[Xen-devel] [PATCH v8 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 v2: 
  - According to comments from Jan and Andrew: do not use the
    HVMOP type hypercall continuation method. Instead, adding
    an opaque in xen_dm_op_map_mem_type_to_ioreq_server to
    store the gfn.
  - According to comments from Jan: change routine's comments
    and name of parameters of p2m_finish_type_change().

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     | 41 ++++++++++++++++++++++++++++++++++++++---
 xen/arch/x86/mm/p2m.c     | 29 +++++++++++++++++++++++++++++
 xen/include/asm-x86/p2m.h |  7 +++++++
 3 files changed, 74 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/hvm/dm.c b/xen/arch/x86/hvm/dm.c
index 1619feb..9e1e27b 100644
--- a/xen/arch/x86/hvm/dm.c
+++ b/xen/arch/x86/hvm/dm.c
@@ -385,16 +385,51 @@ static int dm_op(domid_t domid,
 
     case XEN_DMOP_map_mem_type_to_ioreq_server:
     {
-        const struct xen_dm_op_map_mem_type_to_ioreq_server *data =
+        struct xen_dm_op_map_mem_type_to_ioreq_server *data =
             &op.u.map_mem_type_to_ioreq_server;
+        unsigned long first_gfn = data->opaque;
+        unsigned long last_gfn;
+
+        const_op = false;
 
         rc = -EOPNOTSUPP;
         /* Only support for HAP enabled hvm. */
         if ( !hap_enabled(d) )
             break;
 
-        rc = hvm_map_mem_type_to_ioreq_server(d, data->id,
-                                              data->type, data->flags);
+        if ( first_gfn == 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 ( (first_gfn > 0) || (data->flags == 0 && rc == 0) )
+        {
+            struct p2m_domain *p2m = p2m_get_hostp2m(d);
+
+            while ( read_atomic(&p2m->ioreq.entry_count) &&
+                    first_gfn <= p2m->max_mapped_pfn )
+            {
+                /* Iterate p2m table for 256 gfns each time. */
+                last_gfn = first_gfn + 0xff;
+
+                p2m_finish_type_change(d, first_gfn, last_gfn,
+                                       p2m_ioreq_server, p2m_ram_rw);
+
+                first_gfn = last_gfn + 1;
+
+                /* Check for continuation if it's not the last iteration. */
+                if ( first_gfn <= p2m->max_mapped_pfn &&
+                     hypercall_preempt_check() )
+                {
+                    rc = -ERESTART;
+                    data->opaque = first_gfn;
+                    break;
+                }
+            }
+        }
+
         break;
     }
 
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 87f274d..03bc309 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 for a range of gfns from ot to nt. */
+void p2m_finish_type_change(struct domain *d,
+                            unsigned long first_gfn, unsigned long last_gfn,
+                            p2m_type_t ot, p2m_type_t nt)
+{
+    struct p2m_domain *p2m = p2m_get_hostp2m(d);
+    p2m_type_t t;
+    unsigned long gfn = first_gfn;
+
+    ASSERT(first_gfn <= last_gfn);
+    ASSERT(ot != nt);
+    ASSERT(p2m_is_changeable(ot) && p2m_is_changeable(nt));
+
+    p2m_lock(p2m);
+
+    last_gfn = min(last_gfn, p2m->max_mapped_pfn);
+    while ( gfn <= last_gfn )
+    {
+        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..3d665e8 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -611,6 +611,13 @@ 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 the p2m type for a range of gfns:
+ * [first_gfn ... last_gfn]. */
+void p2m_finish_type_change(struct domain *d,
+                            unsigned long first_gfn,
+                            unsigned long last_gfn,
+                            p2m_type_t ot, p2m_type_t nt);
+
 /* Report a change affecting memory types. */
 void p2m_memory_type_changed(struct domain *d);
 
-- 
1.9.1


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