[PATCH 15/22] xen/page_alloc: add a path for xenheap when there is no direct map

[Julien Grall <julien@xxxxxxx>]

From: Hongyan Xia <hongyxia@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>

----

    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 since Hongyan's version:
        * Rebase
        * Fix indentation in alloc_xenheap_pages()
        * Fix build for arm32
---
 xen/common/page_alloc.c | 41 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 0a950288e241..0c4af5a71407 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2222,6 +2222,7 @@ 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 *ret;
 
     ASSERT_ALLOC_CONTEXT();
 
@@ -2230,17 +2231,36 @@ void *alloc_xenheap_pages(unsigned int order, unsigned 
int memflags)
     if ( unlikely(pg == NULL) )
         return NULL;
 
+    ret = page_to_virt(pg);
+
+    if ( !arch_has_directmap() &&
+         map_pages_to_xen((unsigned long)ret, page_to_mfn(pg), 1UL << order,
+                          PAGE_HYPERVISOR) )
+        {
+            /* Failed to map xenheap pages. */
+            free_heap_pages(pg, order, false);
+            return NULL;
+        }
+
     return page_to_virt(pg);
 }
 
 
 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 ( !arch_has_directmap() &&
+         destroy_xen_mappings(va, va + (1UL << (order + PAGE_SHIFT))) )
+        dprintk(XENLOG_WARNING,
+                "Error while destroying xenheap mappings at %p, order %u\n",
+                v, order);
+
     free_heap_pages(virt_to_page(v), order, false);
 }
 
@@ -2264,6 +2284,7 @@ void *alloc_xenheap_pages(unsigned int order, unsigned 
int memflags)
 {
     struct page_info *pg;
     unsigned int i;
+    void *ret;
 
     ASSERT_ALLOC_CONTEXT();
 
@@ -2276,16 +2297,28 @@ void *alloc_xenheap_pages(unsigned int order, unsigned 
int memflags)
     if ( unlikely(pg == NULL) )
         return NULL;
 
+    ret = page_to_virt(pg);
+
+    if ( !arch_has_directmap() &&
+         map_pages_to_xen((unsigned long)ret, 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 ret;
 }
 
 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();
 
@@ -2297,6 +2330,12 @@ void free_xenheap_pages(void *v, unsigned int order)
     for ( i = 0; i < (1u << order); i++ )
         pg[i].count_info &= ~PGC_xen_heap;
 
+    if ( !arch_has_directmap() &&
+         destroy_xen_mappings(va, va + (1UL << (order + PAGE_SHIFT))) )
+        dprintk(XENLOG_WARNING,
+                "Error while destroying xenheap mappings at %p, order %u\n",
+                v, order);
+
     free_heap_pages(pg, order, true);
 }
 
-- 
2.38.1