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* [PATCH V3] x86/monitor: Disallow setting mem_access_emulate_each_rep when vm_event is NULL
@ 2016-04-09  5:54 Razvan Cojocaru
  2016-04-29 16:12 ` Razvan Cojocaru
  0 siblings, 1 reply; 6+ messages in thread
From: Razvan Cojocaru @ 2016-04-09  5:54 UTC (permalink / raw)
  To: xen-devel; +Cc: andrew.cooper3, keir, Razvan Cojocaru, jbeulich

It is meaningless (and potentially dangerous - see hvmemul_virtual_to_linear())
to set mem_access_emulate_each_rep before xc_monitor_enable() (which allocates
vcpu->arch.vm_event) has been called, so return an error from the
XEN_DOMCTL_MONITOR_OP_EMULATE_EACH_REP hypercall when that is the case.

Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citirx.com>

---
Changes since V2:
 - Updated the if() condition as recommended by Andrew Cooper.
 - Added Andrew Cooper's Reviewed-by.
---
 xen/include/asm-x86/monitor.h | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
index 0954b59..d367099 100644
--- a/xen/include/asm-x86/monitor.h
+++ b/xen/include/asm-x86/monitor.h
@@ -32,19 +32,29 @@
 static inline
 int arch_monitor_domctl_op(struct domain *d, struct xen_domctl_monitor_op *mop)
 {
+    int rc = 0;
+
     switch ( mop->op )
     {
     case XEN_DOMCTL_MONITOR_OP_EMULATE_EACH_REP:
         domain_pause(d);
-        d->arch.mem_access_emulate_each_rep = !!mop->event;
+        /*
+         * Enabling mem_access_emulate_each_rep without a vm_event subscriber
+         * is meaningless.
+         */
+        if ( d->max_vcpus && d->vcpu[0] && d->vcpu[0]->arch.vm_event )
+            d->arch.mem_access_emulate_each_rep = !!mop->event;
+        else
+            rc = -EINVAL;
+
         domain_unpause(d);
         break;
 
     default:
-        return -EOPNOTSUPP;
+        rc = -EOPNOTSUPP;
     }
 
-    return 0;
+    return rc;
 }
 
 int arch_monitor_domctl_event(struct domain *d,
-- 
1.9.1


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^ permalink raw reply related	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2016-05-03 18:28 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-04-09  5:54 [PATCH V3] x86/monitor: Disallow setting mem_access_emulate_each_rep when vm_event is NULL Razvan Cojocaru
2016-04-29 16:12 ` Razvan Cojocaru
2016-05-02 10:26   ` Wei Liu
2016-05-03  8:14   ` Jan Beulich
2016-05-03  8:18     ` Razvan Cojocaru
2016-05-03 18:28       ` Tamas K Lengyel

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