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Re: [Xen-devel] [PATCH V5] x86/ioreq_server: Make p2m_finish_type_change actually work

Hi, On 15/05/17 14:47, George Dunlap wrote:

On Sat, May 13, 2017 at 1:34 AM, Xiong Zhang <xiong.y.zhang@xxxxxxxxx> wrote:

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>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
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)
v5: Fix coding style. (Julien)

The target of this patch is Xen 4.9.
---
 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 |  9 +++++----
 5 files changed, 33 insertions(+), 18 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..1600422 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.
+         */


Hmm, now that these functions are being called externally it would be
good if their semantics was the same.  But since we're a bit late in
the cycle to do that kind of rework:

I guess this is a call for a rework after the tree has opened?


Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>

Release-acked-by: Julien Grall <julien.grall@xxxxxxx> Cheers, -- Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel

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