[PATCH RFCv2 10/15] xen/arm: mm: Allocate xen page tables in domheap rather than xenheap

[Julien Grall <julien@xen.org>]

From: Julien Grall <jgrall@amazon.com>

xen_{un,}map_table() already uses the helper to map/unmap pages
on-demand (note this is currently a NOP on arm64). So switching to
domheap don't have any disavantage.

But this as the benefit:
    - to keep the page tables unmapped if an arch decided to do so
    - reduce xenheap use on arm32 which can be pretty small

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

---
    Changes in v2:
        - New patch
---
 xen/arch/arm/mm.c | 36 +++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 19ecf73542ce..ae5a07ea956b 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -969,21 +969,6 @@ void *ioremap(paddr_t pa, size_t len)
     return ioremap_attr(pa, len, PAGE_HYPERVISOR_NOCACHE);
 }
 
-static int create_xen_table(lpae_t *entry)
-{
-    void *p;
-    lpae_t pte;
-
-    p = alloc_xenheap_page();
-    if ( p == NULL )
-        return -ENOMEM;
-    clear_page(p);
-    pte = mfn_to_xen_entry(virt_to_mfn(p), MT_NORMAL);
-    pte.pt.table = 1;
-    write_pte(entry, pte);
-    return 0;
-}
-
 static lpae_t *xen_map_table(mfn_t mfn)
 {
     /*
@@ -1024,6 +1009,27 @@ static void xen_unmap_table(const lpae_t *table)
     unmap_domain_page(table);
 }
 
+static int create_xen_table(lpae_t *entry)
+{
+    struct page_info *pg;
+    void *p;
+    lpae_t pte;
+
+    pg = alloc_domheap_page(NULL, 0);
+    if ( pg == NULL )
+        return -ENOMEM;
+
+    p = xen_map_table(page_to_mfn(pg));
+    clear_page(p);
+    xen_unmap_table(p);
+
+    pte = mfn_to_xen_entry(page_to_mfn(pg), MT_NORMAL);
+    pte.pt.table = 1;
+    write_pte(entry, pte);
+
+    return 0;
+}
+
 #define XEN_TABLE_MAP_FAILED 0
 #define XEN_TABLE_SUPER_PAGE 1
 #define XEN_TABLE_NORMAL_PAGE 2
-- 
2.17.1