[RFC XEN PATCH v4 14/41] x86_64/mm: allow customized location of extended frametable and M2P table

[Haozhong Zhang <haozhong.zhang@intel.com>]

As the existing data in PMEM region is persistent, Xen hypervisor has
no knowledge of which part is free to be used for the frame table and
M2P table of that PMEM region. Instead, we will allow users or system
admins to specify the location of those frame table and M2P table.
The location is not necessarily at the beginning of the PMEM region,
which is different from the case of hotplugged RAM.

This commit adds the support for a customized page allocation
function, which is used to allocate the memory for the frame table and
M2P table. No page free function is added, and we require that all
allocated pages can be reclaimed or has no effect out of
memory_add_common(), if memory_add_common() fails.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
---
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
---
 xen/arch/x86/x86_64/mm.c | 83 ++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 69 insertions(+), 14 deletions(-)

diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 90341267d9..36dcb3f1cb 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -106,13 +106,44 @@ struct mem_hotadd_info
     unsigned long cur;
 };
 
+struct mem_hotadd_alloc
+{
+    /*
+     * Allocate 2^PAGETABLE_ORDER pages.
+     *
+     * No free function is added right now, so we require that all
+     * allocated pages can be reclaimed easily or has no effect out of
+     * memory_add_common(), if memory_add_common() fails.
+     *
+     * For example, alloc_hotadd_mfn(), which is used in RAM hotplug,
+     * allocates pages from the hotplugged RAM. If memory_add_common()
+     * fails, the hotplugged RAM will not be available to Xen, so
+     * pages allocated by alloc_hotadd_mfns() will never be used and
+     * have no effect.
+     *
+     * Parameters:
+     *  opaque:   arguments of the allocator (depending on the implementation)
+     *
+     * Return:
+     *  On success, return MFN of the first page.
+     *  Otherwise, return mfn_x(INVALID_MFN).
+     */
+    unsigned long (*alloc_mfns)(void *opaque);
+
+    /*
+     * Additional arguments passed to @alloc_mfns().
+     */
+    void *opaque;
+};
+
 static int hotadd_mem_valid(unsigned long pfn, struct mem_hotadd_info *info)
 {
     return (pfn < info->epfn && pfn >= info->spfn);
 }
 
-static unsigned long alloc_hotadd_mfn(struct mem_hotadd_info *info)
+static unsigned long alloc_hotadd_mfn(void *opaque)
 {
+    struct mem_hotadd_info *info = opaque;
     unsigned mfn;
 
     ASSERT((info->cur + ( 1UL << PAGETABLE_ORDER) < info->epfn) &&
@@ -315,7 +346,8 @@ static void destroy_m2p_mapping(struct mem_hotadd_info *info)
  * spfn/epfn: the pfn ranges to be setup
  * free_s/free_e: the pfn ranges that is free still
  */
-static int setup_compat_m2p_table(struct mem_hotadd_info *info)
+static int setup_compat_m2p_table(struct mem_hotadd_info *info,
+                                  struct mem_hotadd_alloc *alloc)
 {
     unsigned long i, va, smap, emap, rwva, epfn = info->epfn, mfn;
     unsigned int n;
@@ -369,7 +401,13 @@ static int setup_compat_m2p_table(struct mem_hotadd_info *info)
         if ( n == CNT )
             continue;
 
-        mfn = alloc_hotadd_mfn(info);
+        mfn = alloc->alloc_mfns(alloc->opaque);
+        if ( mfn == mfn_x(INVALID_MFN) )
+        {
+            err = -ENOMEM;
+            break;
+        }
+
         err = map_pages_to_xen(rwva, mfn, 1UL << PAGETABLE_ORDER,
                                PAGE_HYPERVISOR);
         if ( err )
@@ -389,7 +427,8 @@ static int setup_compat_m2p_table(struct mem_hotadd_info *info)
  * Allocate and map the machine-to-phys table.
  * The L3 for RO/RWRW MPT and the L2 for compatible MPT should be setup already
  */
-static int setup_m2p_table(struct mem_hotadd_info *info)
+static int setup_m2p_table(struct mem_hotadd_info *info,
+                           struct mem_hotadd_alloc *alloc)
 {
     unsigned long i, va, smap, emap;
     unsigned int n;
@@ -438,7 +477,13 @@ static int setup_m2p_table(struct mem_hotadd_info *info)
                 break;
         if ( n < CNT )
         {
-            unsigned long mfn = alloc_hotadd_mfn(info);
+            unsigned long mfn = alloc->alloc_mfns(alloc->opaque);
+
+            if ( mfn == mfn_x(INVALID_MFN) )
+            {
+                ret = -ENOMEM;
+                goto error;
+            }
 
             ret = map_pages_to_xen(
                         RDWR_MPT_VIRT_START + i * sizeof(unsigned long),
@@ -483,7 +528,7 @@ static int setup_m2p_table(struct mem_hotadd_info *info)
 #undef CNT
 #undef MFN
 
