[Xen-devel] [PATCH V4] x86/ioreq_server: Make p2m_finish_type_change actually work

[Xiong Zhang <xiong.y.zhang@xxxxxxxxx>]

Commit 6d774a951696 ("x86/ioreq server: synchronously reset outstanding
p2m_ioreq_server entries when an ioreq server unmaps") introduced
p2m_finish_type_change(), which was meant to synchronously finish a
previously initiated type change over a gpfn range.  It did this by
calling get_entry(), checking if it was the appropriate type, and then
calling set_entry().

Unfortunately, a previous commit (1679e0df3df6 "x86/ioreq server:
asynchronously reset outstanding p2m_ioreq_server entries") modified
get_entry() to always return the new type after the type change, meaning
that p2m_finish_type_change() never changed any entries.  Which means
when an ioreq server was detached and then re-attached (as happens in
XenGT on reboot) the re-attach failed.

Fix this by using the existing p2m-specific recalculation logic instead
of doing a read-check-write loop.

Fix: 'commit 6d774a951696 ("x86/ioreq server: synchronously reset
      outstanding p2m_ioreq_server entries when an ioreq server unmaps")'

Signed-off-by: Xiong Zhang <xiong.y.zhang@xxxxxxxxx>
Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxx>
---
v1: Add ioreq_pre_recalc query flag to get the old p2m_type.(Jan)
v2: Add p2m->recalc() hook to change gfn p2m_type. (George)
v3: Make commit message clearer. (George)
    Keep the name of p2m-specific recal function unchanged. (Jan)
v4: Move version info below S-o-B and handle return value of
    p2m->recalc. (Jan)
---
 xen/arch/x86/hvm/dm.c     |  5 +++--
 xen/arch/x86/mm/p2m-ept.c |  1 +
 xen/arch/x86/mm/p2m-pt.c  |  1 +
 xen/arch/x86/mm/p2m.c     | 35 +++++++++++++++++++++++------------
 xen/include/asm-x86/p2m.h |  7 ++++---
 5 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/xen/arch/x86/hvm/dm.c b/xen/arch/x86/hvm/dm.c
index d72b7bd..99bf66a 100644
--- a/xen/arch/x86/hvm/dm.c
+++ b/xen/arch/x86/hvm/dm.c
@@ -412,8 +412,9 @@ static int dm_op(domid_t domid,
                     first_gfn <= p2m->max_mapped_pfn )
             {
                 /* Iterate p2m table for 256 gfns each time. */
-                p2m_finish_type_change(d, _gfn(first_gfn), 256,
-                                       p2m_ioreq_server, p2m_ram_rw);
+                rc = p2m_finish_type_change(d, _gfn(first_gfn), 256);
+                if ( rc < 0 )
+                    break;
 
                 first_gfn += 256;
 
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index f37a1f2..09efba7 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -1238,6 +1238,7 @@ int ept_p2m_init(struct p2m_domain *p2m)
 
     p2m->set_entry = ept_set_entry;
     p2m->get_entry = ept_get_entry;
+    p2m->recalc = resolve_misconfig;
     p2m->change_entry_type_global = ept_change_entry_type_global;
     p2m->change_entry_type_range = ept_change_entry_type_range;
     p2m->memory_type_changed = ept_memory_type_changed;
diff --git a/xen/arch/x86/mm/p2m-pt.c b/xen/arch/x86/mm/p2m-pt.c
index 5079b59..2eddeee 100644
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -1153,6 +1153,7 @@ void p2m_pt_init(struct p2m_domain *p2m)
 {
     p2m->set_entry = p2m_pt_set_entry;
     p2m->get_entry = p2m_pt_get_entry;
+    p2m->recalc = do_recalc;
     p2m->change_entry_type_global = p2m_pt_change_entry_type_global;
     p2m->change_entry_type_range = p2m_pt_change_entry_type_range;
     p2m->write_p2m_entry = paging_write_p2m_entry;
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 1d57e5c..668c5a6 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1011,33 +1011,44 @@ 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,
-                            gfn_t first_gfn, unsigned long max_nr,
-                            p2m_type_t ot, p2m_type_t nt)
+/*
+ * Finish p2m type change for gfns which are marked as need_recalc in a range.
+ * Returns: 0/1 for success, negative for failure
+ */
+int p2m_finish_type_change(struct domain *d,
+                           gfn_t first_gfn, unsigned long max_nr)
 {
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
-    p2m_type_t t;
     unsigned long gfn = gfn_x(first_gfn);
     unsigned long last_gfn = gfn + max_nr - 1;
-
-    ASSERT(ot != nt);
-    ASSERT(p2m_is_changeable(ot) && p2m_is_changeable(nt));
+    int rc = 0;
 
     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);
+        rc = p2m->recalc(p2m, gfn);
+        /* 
+         * ept->recalc could return 0/1/-ENOMEM. pt->recalc could return
+         * 0/-ENOMEM/-ENOENT, -ENOENT isn't an error as we are looping
+         * gfn here.
+         */
+        if ( rc == -ENOENT)
+            rc = 0;
+        else if ( rc < 0 )
+        {
+            gdprintk(XENLOG_ERR, "p2m->recalc failed! Dom%d gfn=%lx\n",
+                     d->domain_id, gfn);
+            break;
+        }
 
         gfn++;
     }
 
     p2m_unlock(p2m);
+
+    return rc;
 }
 
 /*
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 7574a9b..d7d47fe 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -246,6 +246,8 @@ struct p2m_domain {
                                     p2m_query_t q,
                                     unsigned int *page_order,
                                     bool_t *sve);
+    int                (*recalc)(struct p2m_domain *p2m,
+                                 unsigned long gfn);
     void               (*enable_hardware_log_dirty)(struct p2m_domain *p2m);
     void               (*disable_hardware_log_dirty)(struct p2m_domain *p2m);
     void               (*flush_hardware_cached_dirty)(struct p2m_domain *p2m);
@@ -607,10 +609,9 @@ 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 */
-void p2m_finish_type_change(struct domain *d,
+int p2m_finish_type_change(struct domain *d,
                             gfn_t first_gfn,
-                            unsigned long max_nr,
-                            p2m_type_t ot, p2m_type_t nt);
+                            unsigned long max_nr);
 
 /* Report a change affecting memory types. */
 void p2m_memory_type_changed(struct domain *d);
-- 
2.7.4


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