xen/arm: Don't use copy_from_paddr for DTB relocation

Currently the early stage of the Arm boot maps the DTB using
early_fdt_map() using PAGE_HYPERVISOR_RO which is cacheable
read-only memory, later during DTB relocation the function
copy_from_paddr() is used to map pages in the same range on
the fixmap but using PAGE_HYPERVISOR_WC which is non-cacheable
read-write memory.

The Arm specifications, ARM DDI0487L.a, section B2.11 "Mismatched
memory attributes" discourage using mismatched attributes for
aliases of the same location.

Given that there is nothing preventing the relocation since the region
is already mapped, fix that by open-coding copy_from_paddr inside
relocate_fdt, without mapping on the fixmap.

Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index c1f2d1b89d4317224bb1011e0db3a7372df807e2..ffcae900d72e7da19482515c954441fab443a018 100644 (file)
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -237,16 +237,17 @@ void __init discard_initial_modules(void)
 }
 
 /* Relocate the FDT in Xen heap */
-static void * __init relocate_fdt(paddr_t dtb_paddr, size_t dtb_size)
+static void __init relocate_fdt(const void **dtb_vaddr, size_t dtb_size)
 {
     void *fdt = xmalloc_bytes(dtb_size);
 
     if ( !fdt )
         panic("Unable to allocate memory for relocating the Device-Tree.\n");
 
-    copy_from_paddr(fdt, dtb_paddr, dtb_size);
+    memcpy(fdt, *dtb_vaddr, dtb_size);
+    clean_dcache_va_range(fdt, dtb_size);
 
-    return fdt;
+    *dtb_vaddr = fdt;
 }
 
 void __init init_pdx(void)
@@ -362,7 +363,7 @@ void asmlinkage __init start_xen(unsigned long fdt_paddr)
     if ( acpi_disabled )
     {
         printk("Booting using Device Tree\n");
-        device_tree_flattened = relocate_fdt(fdt_paddr, fdt_size);
+        relocate_fdt(&device_tree_flattened, fdt_size);
         dt_unflatten_host_device_tree();
     }
     else