Re: [Xen-devel] [PATCH] x86/hvm: don't create a default ioreq server...

[Zhang Chen <zhangchen.fnst@xxxxxxxxxxxxxx>]

On 12/10/2016 02:21 AM, Andrew Cooper wrote:
> On 09/12/16 17:55, Paul Durrant wrote:
> > ...if the domain is not under construction.
> >
> > If upstream QEMU is in use then it will explicitly create an ioreq server
> > rather than implicitly creating the default ioreq server, which is a
> > side-effect of reading HVM_PARAM_IOREQ_PFN, HVM_PARAM_BUFIOREQ_PFN,
> > or HVM_PARAM_BUFIOREQ_EVTCHN (as is done by legacy QEMUs).
> >
> > However, if the domain is subsequently saved/migrated then those parameters
> > are read and hence the default server will be unnecessarily instantiated.
> >
> > This patch adds an extra check of the 'creation_finished' flag when those
> > HVM params are read and will only instantiate the server if the domain is
> > under construction, which will always be the case when QEMU is invoked.
> >
> > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>
> CC'ing the COLO guys.  Please can you test with this patch?
Tested-by: Zhang Chen <zhangchen.fnst@xxxxxxxxxxxxxx>

I have tested this patch, it works well on COLO!

Thanks
Zhang Chen


> > ---
> > Cc: Jan Beulich <jbeulich@xxxxxxxx>
> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > ---
> >   xen/arch/x86/hvm/hvm.c | 11 ++++++++++-
> >   1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> > index e0f936b..c531f37 100644
> > --- a/xen/arch/x86/hvm/hvm.c
> > +++ b/xen/arch/x86/hvm/hvm.c
> > @@ -5337,7 +5337,16 @@ static int hvmop_get_param(
> >       {
> >           domid_t domid;
> >   
> > -        /* May need to create server. */
> > +        /*
> > +         * It may be necessary to create a default ioreq server here,
> > +         * because legacy versions of QEMU are not aware of the new API
> > +         * for explicit ioreq server creation. However, if the domain
> > +         * is not under construction then it will not be QEMU querying
> > +         * the parameters and thus the query should have that side-effect.
> > +         */
> > +        if ( d->creation_finished )
> > +            break;
> > +
> >           domid = d->arch.hvm_domain.params[HVM_PARAM_DM_DOMAIN];
> >           rc = hvm_create_ioreq_server(d, domid, 1,
> >                                        HVM_IOREQSRV_BUFIOREQ_LEGACY, NULL);
>
> .
--
Thanks
zhangchen




_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel