[xen staging] xen: do not free reserved memory into heap

[patchbot@xxxxxxx]

commit d58b6aef96968facad5867513fdca262c68d48a4
Author:     Penny Zheng <Penny.Zheng@xxxxxxx>
AuthorDate: Tue Sep 6 15:39:14 2022 +0800
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Tue Sep 6 17:53:34 2022 +0100

    xen: do not free reserved memory into heap
    
    Pages used as guest RAM for static domain, shall be reserved to this
    domain only.
    So in case reserved pages being used for other purpose, users
    shall not free them back to heap, even when last ref gets dropped.
    
    This commit introduces a new helper free_domstatic_page to free
    static page in runtime, and free_staticmem_pages will be called by it
    in runtime, so let's drop the __init flag.
    
    Wrapper #ifdef CONFIG_STATIC_MEMORY around function declaration(
    free_staticmem_pages, free_domstatic_page, etc) is kinds of redundant,
    so we decide to remove it here.
    
    Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/arch/arm/include/asm/mm.h |  6 +++++-
 xen/arch/arm/mm.c             |  5 ++++-
 xen/common/page_alloc.c       | 40 +++++++++++++++++++++++++++++++++++++---
 xen/include/xen/mm.h          |  3 +--
 4 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h
index da25251cda..749fbefa0c 100644
--- a/xen/arch/arm/include/asm/mm.h
+++ b/xen/arch/arm/include/asm/mm.h
@@ -121,9 +121,13 @@ struct page_info
   /* Page is Xen heap? */
 #define _PGC_xen_heap     PG_shift(2)
 #define PGC_xen_heap      PG_mask(1, 2)
-  /* Page is static memory */
+#ifdef CONFIG_STATIC_MEMORY
+/* Page is static memory */
 #define _PGC_static    PG_shift(3)
 #define PGC_static     PG_mask(1, 3)
+#else
+#define PGC_static     0
+#endif
 /* ... */
 /* Page is broken? */
 #define _PGC_broken       PG_shift(7)
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index c81c706c8b..7f5b317d3e 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1496,7 +1496,10 @@ void put_page(struct page_info *page)
 
     if ( unlikely((nx & PGC_count_mask) == 0) )
     {
-        free_domheap_page(page);
+        if ( unlikely(nx & PGC_static) )
+            free_domstatic_page(page);
+        else
+            free_domheap_page(page);
     }
 }
 
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index bfd4150be7..0c50dee4c5 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2694,12 +2694,14 @@ struct domain *get_pg_owner(domid_t domid)
 
 #ifdef CONFIG_STATIC_MEMORY
 /* Equivalent of free_heap_pages to free nr_mfns pages of static memory. */
-void __init free_staticmem_pages(struct page_info *pg, unsigned long nr_mfns,
-                                 bool need_scrub)
+void free_staticmem_pages(struct page_info *pg, unsigned long nr_mfns,
+                          bool need_scrub)
 {
     mfn_t mfn = page_to_mfn(pg);
     unsigned long i;
 
+    spin_lock(&heap_lock);
+
     for ( i = 0; i < nr_mfns; i++ )
     {
         mark_page_free(&pg[i], mfn_add(mfn, i));
@@ -2710,9 +2712,41 @@ void __init free_staticmem_pages(struct page_info *pg, 
unsigned long nr_mfns,
             scrub_one_page(pg);
         }
 
-        /* In case initializing page of static memory, mark it PGC_static. */
         pg[i].count_info |= PGC_static;
     }
+
+    spin_unlock(&heap_lock);
+}
+
+void free_domstatic_page(struct page_info *page)
+{
+    struct domain *d = page_get_owner(page);
+    bool drop_dom_ref;
+
+    if ( unlikely(!d) )
+    {
+        printk(XENLOG_G_ERR
+               "The about-to-free static page %"PRI_mfn" must be owned by a 
domain\n",
+               mfn_x(page_to_mfn(page)));
+        ASSERT_UNREACHABLE();
+        return;
+    }
+
+    ASSERT_ALLOC_CONTEXT();
+
+    /* NB. May recursively lock from relinquish_memory(). */
+    spin_lock_recursive(&d->page_alloc_lock);
+
+    arch_free_heap_page(d, page);
+
+    drop_dom_ref = !domain_adjust_tot_pages(d, -1);
+
+    spin_unlock_recursive(&d->page_alloc_lock);
+
+    free_staticmem_pages(page, 1, scrub_debug);
+
+    if ( drop_dom_ref )
+        put_domain(d);
 }
 
 /*
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index 35b065146f..deadf4b2a1 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -85,13 +85,12 @@ bool scrub_free_pages(void);
 } while ( false )
 #define FREE_XENHEAP_PAGE(p) FREE_XENHEAP_PAGES(p, 0)
 
-#ifdef CONFIG_STATIC_MEMORY
 /* These functions are for static memory */
 void free_staticmem_pages(struct page_info *pg, unsigned long nr_mfns,
                           bool need_scrub);
+void free_domstatic_page(struct page_info *page);
 int acquire_domstatic_pages(struct domain *d, mfn_t smfn, unsigned int nr_mfns,
                             unsigned int memflags);
-#endif
 
 /* Map machine page range in Xen virtual address space. */
 int map_pages_to_xen(
--
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