Re: [Xen-devel] [PATCH V3] x86/monitor: Disallow setting mem_access_emulate_each_rep when vm_event is NULL

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.04.16 at 18:12, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> On 04/09/16 08:54, Razvan Cojocaru wrote:
>> 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>
>> 
>> ---
>> 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,
> 
> According to the previous list discussion with Andrew Cooper, this fix
> might be considered for the 4.7 release, so CC-ing Wei for a release
> ack, as suggested.

Even if - without the pending ./MAINTAINERS adjustment - not
formally required, I don't understand why you didn't Cc Tamas on
this patch. I don't think this should go in without his ack.

Jan


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