[PATCH 2/8] xen/arm: Implement p2m_get_entry for MPU systems

[Luca Fancellu <luca.fancellu@xxxxxxx>]

From: Penny Zheng <Penny.Zheng@xxxxxxx>

Implement the function p2m_get_entry for MPU systems, which is
responsible for looking up an entry in the p2m table.

Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
Signed-off-by: Hari Limaye <hari.limaye@xxxxxxx>
---
 xen/arch/arm/include/asm/mpu/p2m.h |  5 ++
 xen/arch/arm/mpu/p2m.c             | 76 ++++++++++++++++++++++++++++--
 2 files changed, 77 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/include/asm/mpu/p2m.h 
b/xen/arch/arm/include/asm/mpu/p2m.h
index b9c7be2d9dcc..d0ec8a77a15a 100644
--- a/xen/arch/arm/include/asm/mpu/p2m.h
+++ b/xen/arch/arm/include/asm/mpu/p2m.h
@@ -31,6 +31,11 @@ static inline p2m_type_t region_get_p2m(pr_t *pr)
     return pr->p2m_type;
 }
 
+static inline bool region_is_p2m_valid(pr_t *pr)
+{
+    return (pr->p2m_type != p2m_invalid);
+}
+
 #endif /* __ARM_MPU_P2M_H__ */
 
 /*
diff --git a/xen/arch/arm/mpu/p2m.c b/xen/arch/arm/mpu/p2m.c
index 4a8595b1b25e..681717eacf37 100644
--- a/xen/arch/arm/mpu/p2m.c
+++ b/xen/arch/arm/mpu/p2m.c
@@ -135,11 +135,79 @@ int p2m_set_entry(struct p2m_domain *p2m, gfn_t sgfn, 
unsigned long nr,
     return __p2m_set_entry(p2m, sgfn, nr, smfn, t, a);
 }
 
-mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn, p2m_type_t *t,
-                    p2m_access_t *a, unsigned int *page_order, bool *valid)
+/*
+ * Get the details of guest MPU memory region [gfn, gfn + nr_gfns).
+ *
+ * If the region is mapped, `t` is set to the p2m_type of the region and the
+ * starting MFN is returned.
+ * If the region is not mapped, INVALID_MFN is returned.
+ */
+static mfn_t p2m_get_mpu_region(struct p2m_domain *p2m, gfn_t gfn,
+                                unsigned long nr_gfns, p2m_type_t *type,
+                                bool *valid)
 {
-    BUG_ON("unimplemented");
-    return INVALID_MFN;
+    pr_t *table = NULL;
+    pr_t *region = NULL;
+    uint8_t idx = INVALID_REGION_IDX;
+    gfn_t egfn = gfn_add(gfn, nr_gfns);
+    p2m_type_t optional_type = p2m_invalid;
+    bool optional_valid = false;
+    mfn_t ret = INVALID_MFN;
+
+    ASSERT(p2m_is_locked(p2m));
+
+    /*
+     * Check if the ending gfn is higher than the highest the p2m map
+     * currently holds, or the starting gfn lower than the lowest it holds.
+     */
+    if ( (gfn_x(egfn) > gfn_x(p2m->max_mapped_gfn)) ||
+         (gfn_x(gfn) < gfn_x(p2m->lowest_mapped_gfn)) )
+        goto out;
+
+    table = (pr_t *)page_to_virt(p2m->root);
+    /* The table should always be non-NULL and is always present. */
+    if ( !table )
+        ASSERT_UNREACHABLE();
+
+    if ( is_gfns_mapped(table, p2m->nr_regions, gfn, nr_gfns, &idx) )
+        goto out;
+
+    region = &table[idx];
+    if ( region_is_p2m_valid(region) )
+    {
+        optional_type = region_get_p2m(region);
+        optional_valid = region_is_valid(region);
+    }
+
+    /* Always GFN == MFN on MPU systems. */
+    ret = _mfn(gfn_x(gfn));
+
+out:
+    if ( type )
+        *type = optional_type;
+
+    if ( valid )
+        *valid = optional_valid;
+
+    return ret;
+}
+
+/*
+ * Get the details of a given gfn.
+ *
+ * If the entry is present, the associated MFN will be returned and the
+ * p2m type gets filled up.
+ * If the entry is not present, INVALID_MFN will be returned
+ *
+ * The page_order is meaningless in MPU system, and we keep it here
+ * to be compatible with MMU system.
+ */
+mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn,
+                    p2m_type_t *t, p2m_access_t *a,
+                    unsigned int *page_order,
+                    bool *valid)
+{
+    return p2m_get_mpu_region(p2m, gfn, 1, t, valid);
 }
 
 void p2m_dump_info(struct domain *d)
-- 
2.34.1