfn, page_order, p2m_ram_rw);
+    return map_regions_p2mt(d, gfn, BIT(page_order, UL), mfn, p2m_ram_rw);
 }
 
 static inline mfn_t gfn_to_mfn(struct domain *d, gfn_t gfn)
@@ -166,6 +167,18 @@ unsigned char get_max_supported_mode(void);
 
 int p2m_init(struct domain *d);
 
+static inline void p2m_write_lock(struct p2m_domain *p2m)
+{
+    write_lock(&p2m->lock);
+}
+
+void p2m_write_unlock(struct p2m_domain *p2m);
+
+static inline bool p2m_is_write_locked(struct p2m_domain *p2m)
+{
+    return rw_is_write_locked(&p2m->lock);
+}
+
 unsigned long construct_hgatp(const struct p2m_domain *p2m, uint16_t vmid);
 
 #endif /* ASM__RISCV__P2M_H */
diff --git a/xen/arch/riscv/p2m.c b/xen/arch/riscv/p2m.c
index d14757331f..8bb197f9b3 100644
--- a/xen/arch/riscv/p2m.c
+++ b/xen/arch/riscv/p2m.c
@@ -110,6 +110,41 @@ void __init guest_mm_init(void)
     local_hfence_gvma_all();
 }
 
+/*
+ * Force a synchronous P2M TLB flush.
+ *
+ * Must be called with the p2m lock held.
+ */
+static void p2m_tlb_flush(struct p2m_domain *p2m)
+{
+    const struct domain *d = p2m->domain;
+
+    ASSERT(p2m_is_write_locked(p2m));
+
+    p2m->need_flush = false;
+
+    sbi_remote_hfence_gvma(d->dirty_cpumask, 0, 0);
+}
+
+void p2m_tlb_flush_sync(struct p2m_domain *p2m)
+{
+    if ( p2m->need_flush )
+        p2m_tlb_flush(p2m);
+}
+
+/* Unlock the P2M and do a P2M TLB flush if necessary */
+void p2m_write_unlock(struct p2m_domain *p2m)
+{
+    /*
+     * The final flush is done with the P2M write lock taken to avoid
+     * someone else modifying the P2M before the TLB invalidation has
+     * completed.
+     */
+    p2m_tlb_flush_sync(p2m);
+
+    write_unlock(&p2m->lock);
+}
+
 static void clear_and_clean_page(struct page_info *page, bool clean_dcache)
 {
     void *p = __map_domain_page(page);
@@ -238,3 +273,28 @@ int p2m_set_allocation(struct domain *d, unsigned long 
pages, bool *preempted)
 
     return rc;
 }
+
+static int p2m_set_range(struct p2m_domain *p2m,
+                         gfn_t sgfn,
+                         unsigned long nr,
+                         mfn_t smfn,
+                         p2m_type_t t)
+{
+    return -EOPNOTSUPP;
+}
+
+int map_regions_p2mt(struct domain *d,
+                     gfn_t gfn,
+                     unsigned long nr,
+                     mfn_t mfn,
+                     p2m_type_t p2mt)
+{
+    struct p2m_domain *p2m = p2m_get_hostp2m(d);
+    int rc;
+
+    p2m_write_lock(p2m);
+    rc = p2m_set_range(p2m, gfn, nr, mfn, p2mt);
+    p2m_write_unlock(p2m);
+
+    return rc;
+}
--
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