[PATCH RFCv2 13/15] xen/arm: mm: Use the PMAP helpers in xen_{,un}map_table()

[Julien Grall <julien@xen.org>]

From: Julien Grall <jgrall@amazon.com>

During early boot, it is not possible to use xen_{,un}map_table()
if the page tables are not residing the Xen binary.

This is a blocker to switch some of the helpers to use xen_pt_update()
as we may need to allocate extra page tables and access them before
the domheap has been initialized (see setup_xenheap_mappings()).

xen_{,un}map_table() are now updated to use the PMAP helpers for early
boot map/unmap. Note that the special case for page-tables residing
in Xen binary has been dropped because it is "complex" and was
only added as a workaround in 8d4f1b8878e0 ("xen/arm: mm: Allow
generic xen page-tables helpers to be called early").

Signed-off-by: Julien Grall <jgrall@amazon.com>

---
    Changes in v2:
        - New patch
---
 xen/arch/arm/mm.c | 33 +++++++++------------------------
 1 file changed, 9 insertions(+), 24 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 5e713b599611..f5768f2d4a81 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -41,6 +41,7 @@
 #include <xen/sizes.h>
 #include <xen/libfdt/libfdt.h>
 
+#include <asm/pmap.h>
 #include <asm/setup.h>
 
 /* Override macros from asm/page.h to make them work with mfn_t */
@@ -967,27 +968,11 @@ void *ioremap(paddr_t pa, size_t len)
 static lpae_t *xen_map_table(mfn_t mfn)
 {
     /*
-     * We may require to map the page table before map_domain_page() is
-     * useable. The requirements here is it must be useable as soon as
-     * page-tables are allocated dynamically via alloc_boot_pages().
-     *
-     * We need to do the check on physical address rather than virtual
-     * address to avoid truncation on Arm32. Therefore is_kernel() cannot
-     * be used.
+     * During early boot, map_domain_page() may be unusable. Use the
+     * PMAP to map temporarily a page-table.
      */
     if ( system_state == SYS_STATE_early_boot )
-    {
-        if ( is_xen_fixed_mfn(mfn) )
-        {
-            /*
-             * It is fine to demote the type because the size of Xen
-             * will always fit in vaddr_t.
-             */
-            vaddr_t offset = mfn_to_maddr(mfn) - virt_to_maddr(&_start);
-
-            return (lpae_t *)(XEN_VIRT_START + offset);
-        }
-    }
+        return pmap_map(mfn);
 
     return map_domain_page(mfn);
 }
@@ -996,12 +981,12 @@ static void xen_unmap_table(const lpae_t *table)
 {
     /*
      * During early boot, xen_map_table() will not use map_domain_page()
-     * for page-tables residing in Xen binary. So skip the unmap part.
+     * but the PMAP.
      */
-    if ( system_state == SYS_STATE_early_boot && is_kernel(table) )
-        return;
-
-    unmap_domain_page(table);
+    if ( system_state == SYS_STATE_early_boot )
+        pmap_unmap(table);
+    else
+        unmap_domain_page(table);
 }
 
 static int create_xen_table(lpae_t *entry)
-- 
2.17.1