[xen staging] xen: unpopulate memory when domain is static

[patchbot@xxxxxxx]

commit b01721f0779d56a60b9db26a09b79b469f260d8a
Author:     Penny Zheng <Penny.Zheng@xxxxxxx>
AuthorDate: Tue Sep 6 15:39:16 2022 +0800
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Tue Sep 6 17:53:35 2022 +0100

    xen: unpopulate memory when domain is static
    
    Today when a domain unpopulates the memory on runtime, they will always
    hand the memory back to the heap allocator. And it will be a problem if 
domain
    is static.
    
    Pages as guest RAM for static domain shall be reserved to only this domain
    and not be used for any other purposes, so they shall never go back to heap
    allocator.
    
    This commit puts reserved page on the new list resv_page_list after
    it has been freed.
    
    Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/common/domain.c     | 4 ++++
 xen/common/page_alloc.c | 7 +++++--
 xen/include/xen/sched.h | 3 +++
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 7062393e37..c23f449451 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -604,6 +604,10 @@ struct domain *domain_create(domid_t domid,
     INIT_PAGE_LIST_HEAD(&d->page_list);
     INIT_PAGE_LIST_HEAD(&d->extra_page_list);
     INIT_PAGE_LIST_HEAD(&d->xenpage_list);
+#ifdef CONFIG_STATIC_MEMORY
+    INIT_PAGE_LIST_HEAD(&d->resv_page_list);
+#endif
+
 
     spin_lock_init(&d->node_affinity_lock);
     d->node_affinity = NODE_MASK_ALL;
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 0c50dee4c5..26a2fad4e3 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2741,10 +2741,13 @@ void free_domstatic_page(struct page_info *page)
 
     drop_dom_ref = !domain_adjust_tot_pages(d, -1);
 
-    spin_unlock_recursive(&d->page_alloc_lock);
-
     free_staticmem_pages(page, 1, scrub_debug);
 
+    /* Add page on the resv_page_list *after* it has been freed. */
+    page_list_add_tail(page, &d->resv_page_list);
+
+    spin_unlock_recursive(&d->page_alloc_lock);
+
     if ( drop_dom_ref )
         put_domain(d);
 }
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 81f1fcba2a..557b3229f6 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -381,6 +381,9 @@ struct domain
     struct page_list_head page_list;  /* linked list */
     struct page_list_head extra_page_list; /* linked list (size extra_pages) */
     struct page_list_head xenpage_list; /* linked list (size xenheap_pages) */
+#ifdef CONFIG_STATIC_MEMORY
+    struct page_list_head resv_page_list; /* linked list */
+#endif
 
     /*
      * This field should only be directly accessed by domain_adjust_tot_pages()
--
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