Re: [Xen-devel] [PATCH] xen: fix initialization of wallclock time for PVHVM on migration

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.06.13 at 12:46, Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
> The initial values of the wallclock time in the shared info page are
> set for PVHVM guests when the hypercall page is initialized, since the
> hypercall page is not reinitialized on resume, the hypervisor
> wallclock time is not properly set on resume.
> 
> Fix it by forcing an update of the wallclock values when the shared
> info page is mapped.

NACK - this is a guest side bug. After migration, a guest _has_ to
re-init the hypercall page, as it may have got migrated between
a VMX and an SVM machine, and the hypercall instructions are
different between them.

Jan

> Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
> Cc: Jan Beulich <JBeulich@xxxxxxxx>
> Cc: Keir Fraser <keir@xxxxxxx>
> Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> ---
> Since this is a bug fix, I think it is suitable for inclusion in the
> 4.3 release, and backported to older releases.
> ---
>  xen/arch/x86/mm.c |    8 ++++++++
>  1 files changed, 8 insertions(+), 0 deletions(-)
> 
> diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
> index 5123860..1591528 100644
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -4629,6 +4629,14 @@ static int xenmem_add_to_physmap_once(
>          put_gfn(d, gfn);
>      domain_unlock(d);
>  
> +    if ( !rc && xatp->space == XENMAPSPACE_shared_info )
> +        /*
> +         * Force an update of the wallclock values in the shared info
> +         * page, since in the PVHVM resume path the hypercall page is
> +         * not reinitialized.
> +         */
> +        update_domain_wallclock_time(d);
> +
>      return rc;
>  }
>  
> -- 
> 1.7.7.5 (Apple Git-26)



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