[v2] xen/page_alloc: Add a path for xenheap when there is no direct map

Commit Message

Elias El Yandouzi Jan. 16, 2024, 6:50 p.m. UTC

From: Hongyan Xia <[e-mail]>

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

Signed-off-by: Hongyan Xia <[e-mail]>
Signed-off-by: Julien Grall <[e-mail]>
Signed-off-by: Elias El Yandouzi <[e-mail]>

----

    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 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

Patch

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index a3746cfbcf..52934ec5c1 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2237,6 +2237,7 @@  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();
 
@@ -2245,17 +2246,36 @@  void *alloc_xenheap_pages(unsigned int order, unsigned int memflags)
     if ( unlikely(pg == NULL) )
         return NULL;
 
+    ret = page_to_virt(pg);
+
+    if ( !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 ( !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);
 }
 
@@ -2279,6 +2299,7 @@  void *alloc_xenheap_pages(unsigned int order, unsigned int memflags)
 {
     struct page_info *pg;
     unsigned int i;
+    void *ret;
 
     ASSERT_ALLOC_CONTEXT();
 
@@ -2291,16 +2312,28 @@  void *alloc_xenheap_pages(unsigned int order, unsigned int memflags)
     if ( unlikely(pg == NULL) )
         return NULL;
 
+    ret = page_to_virt(pg);
+
+    if ( !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();
 
@@ -2312,6 +2345,12 @@  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 + (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);
 }