[PATCH v2 20/40] xen/mpu: plump early_fdt_map in MPU systems

[Penny Zheng <Penny.Zheng@xxxxxxx>]

In MPU system, device tree binary can be packed with Xen
image through CONFIG_DTB_FILE, or provided by bootloader through x0.

In MPU system, each section in xen.lds.S is PAGE_SIZE aligned.
So in order to not overlap with the previous BSS section, dtb section
should be made page-aligned too.
We add . = ALIGN(PAGE_SIZE); in the head of dtb section to make it happen.

In this commit, we map early FDT with a transient MPU memory region at
rear with REGION_HYPERVISOR_BOOT.

Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
---
 xen/arch/arm/include/asm/arm64/mpu.h |  5 +++
 xen/arch/arm/mm_mpu.c                | 63 +++++++++++++++++++++++++---
 xen/arch/arm/xen.lds.S               |  5 ++-
 3 files changed, 67 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/include/asm/arm64/mpu.h 
b/xen/arch/arm/include/asm/arm64/mpu.h
index fcde6ad0db..b85e420a90 100644
--- a/xen/arch/arm/include/asm/arm64/mpu.h
+++ b/xen/arch/arm/include/asm/arm64/mpu.h
@@ -45,18 +45,22 @@
  * [3:4] Execute Never
  * [5:6] Access Permission
  * [7]   Region Present
+ * [8]   Boot-only Region
  */
 #define _REGION_AI_BIT            0
 #define _REGION_XN_BIT            3
 #define _REGION_AP_BIT            5
 #define _REGION_PRESENT_BIT       7
+#define _REGION_BOOTONLY_BIT      8
 #define _REGION_XN                (2U << _REGION_XN_BIT)
 #define _REGION_RO                (2U << _REGION_AP_BIT)
 #define _REGION_PRESENT           (1U << _REGION_PRESENT_BIT)
+#define _REGION_BOOTONLY          (1U << _REGION_BOOTONLY_BIT)
 #define REGION_AI_MASK(x)         (((x) >> _REGION_AI_BIT) & 0x7U)
 #define REGION_XN_MASK(x)         (((x) >> _REGION_XN_BIT) & 0x3U)
 #define REGION_AP_MASK(x)         (((x) >> _REGION_AP_BIT) & 0x3U)
 #define REGION_RO_MASK(x)         (((x) >> _REGION_AP_BIT) & 0x2U)
+#define REGION_BOOTONLY_MASK(x)   (((x) >> _REGION_BOOTONLY_BIT) & 0x1U)
 
 /*
  * _REGION_NORMAL is convenience define. It is not meant to be used
@@ -68,6 +72,7 @@
 #define REGION_HYPERVISOR_RO      (_REGION_NORMAL|_REGION_XN|_REGION_RO)
 
 #define REGION_HYPERVISOR         REGION_HYPERVISOR_RW
+#define REGION_HYPERVISOR_BOOT    (REGION_HYPERVISOR_RW|_REGION_BOOTONLY)
 
 #define INVALID_REGION            (~0UL)
 
diff --git a/xen/arch/arm/mm_mpu.c b/xen/arch/arm/mm_mpu.c
index 08720a7c19..b34dbf4515 100644
--- a/xen/arch/arm/mm_mpu.c
+++ b/xen/arch/arm/mm_mpu.c
@@ -20,11 +20,16 @@
  */
 
 #include <xen/init.h>
+#include <xen/libfdt/libfdt.h>
 #include <xen/mm.h>
 #include <xen/page-size.h>
+#include <xen/pfn.h>
+#include <xen/sizes.h>
 #include <xen/spinlock.h>
 #include <asm/arm64/mpu.h>
+#include <asm/early_printk.h>
 #include <asm/page.h>
+#include <asm/setup.h>
 
 #ifdef NDEBUG
 static inline void
@@ -62,6 +67,8 @@ uint64_t __ro_after_init max_xen_mpumap;
 
 static DEFINE_SPINLOCK(xen_mpumap_lock);
 
+static paddr_t dtb_paddr;
+
 /* Write a MPU protection region */
 #define WRITE_PROTECTION_REGION(sel, pr, prbar_el2, prlar_el2) ({       \
     uint64_t _sel = sel;                                                \
@@ -403,7 +410,16 @@ static int xen_mpumap_update_entry(paddr_t base, paddr_t 
limit,
 
         /* During boot time, the default index is next_fixed_region_idx. */
         if ( system_state <= SYS_STATE_active )
-            idx = next_fixed_region_idx;
+        {
+            /*
+             * If it is a boot-only region (i.e. region for early FDT),
+             * it shall be added from the tail for late init re-organizing
+             */
+            if ( REGION_BOOTONLY_MASK(flags) )
+                idx = next_transient_region_idx;
+            else
+                idx = next_fixed_region_idx;
+        }
 
         xen_mpumap[idx] = pr_of_xenaddr(base, limit - 1, 
REGION_AI_MASK(flags));
         /* Set permission */
@@ -465,14 +481,51 @@ int map_pages_to_xen(unsigned long virt,
                              mfn_to_maddr(mfn_add(mfn, nr_mfns)), flags);
 }
 
-/* TODO: Implementation on the first usage */
-void dump_hyp_walk(vaddr_t addr)
+void * __init early_fdt_map(paddr_t fdt_paddr)
 {
+    void *fdt_virt;
+    uint32_t size;
+
+    /*
+     * Check whether the physical FDT address is set and meets the minimum
+     * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be at
+     * least 8 bytes so that we always access the magic and size fields
+     * of the FDT header after mapping the first chunk, double check if
+     * that is indeed the case.
+     */
+     BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
+     if ( !fdt_paddr || fdt_paddr % MIN_FDT_ALIGN )
+         return NULL;
+
+    dtb_paddr = fdt_paddr;
+    /*
+     * In MPU system, device tree binary can be packed with Xen image
+     * through CONFIG_DTB_FILE, or provided by bootloader through x0.
+     * Map FDT with a transient MPU memory region of MAX_FDT_SIZE.
+     * After that, we can do some magic check.
+     */
+    if ( map_pages_to_xen(round_pgdown(fdt_paddr),
+                          maddr_to_mfn(round_pgdown(fdt_paddr)),
+                          round_pgup(MAX_FDT_SIZE) >> PAGE_SHIFT,
+                          REGION_HYPERVISOR_BOOT) )
+        panic("Unable to map the device-tree.\n");
+
+    /* VA == PA */
+    fdt_virt = maddr_to_virt(fdt_paddr);
+
+    if ( fdt_magic(fdt_virt) != FDT_MAGIC )
+        return NULL;
+
+    size = fdt_totalsize(fdt_virt);
+    if ( size > MAX_FDT_SIZE )
+        return NULL;
+
+    return fdt_virt;
 }
 
-void * __init early_fdt_map(paddr_t fdt_paddr)
+/* TODO: Implementation on the first usage */
+void dump_hyp_walk(vaddr_t addr)
 {
-    return NULL;
 }
 
 void __init remove_early_mappings(void)
diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index 79965a3c17..0565e22a1f 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -218,7 +218,10 @@ SECTIONS
   _end = . ;
 
   /* Section for the device tree blob (if any). */
-  .dtb : { *(.dtb) } :text
+  .dtb : {
+      . = ALIGN(PAGE_SIZE);
+      *(.dtb)
+  } :text
 
   DWARF2_DEBUG_SECTIONS
 
-- 
2.25.1