Re: [PATCH Remus v1 5/8] tools/libxc: defer the setting of HVM_PARAM_IDENT_PT

[Hongyang Yang <yanghy@cn.fujitsu.com>]

Hi Andrew,

On 05/07/2015 11:24 PM, Andrew Cooper wrote:
> On 07/05/15 14:59, Hongyang Yang wrote:
>>
>>
>> On 05/07/2015 06:35 PM, Andrew Cooper wrote:
>>> On 07/05/15 07:37, Yang Hongyang wrote:
>>>> Set the hvm param HVM_PARAM_IDENT_PT second time will fail.
>>>> So defer the setting of HVM_PARAM_IDENT_PT.
>>>>
>>>> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
>>>
>>> I would argue that this is a Xen bug, not a migration bug.  There is
>>> nothing conceptually wrong with setting this param multiple times.
>>
>> I noticed that in legacy migration, this was set multiple times, so
>> this patch is only a workaround that will avoid the fail in my test.
>> will try your hypervisor patch tomorrow.
>
> Try this version, which has been rebased over Pauls' cleanup in this
> area which has just been committed to staging.

A quick test show that this patch fix the problem, will you send this
patch separately or I put this patch into my series?

>
> ~Andrew
>
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index 371fd33..941e9ea 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -5710,12 +5710,13 @@ static int hvmop_set_param(
>               rc = -EINVAL;
>           break;
>       case HVM_PARAM_IDENT_PT:
> -        rc = -EINVAL;
> -        if ( d->arch.hvm_domain.params[a.index] != 0 )
> -            break;
> -
>           rc = 0;
> -        if ( !paging_mode_hap(d) )
> +        d->arch.hvm_domain.params[a.index] = a.value;
> +        /*
> +         * Only actually required for VT-x lacking unrestricted_guest
> +         * capabilities.  Short circuit the pause if possible.
> +         */
> +        if ( !paging_mode_hap(d) || !cpu_has_vmx )
>               break;
>
>           /*
> @@ -5729,7 +5730,6 @@ static int hvmop_set_param(
>
>           rc = 0;
>           domain_pause(d);
> -        d->arch.hvm_domain.params[a.index] = a.value;
>           for_each_vcpu ( d, v )
>               paging_update_cr3(v);
>           domain_unpause(d);
>
> .
>

-- 
Thanks,
Yang.