[PATCH 04/16] xen/arm: mm: Don't open-code Xen PT update in remove_early_mappings()

[Julien Grall <julien@xen.org>]

From: Julien Grall <julien.grall@arm.com>

Now that xen_pt_update_entry() is able to deal with different mapping
size, we can replace the open-coding of the page-tables update by a call
to modify_xen_mappings().

As the function is not meant to fail, a BUG_ON() is added to check the
return.

Note that we don't use destroy_xen_mappings() because the helper doesn't
allow us to pass a flags. In theory we could add an extra parameter to
the function, however there are no other expected users. Hence why
modify_xen_mappings() is used.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Hongda Deng <Hongda.Heng@arm.com>

---
    Changes in v4:
        - Add Hongda's reviewed-by
        - Add a comment to explain what modify_xen_mappings() does.
        - Clarify in the commit message hwy modify_xen_mappings() is
          used rather than destroy_xen_mappings().

    Changes in v2:
        - Stay consistent with how function name are used in the commit
        message
        - Add my AWS signed-off-by
---
 xen/arch/arm/mm.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 747083d820dd..64a79d45b38c 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -614,11 +614,12 @@ void * __init early_fdt_map(paddr_t fdt_paddr)
 
 void __init remove_early_mappings(void)
 {
-    lpae_t pte = {0};
-    write_pte(xen_second + second_table_offset(BOOT_FDT_VIRT_START), pte);
-    write_pte(xen_second + second_table_offset(BOOT_FDT_VIRT_START + SZ_2M),
-              pte);
-    flush_xen_tlb_range_va(BOOT_FDT_VIRT_START, BOOT_FDT_SLOT_SIZE);
+    int rc;
+
+    /* destroy the _PAGE_BLOCK mapping */
+    rc = modify_xen_mappings(BOOT_FDT_VIRT_START, BOOT_FDT_VIRT_END,
+                             _PAGE_BLOCK);
+    BUG_ON(rc);
 }
 
 /*
-- 
2.32.0