[PATCH V4 08/10] xen/arm: introduce acquire_staticmem_pages and acquire_domstatic_pages

[Penny Zheng <penny.zheng@arm.com>]

alloc_staticmem_pages aims to acquire nr_mfns contiguous pages of
static memory. And it is the equivalent of alloc_heap_pages for static
memory. Here only covers acquiring pre-configured static memory.

For each page, it shall check if the page is reserved(PGC_reserved)
and free. It shall also do a set of necessary initialization, which are
mostly the same ones in alloc_heap_pages, like, following the same
cache-coherency policy and turning page status into PGC_state_inuse, etc.

acquire_domstatic_pages is the equivalent of alloc_domheap_pages for
static memory, and it is to acquire nr_mfns contiguous pages of static memory
and assign them to one specific domain.

It uses acquire_staticmem_pages to acquire nr_mfns pre-configured pages of
static memory, then on success, it will use assign_pages to assign those pages
to one specific domain.

Signed-off-by: Penny Zheng <penny.zheng@arm.com>
---
v4 change:
- moving tlb/cache flush outside of the locked region, considering XSA-364
and reducing the amount of work happening with the heap_lock held
- remove MEMF_no_refcount case
- make acquire_staticmem_pages/acquire_domstatic_pages being __init
---
 xen/common/page_alloc.c | 108 +++++++++++++++++++++++++++++++++++++++-
 xen/include/xen/mm.h    |   3 ++
 2 files changed, 109 insertions(+), 2 deletions(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index e279c6f713..b0edaf12b3 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -151,6 +151,10 @@
 #define p2m_pod_offline_or_broken_replace(pg) BUG_ON(pg != NULL)
 #endif
 
+#ifndef CONFIG_STATIC_MEMORY
+#define PGC_reserved 0
+#endif
+
 /*
  * Comma-separated list of hexadecimal page numbers containing bad bytes.
  * e.g. 'badpage=0x3f45,0x8a321'.
@@ -1065,6 +1069,73 @@ static struct page_info *alloc_heap_pages(
     return pg;
 }
 
+#ifdef CONFIG_STATIC_MEMORY
+/*
+ * Acquire nr_mfns contiguous reserved pages, starting at #smfn, of
+ * static memory.
+ */
+static struct page_info * __init acquire_staticmem_pages(unsigned long nr_mfns,
+                                                         mfn_t smfn,
+                                                         unsigned int memflags)
+{
+    bool need_tlbflush = false;
+    uint32_t tlbflush_timestamp = 0;
+    unsigned long i;
+    struct page_info *pg;
+
+    /* For now, it only supports pre-configured static memory. */
+    if ( !mfn_valid(smfn) || !nr_mfns )
+        return NULL;
+
+    spin_lock(&heap_lock);
+
+    pg = mfn_to_page(smfn);
+
+    for ( i = 0; i < nr_mfns; i++ )
+    {
+        /*
+         * Reference count must continuously be zero for free pages
+         * of static memory(PGC_reserved).
+         */
+        if ( pg[i].count_info != (PGC_state_free | PGC_reserved) )
+        {
+            printk(XENLOG_ERR
+                   "pg[%lu] Static MFN %"PRI_mfn" c=%#lx t=%#x\n",
+                   i, mfn_x(page_to_mfn(pg + i)),
+                   pg[i].count_info, pg[i].tlbflush_timestamp);
+            BUG();
+        }
+
+        if ( !(memflags & MEMF_no_tlbflush) )
+            accumulate_tlbflush(&need_tlbflush, &pg[i],
+                                &tlbflush_timestamp);
+
+        /*
+         * Preserve flag PGC_reserved and change page state
+         * to PGC_state_inuse.
+         */
+        pg[i].count_info = (PGC_reserved | PGC_state_inuse);
+        /* Initialise fields which have other uses for free pages. */
+        pg[i].u.inuse.type_info = 0;
+        page_set_owner(&pg[i], NULL);
+    }
+
+    spin_unlock(&heap_lock);
+
+    if ( need_tlbflush )
+        filtered_flush_tlb_mask(tlbflush_timestamp);
+
+    /*
+     * Ensure cache and RAM are consistent for platforms where the guest
+     * can control its own visibility of/through the cache.
+     */
+    for ( i = 0; i < nr_mfns; i++ )
+        flush_page_to_ram(mfn_x(smfn) + i, !(memflags & MEMF_no_icache_flush));
+
+    return pg;
+}
+#endif
+
 /* Remove any offlined page in the buddy pointed to by head. */
 static int reserve_offlined_page(struct page_info *head)
 {
@@ -2306,7 +2377,7 @@ int assign_pages(
 
         for ( i = 0; i < nr; i++ )
         {
-            ASSERT(!(pg[i].count_info & ~PGC_extra));
+            ASSERT(!(pg[i].count_info & ~(PGC_extra | PGC_reserved)));
             if ( pg[i].count_info & PGC_extra )
                 extra_pages++;
         }
@@ -2345,7 +2416,8 @@ int assign_pages(
         page_set_owner(&pg[i], d);
         smp_wmb(); /* Domain pointer must be visible before updating refcnt. */
         pg[i].count_info =
-            (pg[i].count_info & PGC_extra) | PGC_allocated | 1;
+            (pg[i].count_info & (PGC_extra | PGC_reserved)) | PGC_allocated | 1;
+
         page_list_add_tail(&pg[i], page_to_list(d, &pg[i]));
     }
 
@@ -2411,6 +2483,38 @@ struct page_info *alloc_domheap_pages(
     return pg;
 }
 
+#ifdef CONFIG_STATIC_MEMORY
+/*
+ * Acquire nr_mfns contiguous pages, starting at #smfn, of static memory,
+ * then assign them to one specific domain #d.
+ */
+struct page_info * __init acquire_domstatic_pages(struct domain *d,
+                                                  unsigned long nr_mfns,
+                                                  mfn_t smfn, unsigned int memflags)
+{
+    struct page_info *pg = NULL;
+
+    ASSERT(!in_irq());
+
+    pg = acquire_staticmem_pages(nr_mfns, smfn, memflags);
+    if ( !pg )
+        return NULL;
+
+    /*
+     * MEMF_no_owner/MEMF_no_refcount cases are missing here because
+     * right now, acquired static memory is only for guest RAM.
+     */
+    ASSERT(d);
+    if ( assign_pages(pg, nr_mfns, d, memflags) )
+    {
+        free_staticmem_pages(pg, nr_mfns, memflags & MEMF_no_scrub);
+        return NULL;
+    }
+
+    return pg;
+}
+#endif
+
 void free_domheap_pages(struct page_info *pg, unsigned int order)
 {
     struct domain *d = page_get_owner(pg);
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index 2e75cdcbb7..62e8e2ad61 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -89,6 +89,9 @@ bool scrub_free_pages(void);
 /* These functions are for static memory */
 void free_staticmem_pages(struct page_info *pg, unsigned long nr_mfns,
                           bool need_scrub);
+struct page_info *acquire_domstatic_pages(struct domain *d,
+                                          unsigned long nr_mfns, mfn_t smfn,
+                                          unsigned int memflags);
 #endif
 
 /* Map machine page range in Xen virtual address space. */
-- 
2.25.1