[Xen-changelog] [xen-4.1-testing] Fix shared entry status for grant copy operation on paged-out gfn

[Xen patchbot-4.1-testing <patchbot@xxxxxxx>]

# HG changeset patch
# User Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
# Date 1348131319 -7200
# Node ID 4210b36bfc416c27ed4d4313003a6278bdfdbb4a
# Parent  6162d01a51499009913119334fa6f061b5fea283
Fix shared entry status for grant copy operation on paged-out gfn

The unwind path was not clearing the shared entry status bits. This
was BSOD-ing guests on network activity under certain configurations.

Also:
 * sed the fixup method name to signal it's related to grant copy.
 * use atomic clear flag ops during fixup.

Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
xen-unstable changeset: 25771:1636cc4886f6
xen-unstable date: Wed Aug 22 21:27:50 UTC 2012
---


diff -r 6162d01a5149 -r 4210b36bfc41 xen/common/grant_table.c
--- a/xen/common/grant_table.c  Thu Sep 20 10:53:43 2012 +0200
+++ b/xen/common/grant_table.c  Thu Sep 20 10:55:19 2012 +0200
@@ -1707,14 +1707,14 @@ __release_grant_for_copy(
    under the domain's grant table lock. */
 /* Only safe on transitive grants.  Even then, note that we don't
    attempt to drop any pin on the referent grant. */
-static void __fixup_status_for_pin(const struct active_grant_entry *act,
+static void __fixup_status_for_copy_pin(const struct active_grant_entry *act,
                                    uint16_t *status)
 {
     if ( !(act->pin & GNTPIN_hstw_mask) )
-        *status &= ~GTF_writing;
+        gnttab_clear_flag(_GTF_writing, status);
 
     if ( !(act->pin & GNTPIN_hstr_mask) )
-        *status &= ~GTF_reading;
+        gnttab_clear_flag(_GTF_reading, status);
 }
 
 /* Grab a frame number from a grant entry and update the flags and pin
@@ -1794,7 +1794,7 @@ __acquire_grant_for_copy(
         if ( sha2 && (shah->flags & GTF_type_mask) == GTF_transitive )
         {
             if ( !allow_transitive )
-                PIN_FAIL(unlock_out, GNTST_general_error,
+                PIN_FAIL(unlock_out_clear, GNTST_general_error,
                          "transitive grant when transitivity not allowed\n");
 
             trans_domid = sha2->transitive.trans_domid;
@@ -1802,7 +1802,7 @@ __acquire_grant_for_copy(
             barrier(); /* Stop the compiler from re-loading
                           trans_domid from shared memory */
             if ( trans_domid == rd->domain_id )
-                PIN_FAIL(unlock_out, GNTST_general_error,
+                PIN_FAIL(unlock_out_clear, GNTST_general_error,
                          "transitive grants cannot be self-referential\n");
 
             /* We allow the trans_domid == ld->domain_id case, which
@@ -1814,7 +1814,7 @@ __acquire_grant_for_copy(
 
             rrd = rcu_lock_domain_by_id(trans_domid);
             if ( rrd == NULL )
-                PIN_FAIL(unlock_out, GNTST_general_error,
+                PIN_FAIL(unlock_out_clear, GNTST_general_error,
                          "transitive grant referenced bad domain %d\n",
                          trans_domid);
             spin_unlock(&rd->grant_table->lock);
@@ -1826,7 +1826,7 @@ __acquire_grant_for_copy(
 
             spin_lock(&rd->grant_table->lock);
             if ( rc != GNTST_okay ) {
-                __fixup_status_for_pin(act, status);
+                __fixup_status_for_copy_pin(act, status);
                 spin_unlock(&rd->grant_table->lock);
                 return rc;
             }
@@ -1837,7 +1837,7 @@ __acquire_grant_for_copy(
                and try again. */
             if ( act->pin != old_pin )
             {
-                __fixup_status_for_pin(act, status);
+                __fixup_status_for_copy_pin(act, status);
                 spin_unlock(&rd->grant_table->lock);
                 return __acquire_grant_for_copy(rd, gref, ld, readonly,
                                                 frame, page_off, length,
@@ -1857,7 +1857,7 @@ __acquire_grant_for_copy(
             gfn = sha1->frame;
             rc = __get_paged_frame(gfn, &grant_frame, readonly, rd);
             if ( rc != GNTST_okay )
-                goto unlock_out;
+                goto unlock_out_clear;
             act->gfn = gfn;
             is_sub_page = 0;
             trans_page_off = 0;
@@ -1869,7 +1869,7 @@ __acquire_grant_for_copy(
             gfn = sha2->full_page.frame;
             rc = __get_paged_frame(gfn, &grant_frame, readonly, rd);
             if ( rc != GNTST_okay )
-                goto unlock_out;
+                goto unlock_out_clear;
             act->gfn = gfn;
             is_sub_page = 0;
             trans_page_off = 0;
@@ -1881,7 +1881,7 @@ __acquire_grant_for_copy(
             gfn = sha2->sub_page.frame;
             rc = __get_paged_frame(gfn, &grant_frame, readonly, rd);
             if ( rc != GNTST_okay )
-                goto unlock_out;
+                goto unlock_out_clear;
             act->gfn = gfn;
             is_sub_page = 1;
             trans_page_off = sha2->sub_page.page_off;
@@ -1911,6 +1911,17 @@ __acquire_grant_for_copy(
     *length = act->length;
     *frame = act->frame;
 
+    spin_unlock(&rd->grant_table->lock);
+    return rc;
+
+ unlock_out_clear:
+    if ( !(readonly) &&
+         !(act->pin & GNTPIN_hstw_mask) )
+        gnttab_clear_flag(_GTF_writing, status);
+
+    if ( !act->pin )
+        gnttab_clear_flag(_GTF_reading, status);
+
  unlock_out:
     spin_unlock(&rd->grant_table->lock);
     return rc;

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