From: Hongyan Xia <hongyxia@amazon.com>

When there is not an always-mapped direct map, xenheap allocations need
to be mapped and unmapped on-demand.

Signed-off-by: Hongyan Xia <hongyxia@amazon.com>
Signed-off-by: Julien Grall <jgrall@amazon.com>
Signed-off-by: Elias El Yandouzi <eliasely@amazon.com>

----

    I have left the call to map_pages_to_xen() and destroy_xen_mappings()
    in the split heap for now. I am not entirely convinced this is necessary
    because in that setup only the xenheap would be always mapped and
    this doesn't contain any guest memory (aside the grant-table).
    So map/unmapping for every allocation seems unnecessary.

    Changes in v4:
        * Call printk instead of dprintk()

    Changes in v2:
        * Fix remaining wrong indentation in alloc_xenheap_pages()

    Changes since Hongyan's version:
        * Rebase
        * Fix indentation in alloc_xenheap_pages()
        * Fix build for arm32

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index b0be246780b7..2cef521ad85a 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2243,6 +2243,7 @@ void init_xenheap_pages(paddr_t ps, paddr_t pe)
 void *alloc_xenheap_pages(unsigned int order, unsigned int memflags)
 {
     struct page_info *pg;
+    void *virt_addr;
 
     ASSERT_ALLOC_CONTEXT();
 
@@ -2251,17 +2252,36 @@ void *alloc_xenheap_pages(unsigned int order, unsigned int memflags)
     if ( unlikely(pg == NULL) )
         return NULL;
 
-    return page_to_virt(pg);
+    virt_addr = page_to_virt(pg);
+
+    if ( !has_directmap() &&
+         map_pages_to_xen((unsigned long)virt_addr, page_to_mfn(pg), 1UL << order,
+                          PAGE_HYPERVISOR) )
+    {
+        /* Failed to map xenheap pages. */
+        free_heap_pages(pg, order, false);
+        return NULL;
+    }
+
+    return virt_addr;
 }
 
 
 void free_xenheap_pages(void *v, unsigned int order)
 {
+    unsigned long va = (unsigned long)v & PAGE_MASK;
+
     ASSERT_ALLOC_CONTEXT();
 
     if ( v == NULL )
         return;
 
+    if ( !has_directmap() &&
+         destroy_xen_mappings(va, va + (PAGE_SIZE << order)) )
+        printk(XENLOG_WARNING,
+                "Error while destroying xenheap mappings at %p, order %u\n",
+                v, order);
+
     free_heap_pages(virt_to_page(v), order, false);
 }
 
@@ -2285,6 +2305,7 @@ void *alloc_xenheap_pages(unsigned int order, unsigned int memflags)
 {
     struct page_info *pg;
     unsigned int i;
+    void *virt_addr;
 
     ASSERT_ALLOC_CONTEXT();
 
@@ -2297,16 +2318,28 @@ void *alloc_xenheap_pages(unsigned int order, unsigned int memflags)
     if ( unlikely(pg == NULL) )
         return NULL;
 
+    virt_addr = page_to_virt(pg);
+
+    if ( !has_directmap() &&
+         map_pages_to_xen((unsigned long)virt_addr, page_to_mfn(pg), 1UL << order,
+                          PAGE_HYPERVISOR) )
+    {
+        /* Failed to map xenheap pages. */
+        free_domheap_pages(pg, order);
+        return NULL;
+    }
+
     for ( i = 0; i < (1u << order); i++ )
         pg[i].count_info |= PGC_xen_heap;
 
-    return page_to_virt(pg);
+    return virt_addr;
 }
 
 void free_xenheap_pages(void *v, unsigned int order)
 {
     struct page_info *pg;
     unsigned int i;
+    unsigned long va = (unsigned long)v & PAGE_MASK;
 
     ASSERT_ALLOC_CONTEXT();
 
@@ -2318,6 +2351,12 @@ void free_xenheap_pages(void *v, unsigned int order)
     for ( i = 0; i < (1u << order); i++ )
         pg[i].count_info &= ~PGC_xen_heap;
 
+    if ( !has_directmap() &&
+         destroy_xen_mappings(va, va + (PAGE_SIZE << order)) )
+        printk(XENLOG_WARNING
+                "Error while destroying xenheap mappings at %p, order %u\n",
+                v, order);
+
     free_heap_pages(pg, order, true);
 }
 
-- 
2.40.1