-    ret = setup_compat_m2p_table(info);
+    ret = setup_compat_m2p_table(info, alloc);
 error:
     return ret;
 }
@@ -762,7 +807,7 @@ static void cleanup_frame_table(unsigned long spfn, unsigned long epfn)
 }
 
 static int setup_frametable_chunk(void *start, void *end,
-                                  struct mem_hotadd_info *info)
+                                  struct mem_hotadd_alloc *alloc)
 {
     unsigned long s = (unsigned long)start;
     unsigned long e = (unsigned long)end;
@@ -774,7 +819,13 @@ static int setup_frametable_chunk(void *start, void *end,
 
     for ( cur = s; cur < e; cur += (1UL << L2_PAGETABLE_SHIFT) )
     {
-        mfn = alloc_hotadd_mfn(info);
+        mfn = alloc->alloc_mfns(alloc->opaque);
+        if ( mfn == mfn_x(INVALID_MFN) )
+        {
+            err = -ENOMEM;
+            break;
+        }
+
         err = map_pages_to_xen(cur, mfn, 1UL << PAGETABLE_ORDER,
                                PAGE_HYPERVISOR);
         if ( err )
@@ -789,7 +840,8 @@ static int setup_frametable_chunk(void *start, void *end,
     return err;
 }
 
-static int extend_frame_table(struct mem_hotadd_info *info)
+static int extend_frame_table(struct mem_hotadd_info *info,
+                              struct mem_hotadd_alloc *alloc)
 {
     unsigned long cidx, nidx, eidx, spfn, epfn;
     int err = 0;
@@ -816,7 +868,7 @@ static int extend_frame_table(struct mem_hotadd_info *info)
             nidx = eidx;
         err = setup_frametable_chunk(pdx_to_page(cidx * PDX_GROUP_COUNT ),
                                      pdx_to_page(nidx * PDX_GROUP_COUNT),
-                                     info);
+                                     alloc);
         if ( err )
             break;
 
@@ -1338,7 +1390,8 @@ static int mem_hotadd_check(unsigned long spfn, unsigned long epfn)
 }
 
 static int memory_add_common(struct mem_hotadd_info *info,
-                             unsigned int pxm, bool direct_map)
+                             unsigned int pxm, bool direct_map,
+                             struct mem_hotadd_alloc *alloc)
 {
     unsigned long spfn = info->spfn, epfn = info->epfn;
     int ret;
@@ -1402,7 +1455,7 @@ static int memory_add_common(struct mem_hotadd_info *info,
             NODE_DATA(node)->node_spanned_pages = epfn - node_start_pfn(node);
     }
 
-    ret = extend_frame_table(info);
+    ret = extend_frame_table(info, alloc);
     if ( ret )
         goto restore_node_status;
 
@@ -1415,7 +1468,7 @@ static int memory_add_common(struct mem_hotadd_info *info,
     total_pages += epfn - spfn;
 
     set_pdx_range(spfn, epfn);
-    ret = setup_m2p_table(info);
+    ret = setup_m2p_table(info, alloc);
 
     if ( ret )
         goto destroy_m2p;
@@ -1465,11 +1518,13 @@ destroy_directmap:
 int memory_add(unsigned long spfn, unsigned long epfn, unsigned int pxm)
 {
     struct mem_hotadd_info info = { .spfn = spfn, .epfn = epfn, .cur = spfn };
+    struct mem_hotadd_alloc alloc =
+        { .alloc_mfns = alloc_hotadd_mfn, .opaque = &info };
     int ret;
 
     dprintk(XENLOG_INFO, "memory_add %lx ~ %lx with pxm %x\n", spfn, epfn, pxm);
 
-    ret = memory_add_common(&info, pxm, true);
+    ret = memory_add_common(&info, pxm, true, &alloc);
     if ( !ret )
     {
         /* We can't revert any more */
-- 
2.15.1


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