Re: [Xen-devel] [PATCH v6 05/18] tools/libxc: support to resume uncooperative HVM guests

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Dec 30, 2015 at 10:28:55AM +0800, Wen Congyang wrote:
> Befor this patch:

s/Befor/Before
> 1. suspend
> a. PVHVM and PV: we use the same way to suspend the guest (send the suspend
>    request to the guest). If the guest doesn't support evtchn, the xenstore
>    variant will be used, suspending the guest via XenBus control node.
> b. pure HVM: we call xc_domain_shutdown(..., SHUTDOWN_suspend) to suspend
>    the guest
> 
> 2. Resume:
> a. fast path

s/fast path/fast path(fast=1)

>    In this case, we don't change the guest's state. And we will call
>    libxl__domain_resume(..., 1) to resume the guest.

Do not change the guest state. We call libxl__domain_resume(.., 1) which
calls xc_domain_resume(..., 1 /* fast=1*/) to resume the guest.


>    PV:       modify the return code to 1, and than call the domctl

s/domctl/domctl:/
>              XEN_DOMCTL_resumedomain
>    PVHVM:    same with PV
>    pure HVM: do nothing in modify_returncode, and than call the domctl:
>              XEN_DOMCTL_resumedomain

> b. slow
>    Used when the guest's state have been changed. And we will call

s/And we will/Will/

>    libxl__domain_resume(..., 0) to resume the guest.
>    PV:       update start info, and reset all secondary CPU states. Than call
>              the domctl: XEN_DOMCTL_resumedomain
>    PVHVM:    can not be resumed. You will get the following error message:
>                  "Cannot resume uncooperative HVM guests"
>    purt HVM: same with PVHVM
> 
> After this patch:
> 1. suspend
>    unchanged
> 
> 2. Resume
> a. fast path:
>    unchanged
> b. slow
>    PV:       unchanged
>    PVHVM:    call XEN_DOMCTL_resumedomain to resume the guest. Because we
>              don't modify the return code, the PV driver will disconnect
>              and reconnect. I am not sure if we should update start info
>              and reset all secondary CPU states.

The guest ends up doing the XENMAPSPACE_shared_info XENMEM_add_to_physmap
hypercall and resetting all of its CPU states to point to the shared_info
(well except the ones past 32).

That is the Linux kernel does that - regardless whether the 
SCHEDOP_shutdown:SHUTDOWN_suspend returns 1 or not.

>    Pure HVM: call XEN_DOMCTL_resumedomain to resume the guest.
> 
> Under COLO, we will update the guest's state(modify memory, cpu's registers,
> device status...). In this case, we cannot use the fast path to resume it.
> Keep the return code 0, and use a slow path to resume the guest. While
> resuming HVM using slow path is not supported currently, this patch is to
> make the resume call do not fail.

s/do/to/
> 
> Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
> Signed-off-by: Yang Hongyang <hongyang.yang@xxxxxxxxxxxx>
> ---
>  tools/libxc/xc_resume.c | 24 ++++++++++++++++++++----
>  1 file changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/libxc/xc_resume.c b/tools/libxc/xc_resume.c
> index 87d4324..503e4f8 100644
> --- a/tools/libxc/xc_resume.c
> +++ b/tools/libxc/xc_resume.c
> @@ -108,6 +108,25 @@ static int xc_domain_resume_cooperative(xc_interface 
> *xch, uint32_t domid)
>      return do_domctl(xch, &domctl);
>  }
>  
> +static int xc_domain_resume_hvm(xc_interface *xch, uint32_t domid)
> +{
> +    DECLARE_DOMCTL;
> +
> +    /*
> +     * This domctl XEN_DOMCTL_resumedomain just unpause each vcpu. After

s/This/The/
s/just//
> +     * this domctl, the guest will run.
s/this/the/

> +     *
> +     * If it is PVHVM, the guest called the hypercall HYPERVISOR_sched_op

s/HYPERVISOR_sched_op/SCHEDOP_shutdown:SHUTDOWN_suspend/
> +     * to suspend itself. We don't modify the return code, so the PV driver
> +     * will disconnect and reconnect.
> +     *
> +     * If it is a HVM, the guest will continue running.
> +     */
> +    domctl.cmd = XEN_DOMCTL_resumedomain;
> +    domctl.domain = domid;
> +    return do_domctl(xch, &domctl);
> +}
> +
>  static int xc_domain_resume_any(xc_interface *xch, uint32_t domid)
>  {
>      DECLARE_DOMCTL;
> @@ -137,10 +156,7 @@ static int xc_domain_resume_any(xc_interface *xch, 
> uint32_t domid)
>       */
>  #if defined(__i386__) || defined(__x86_64__)
>      if ( info.hvm )
> -    {
> -        ERROR("Cannot resume uncooperative HVM guests");
> -        return rc;
> -    }
> +        return xc_domain_resume_hvm(xch, domid);
>  
>      if ( xc_domain_get_guest_width(xch, domid, &dinfo->guest_width) != 0 )
>      {
> -- 
> 2.5.0
> 
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel

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