[Xen-changelog] [xen master] x86/monitor: disallow setting mem_access_emulate_each_rep when vm_event is NULL

[patchbot@xxxxxxx]

commit fdfd56453db7c303c8c82531b33401f40700a85e
Author:     Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
AuthorDate: Wed May 4 09:42:06 2016 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed May 4 09:42:06 2016 +0200

    x86/monitor: disallow setting mem_access_emulate_each_rep when vm_event is 
NULL
    
    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@xxxxxxxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    Acked-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
---
 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,
--
generated by git-patchbot for /home/xen/git/xen.git#master

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