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

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

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.

>
> Please try the following hypervisor patch instead:
>
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index 3a09439..9ee56b3 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -5748,12 +5748,13 @@ long do_hvm_op(unsigned long op,
> XEN_GUEST_HANDLE_PARAM(void) arg)
>                   if ( curr_d == d )
>                       break;
>
> -                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;
>
>                   /*
> @@ -5767,7 +5768,6 @@ long do_hvm_op(unsigned long op,
> XEN_GUEST_HANDLE_PARAM(void) arg)
>
>                   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.