[PATCH v5 6/7] xen/arm: introduce acquire_staticmem_pages and acquire_domstatic_pages

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

acquire_staticmem_pages aims to acquire nr_mfns contiguous pages of
static memory, starting at smfn. And it is the equivalent of alloc_heap_pages
for 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 pages of static memory,
then on success, it will use assign_pages to assign those pages
to one specific domain.

In order to differentiate pages of static memory from those allocated from
heap, this patch introduces a new page flag PGC_reserved, then mark pages of
static memory PGC_reserved when initializing them.

Signed-off-by: Penny Zheng <penny.zheng@arm.com>
---
v5 changes
- bundle all the functions for static allocation in a single place
- return an error and revert the changes, when the page is not free
and reserved.
- check the MFN is valid for every page and also add a comment to warn
that this function needs to be reworked if used outside of boot.
- use less of mfn_to_page/page_to_mfn
- use ASSERT_UNREACHABLE() to also check that the two flags are clear
- pass the start MFN first and then the number of pages in both
acquire_staticmem_pages and acquire_domstatic_pages
- make acquire_domstatic_pages() to return an errno
- combine the commit of "xen/arm: introduce PGC_reserved"
---
 xen/common/page_alloc.c  | 118 ++++++++++++++++++++++++++++++++++++++-
 xen/include/asm-arm/mm.h |   3 +
 xen/include/xen/mm.h     |   2 +
 3 files changed, 121 insertions(+), 2 deletions(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 05c9834dc2..c0a8898502 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 PGC_reserved
+#define PGC_reserved 0
+#endif
+
 /*
  * Comma-separated list of hexadecimal page numbers containing bad bytes.
  * e.g. 'badpage=0x3f45,0x8a321'.
@@ -2282,7 +2286,7 @@ 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++;
         }
@@ -2321,7 +2325,8 @@ 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]));
     }
 
@@ -2625,7 +2630,116 @@ void __init free_staticmem_pages(struct page_info *pg, unsigned long nr_mfns,
             /* TODO: asynchronous scrubbing for pages of static memory. */
             scrub_one_page(pg);
         }
+
+        /* In case initializing page of static memory, mark it PGC_reserved. */
+        pg[i].count_info |= PGC_reserved;
+    }
+}
+
+/*
+ * Acquire nr_mfns contiguous reserved pages, starting at #smfn, of
+ * static memory.
+ * This function needs to be reworked if used outside of boot.
+ */
+static struct page_info * __init acquire_staticmem_pages(mfn_t smfn,
+                                                         unsigned long nr_mfns,
+                                                         unsigned int memflags)
+{
+    bool need_tlbflush = false;
+    uint32_t tlbflush_timestamp = 0;
+    unsigned long i;
+    struct page_info *pg;
+
+    ASSERT(nr_mfns);
+    for ( unsigned long i = 0; i < nr_mfns; i++ )
+        if ( !mfn_valid(mfn_add(smfn, i)) )
+            return NULL;
+
+    pg = mfn_to_page(smfn);
+
+    spin_lock(&heap_lock);
+
+    for ( i = 0; i < nr_mfns; i++ )
+    {
+        /* The page should be reserved and not yet allocated. */
+        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(smfn) + i,
+                   pg[i].count_info, pg[i].tlbflush_timestamp);
+            goto out_err;
+        }
+
+        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;
+
+out_err:
+    for ( unsigned long j = 0; j < i; j++ )
+        pg[j].count_info = PGC_reserved | PGC_state_free;
+
+    spin_unlock(&heap_lock);
+
+    return NULL;
+}
+
+/*
+ * 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 long 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)) )
+    {
+        /*
+         * Respective handling omitted here because right now
+         * acquired static memory is only for guest RAM.
+         */
+        ASSERT_UNREACHABLE();
+        return -EINVAL;
+    }
+
+    if ( assign_pages(d, pg, nr_mfns, memflags) )
+    {
+        free_staticmem_pages(pg, nr_mfns, memflags & MEMF_no_scrub);
+        return -EINVAL;
+    }
+
+    return 0;
 }
 #endif
 
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index ded74d29da..7b5e7b7f69 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -108,6 +108,9 @@ struct page_info
   /* Page is Xen heap? */
 #define _PGC_xen_heap     PG_shift(2)
 #define PGC_xen_heap      PG_mask(1, 2)
+  /* Page is reserved */
+#define _PGC_reserved     PG_shift(3)
+#define PGC_reserved      PG_mask(1, 3)
 /* ... */
 /* Page is broken? */
 #define _PGC_broken       PG_shift(7)
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index f243ff88d7..6d83b7894b 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -89,6 +89,8 @@ 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);
+int acquire_domstatic_pages(struct domain *d, mfn_t smfn, unsigned long nr_mfns,
+                            unsigned int memflags);
 #endif
 
 /* Map machine page range in Xen virtual address space. */
-- 
2.25.1