Re: [Xen-devel] [PATCH v3 1/3] introduce GFN notification for translated domains

[Jan Beulich <jbeulich@xxxxxxxx>]

On 25.11.2019 11:37,  Durrant, Paul  wrote:
>> -----Original Message-----
>> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of Jan
>> Beulich
>> Sent: 25 November 2019 09:58
>>
>> --- a/xen/arch/x86/hvm/hvm.c
>> +++ b/xen/arch/x86/hvm/hvm.c
>> @@ -4304,9 +4304,17 @@ static int hvmop_set_param(
>>          if ( a.value > SHUTDOWN_MAX )
>>              rc = -EINVAL;
>>          break;
>> +
>>      case HVM_PARAM_IOREQ_SERVER_PFN:
>> -        d->arch.hvm.ioreq_gfn.base = a.value;
>> +        if ( d->arch.hvm.params[HVM_PARAM_NR_IOREQ_SERVER_PAGES] )
>> +            rc = notify_gfn(
>> +                     d,
>> +                     _gfn(a.value + d->arch.hvm.params
>> +                                    [HVM_PARAM_NR_IOREQ_SERVER_PAGES] -
>> 1));
> 
> IIRC the PFN is typically set by the toolstack before the number of
> pages, so the notify will be for a.value - 1, i.e. the previous gfn.
> Is that a problem?

There's an if() around the invocation to avoid this situation, so I'm
afraid I don't understand the question.

Jan

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