[PATCH v6 9/9] xen: retrieve reserved pages on populate_physmap

[Penny Zheng <Penny.Zheng@xxxxxxx>]

When a static domain populates memory through populate_physmap at runtime,
it shall retrieve reserved pages from resv_page_list to make sure that
guest RAM is still restricted in statically configured memory regions.
This commit also introduces a new helper acquire_reserved_page to make it work.

Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
---
v6 changes:
- drop the lock before returning
---
v5 changes:
- extract common codes for assigning pages into a helper assign_domstatic_pages
- refine commit message
- remove stub function acquire_reserved_page
- Alloc/free of memory can happen concurrently. So access to rsv_page_list
needs to be protected with a spinlock
---
v4 changes：
- miss dropping __init in acquire_domstatic_pages
- add the page back to the reserved list in case of error
- remove redundant printk
- refine log message and make it warn level
---
v3 changes:
- move is_domain_using_staticmem to the common header file
- remove #ifdef CONFIG_STATIC_MEMORY-ary
- remove meaningless page_to_mfn(page) in error log
---
v2 changes:
- introduce acquire_reserved_page to retrieve reserved pages from
resv_page_list
- forbid non-zero-order requests in populate_physmap
- let is_domain_static return ((void)(d), false) on x86
---
 xen/common/memory.c     | 23 ++++++++++++++
 xen/common/page_alloc.c | 70 +++++++++++++++++++++++++++++++----------
 xen/include/xen/mm.h    |  1 +
 3 files changed, 77 insertions(+), 17 deletions(-)

diff --git a/xen/common/memory.c b/xen/common/memory.c
index f2d009843a..cb330ce877 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -245,6 +245,29 @@ static void populate_physmap(struct memop_args *a)
 
                 mfn = _mfn(gpfn);
             }
+            else if ( is_domain_using_staticmem(d) )
+            {
+                /*
+                 * No easy way to guarantee the retrieved pages are contiguous,
+                 * so forbid non-zero-order requests here.
+                 */
+                if ( a->extent_order != 0 )
+                {
+                    gdprintk(XENLOG_WARNING,
+                             "Cannot allocate static order-%u pages for static 
%pd\n",
+                             a->extent_order, d);
+                    goto out;
+                }
+
+                mfn = acquire_reserved_page(d, a->memflags);
+                if ( mfn_eq(mfn, INVALID_MFN) )
+                {
+                    gdprintk(XENLOG_WARNING,
+                             "%pd: failed to retrieve a reserved page\n",
+                             d);
+                    goto out;
+                }
+            }
             else
             {
                 page = alloc_domheap_pages(d, a->extent_order, a->memflags);
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 9004dd41c1..57d28304df 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2661,9 +2661,8 @@ void free_staticmem_pages(struct page_info *pg, unsigned 
long nr_mfns,
     }
 }
 
-static bool __init prepare_staticmem_pages(struct page_info *pg,
-                                           unsigned long nr_mfns,
-                                           unsigned int memflags)
+static bool prepare_staticmem_pages(struct page_info *pg, unsigned long 
nr_mfns,
+                                    unsigned int memflags)
 {
     bool need_tlbflush = false;
     uint32_t tlbflush_timestamp = 0;
@@ -2744,21 +2743,9 @@ static struct page_info * __init 
acquire_staticmem_pages(mfn_t smfn,
     return pg;
 }
 
-/*
- * Acquire nr_mfns contiguous pages, starting at #smfn, of static memory,
- * then assign them to one specific domain #d.
- */
-int __init acquire_domstatic_pages(struct domain *d, mfn_t smfn,
-                                   unsigned int nr_mfns, unsigned int memflags)
+static int assign_domstatic_pages(struct domain *d, struct page_info *pg,
+                                  unsigned int nr_mfns, unsigned int memflags)
 {
-    struct page_info *pg;
-
-    ASSERT(!in_irq());
-
-    pg = acquire_staticmem_pages(smfn, nr_mfns, memflags);
-    if ( !pg )
-        return -ENOENT;
-
     if ( !d || (memflags & (MEMF_no_owner | MEMF_no_refcount)) )
     {
         /*
@@ -2777,6 +2764,55 @@ int __init acquire_domstatic_pages(struct domain *d, 
mfn_t smfn,
 
     return 0;
 }
+
+/*
+ * Acquire nr_mfns contiguous pages, starting at #smfn, of static memory,
+ * then assign them to one specific domain #d.
+ */
+int __init acquire_domstatic_pages(struct domain *d, mfn_t smfn,
+                                   unsigned int nr_mfns, unsigned int memflags)
+{
+    struct page_info *pg;
+
+    ASSERT(!in_irq());
+
+    pg = acquire_staticmem_pages(smfn, nr_mfns, memflags);
+    if ( !pg )
+        return -ENOENT;
+
+    if ( assign_domstatic_pages(d, pg, nr_mfns, memflags) )
+        return -EINVAL;
+
+    return 0;
+}
+
+/*
+ * Acquire a page from reserved page list(resv_page_list), when populating
+ * memory for static domain on runtime.
+ */
+mfn_t acquire_reserved_page(struct domain *d, unsigned int memflags)
+{
+    struct page_info *page;
+
+    spin_lock(&d->page_alloc_lock);
+    /* Acquire a page from reserved page list(resv_page_list). */
+    page = page_list_remove_head(&d->resv_page_list);
+    spin_unlock(&d->page_alloc_lock);
+    if ( unlikely(!page) )
+        return INVALID_MFN;
+
+    if ( !prepare_staticmem_pages(page, 1, memflags) )
+        goto fail;
+
+    if ( assign_domstatic_pages(d, page, 1, memflags) )
+        goto fail;
+
+    return page_to_mfn(page);
+
+ fail:
+    page_list_add_tail(page, &d->resv_page_list);
+    return INVALID_MFN;
+}
 #endif
 
 /*
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index e80b4bdcde..e100151e50 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -90,6 +90,7 @@ void free_staticmem_pages(struct page_info *pg, unsigned long 
nr_mfns,
                           bool need_scrub);
 int acquire_domstatic_pages(struct domain *d, mfn_t smfn, unsigned int nr_mfns,
                             unsigned int memflags);
+mfn_t acquire_reserved_page(struct domain *d, unsigned int memflags);
 
 /* Map machine page range in Xen virtual address space. */
 int map_pages_to_xen(
-- 
2.25.1