[Xen-devel] [PATCH v7 5/5] x86/ioreq server: Synchronously reset outstanding p2m_ioreq_server entries when an ioreq server unmaps.

[Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>]

After an ioreq server has unmapped, the remaining p2m_ioreq_server
entries need to be reset back to p2m_ram_rw. This patch does this
synchronously by iterating the p2m table.

The synchronous resetting is necessary because we need to guarantee
the p2m table is clean before another ioreq server is mapped. And
since the sweeping of p2m table could be time consuming, it is done
with hypercall continuation.

Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
---
Cc: Paul Durrant <paul.durrant@xxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

changes in v1: 
  - This patch is splitted from patch 4 of last version.
  - According to comments from Jan: update the gfn_start for
    when use hypercall continuation to reset the p2m type.
  - According to comments from Jan: use min() to compare gfn_end
    and max mapped pfn in p2m_finish_type_change()
---
 xen/arch/x86/hvm/dm.c          | 43 +++++++++++++++++++++++++++++++++++++-----
 xen/arch/x86/mm/p2m.c          | 29 ++++++++++++++++++++++++++++
 xen/include/asm-x86/p2m.h      |  5 +++++
 xen/include/public/hvm/dm_op.h |  3 +--
 4 files changed, 73 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/hvm/dm.c b/xen/arch/x86/hvm/dm.c
index f97478b..a92d5d7 100644
--- a/xen/arch/x86/hvm/dm.c
+++ b/xen/arch/x86/hvm/dm.c
@@ -288,6 +288,7 @@ static int inject_event(struct domain *d,
     return 0;
 }
 
+#define DMOP_op_mask 0xff
 static int dm_op(domid_t domid,
                  unsigned int nr_bufs,
                  xen_dm_op_buf_t bufs[])
@@ -315,10 +316,8 @@ static int dm_op(domid_t domid,
     }
 
     rc = -EINVAL;
-    if ( op.pad )
-        goto out;
 
-    switch ( op.op )
+    switch ( op.op & DMOP_op_mask )
     {
     case XEN_DMOP_create_ioreq_server:
     {
@@ -387,6 +386,10 @@ static int dm_op(domid_t domid,
     {
         const struct xen_dm_op_map_mem_type_to_ioreq_server *data =
             &op.u.map_mem_type_to_ioreq_server;
+        unsigned long gfn_start = op.op & ~DMOP_op_mask;
+        unsigned long gfn_end;
+
+        const_op = false;
 
         rc = -EINVAL;
         if ( data->pad )
@@ -396,8 +399,38 @@ static int dm_op(domid_t domid,
         if ( !hap_enabled(d) )
             break;
 
-        rc = hvm_map_mem_type_to_ioreq_server(d, data->id,
-                                              data->type, data->flags);
+        if ( gfn_start == 0 )
+            rc = hvm_map_mem_type_to_ioreq_server(d, data->id,
+                                                  data->type, data->flags);
+        /*
+         * Iterate p2m table when an ioreq server unmaps from p2m_ioreq_server,
+         * and reset the remaining p2m_ioreq_server entries back to p2m_ram_rw.
+         */
+        if ( (gfn_start > 0) || (data->flags == 0 && rc == 0) )
+        {
+            struct p2m_domain *p2m = p2m_get_hostp2m(d);
+
+            while ( read_atomic(&p2m->ioreq.entry_count) &&
+                    gfn_start <= p2m->max_mapped_pfn )
+            {
+                gfn_end = gfn_start + DMOP_op_mask;
+
+                p2m_finish_type_change(d, gfn_start, gfn_end,
+                                       p2m_ioreq_server, p2m_ram_rw);
+
+                gfn_start = gfn_end + 1;
+
+                /* Check for continuation if it's not the last iteration. */
+                if ( gfn_start <= p2m->max_mapped_pfn &&
+                     hypercall_preempt_check() )
+                {
+                    rc = -ERESTART;
+                    op.op |= gfn_start;
+                    break;
+                }
+            }
+        }
+
         break;
     }
 
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 94d7141..9a81f00 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1038,6 +1038,35 @@ void p2m_change_type_range(struct domain *d,
     p2m_unlock(p2m);
 }
 
+/* Synchronously modify the p2m type of a range of gfns from ot to nt. */
+void p2m_finish_type_change(struct domain *d,
+                            unsigned long start, unsigned long end,
+                            p2m_type_t ot, p2m_type_t nt)
+{
+    struct p2m_domain *p2m = p2m_get_hostp2m(d);
+    p2m_type_t t;
+    unsigned long gfn = start;
+
+    ASSERT(start <= end);
+    ASSERT(ot != nt);
+    ASSERT(p2m_is_changeable(ot) && p2m_is_changeable(nt));
+
+    p2m_lock(p2m);
+
+    end = min(end, p2m->max_mapped_pfn);
+    while ( gfn <= end )
+    {
+        get_gfn_query_unlocked(d, gfn, &t);
+
+        if ( t == ot )
+            p2m_change_type_one(d, gfn, t, nt);
+
+        gfn++;
+    }
+
+    p2m_unlock(p2m);
+}
+
 /*
  * Returns:
  *    0              for success
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 395f125..3eadd89 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -611,6 +611,11 @@ void p2m_change_type_range(struct domain *d,
 int p2m_change_type_one(struct domain *d, unsigned long gfn,
                         p2m_type_t ot, p2m_type_t nt);
 
+/* Synchronously change types across a range of p2m entries (start ... end) */
+void p2m_finish_type_change(struct domain *d,
+                            unsigned long start, unsigned long end,
+                            p2m_type_t ot, p2m_type_t nt);
+
 /* Report a change affecting memory types. */
 void p2m_memory_type_changed(struct domain *d);
 
diff --git a/xen/include/public/hvm/dm_op.h b/xen/include/public/hvm/dm_op.h
index c643b67..23b364b 100644
--- a/xen/include/public/hvm/dm_op.h
+++ b/xen/include/public/hvm/dm_op.h
@@ -343,8 +343,7 @@ struct xen_dm_op_map_mem_type_to_ioreq_server {
 };
 
 struct xen_dm_op {
-    uint32_t op;
-    uint32_t pad;
+    uint64_t op;
     union {
         struct xen_dm_op_create_ioreq_server create_ioreq_server;
         struct xen_dm_op_get_ioreq_server_info get_ioreq_server_info;
-- 
1.9.1


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