arm/mpu: Populate a new region in Xen MPU mapping table

Introduce map_pages_to_xen() that is implemented using a new helper,
xen_mpumap_update(), which is responsible for updating Xen MPU memory
mapping table(xen_mpumap), including creating a new entry, updating
or destroying an existing one, it is equivalent to xen_pt_update in MMU.

This commit only implements populating a new entry in Xen MPU memory mapping
table(xen_mpumap).

Signed-off-by: Penny Zheng <penny.zheng@arm.com>
Signed-off-by: Wei Chen <wei.chen@arm.com>
Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
Signed-off-by: Hari Limaye <hari.limaye@arm.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

xen/arch/arm/include/asm/mpu/mm.h

@@ -64,6 +64,7 @@ static inline void context_sync_mpu(void)
  * The following API requires context_sync_mpu() after being used to modify MPU
  * regions:
  *  - write_protection_region
+ *  - xen_mpumap_update
  */
 
 /* Reads the MPU region (into @pr_read) with index @sel from the HW */
@@ -72,6 +73,17 @@ void read_protection_region(pr_t *pr_read, uint8_t sel);
 /* Writes the MPU region (from @pr_write) with index @sel to the HW */
 void write_protection_region(const pr_t *pr_write, uint8_t sel);
 
+/*
+ * Maps an address range into the MPU data structure and updates the HW.
+ * Equivalent to xen_pt_update in an MMU system.
+ *
+ * @param base      Base address of the range to map (inclusive).
+ * @param limit     Limit address of the range to map (exclusive).
+ * @param flags     Flags for the memory range to map.
+ * @return          0 on success, negative on error.
+ */
+int xen_mpumap_update(paddr_t base, paddr_t limit, unsigned int flags);
+
 /*
  * Creates a pr_t structure describing a protection region.
  *

xen/arch/arm/mpu/mm.c

@@ -6,6 +6,7 @@
 #include <xen/lib.h>
 #include <xen/mm.h>
 #include <xen/sizes.h>
+#include <xen/spinlock.h>
 #include <xen/types.h>
 #include <asm/mpu.h>
 #include <asm/mpu/mm.h>
@@ -29,6 +30,8 @@ DECLARE_BITMAP(xen_mpumap_mask, MAX_MPU_REGION_NR) \
 /* EL2 Xen MPU memory region mapping table. */
 pr_t __cacheline_aligned __section(".data") xen_mpumap[MAX_MPU_REGION_NR];
 
+static DEFINE_SPINLOCK(xen_mpumap_lock);
+
 static void __init __maybe_unused build_assertions(void)
 {
     /*
@@ -165,6 +168,106 @@ int mpumap_contains_region(pr_t *table, uint8_t nr_regions, paddr_t base,
     return MPUMAP_REGION_NOTFOUND;
 }
 
+/*
+ * Allocate an entry for a new EL2 MPU region in the bitmap xen_mpumap_mask.
+ * @param idx   Set to the index of the allocated EL2 MPU region on success.
+ * @return      0 on success, otherwise -ENOENT on failure.
+ */
+static int xen_mpumap_alloc_entry(uint8_t *idx)
+{
+    ASSERT(spin_is_locked(&xen_mpumap_lock));
+
+    *idx = find_first_zero_bit(xen_mpumap_mask, max_mpu_regions);
+    if ( *idx == max_mpu_regions )
+    {
+        printk(XENLOG_ERR "EL2 MPU memory region mapping pool exhausted\n");
+        return -ENOENT;
+    }
+
+    set_bit(*idx, xen_mpumap_mask);
+
+    return 0;
+}
+
+/*
+ * Update the entry in the MPU memory region mapping table (xen_mpumap) for the
+ * given memory range and flags, creating one if none exists.
+ *
+ * @param base  Base address (inclusive).
+ * @param limit Limit address (exclusive).
+ * @param flags Region attributes (a combination of PAGE_HYPERVISOR_XXX)
+ * @return      0 on success, otherwise negative on error.
+ */
+static int xen_mpumap_update_entry(paddr_t base, paddr_t limit,
+                                   unsigned int flags)
+{
+    uint8_t idx;
+    int rc;
+
+    ASSERT(spin_is_locked(&xen_mpumap_lock));
+
+    /* Currently only region creation is supported. */
+    if ( !(flags & _PAGE_PRESENT) )
+        return -EINVAL;
+
+    rc = mpumap_contains_region(xen_mpumap, max_mpu_regions, base, limit, &idx);
+    if ( rc != MPUMAP_REGION_NOTFOUND )
+        return -EINVAL;
+
+    /* We are inserting a mapping => Create new region. */
+    rc = xen_mpumap_alloc_entry(&idx);
+    if ( rc )
+        return -ENOENT;
+
+    xen_mpumap[idx] = pr_of_addr(base, limit, flags);
+
+    write_protection_region(&xen_mpumap[idx], idx);
+
+    return 0;
+}
+
+int xen_mpumap_update(paddr_t base, paddr_t limit, unsigned int flags)
+{
+    int rc;
+
+    if ( flags_has_rwx(flags) )
+    {
+        printk("Mappings should not be both Writeable and Executable\n");
+        return -EINVAL;
+    }
+
+    if ( base >= limit )
+    {
+        printk("Base address %#"PRIpaddr" must be smaller than limit address %#"PRIpaddr"\n",
+               base, limit);
+        return -EINVAL;
+    }
+
+    if ( !IS_ALIGNED(base, PAGE_SIZE) || !IS_ALIGNED(limit, PAGE_SIZE) )
+    {
+        printk("base address %#"PRIpaddr", or limit address %#"PRIpaddr" is not page aligned\n",
+               base, limit);
+        return -EINVAL;
+    }
+
+    spin_lock(&xen_mpumap_lock);
+
+    rc = xen_mpumap_update_entry(base, limit, flags);
+    if ( !rc )
+        context_sync_mpu();
+
+    spin_unlock(&xen_mpumap_lock);
+
+    return rc;
+}
+
+int map_pages_to_xen(unsigned long virt, mfn_t mfn, unsigned long nr_mfns,
+                     unsigned int flags)
+{
+    /* MPU systems have no translation, ma == va, so pass virt directly */
+    return xen_mpumap_update(virt, mfn_to_maddr(mfn_add(mfn, nr_mfns)), flags);
+}
+
 void __init setup_mm(void)
 {
     BUG_ON("unimplemented");