Re: [PATCH V3 2/3] xen/vm_event: Support for guest-requested events

[George Dunlap <george.dunlap@eu.citrix.com>]

On 07/06/2015 04:51 PM, Razvan Cojocaru wrote:
> Added support for a new class of vm_events: VM_EVENT_REASON_REQUEST,
> sent via HVMOP_request_vm_event. The guest can request that a
> generic vm_event (containing only the vm_event-filled guest registers
> as information) be sent to userspace by setting up the correct
> registers and doing a VMCALL. For example, for a 32-bit guest, this
> means: EAX = 34 (hvmop), EBX = 24 (HVMOP_guest_request_vm_event),
> ECX = 0 (NULL required for the hypercall parameter, reserved).
> 
> Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
> 
> ---
> Changes since V2:
>  - Renamed xc_monitor_requested() to xc_monitor_guest_request().
>  - Renamed 'requested' or 'request' to 'guest_request' (consistency).
>  - Removed the emoved #if defined(__XEN__) || defined(__XEN_TOOLS__)
>    restriction to defining HVMOP_guest_request_vm_event.
>  - Now requiring NULL as the hypercall parameter.
>  - Changed the type of struct monitor's bitfields from uint16_t to
>    unsigned int.
> ---
>  tools/libxc/include/xenctrl.h   |    2 ++
>  tools/libxc/xc_monitor.c        |   15 +++++++++++++++
>  xen/arch/x86/hvm/event.c        |   16 ++++++++++++++++
>  xen/arch/x86/hvm/hvm.c          |    8 +++++++-
>  xen/arch/x86/monitor.c          |   16 ++++++++++++++++
>  xen/include/asm-x86/domain.h    |   16 +++++++++-------
>  xen/include/asm-x86/hvm/event.h |    1 +
>  xen/include/public/domctl.h     |    6 ++++++
>  xen/include/public/hvm/hvm_op.h |    2 ++
>  xen/include/public/vm_event.h   |    2 ++
>  10 files changed, 76 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
> index d1d2ab3..4ce519a 100644
> --- a/tools/libxc/include/xenctrl.h
> +++ b/tools/libxc/include/xenctrl.h
> @@ -2384,6 +2384,8 @@ int xc_monitor_mov_to_msr(xc_interface *xch, domid_t domain_id, bool enable,
>  int xc_monitor_singlestep(xc_interface *xch, domid_t domain_id, bool enable);
>  int xc_monitor_software_breakpoint(xc_interface *xch, domid_t domain_id,
>                                     bool enable);
> +int xc_monitor_guest_request(xc_interface *xch, domid_t domain_id,
> +                             bool enable, bool sync);
>  
>  /***
>   * Memory sharing operations.
> diff --git a/tools/libxc/xc_monitor.c b/tools/libxc/xc_monitor.c
> index 63013de..d979122 100644
> --- a/tools/libxc/xc_monitor.c
> +++ b/tools/libxc/xc_monitor.c
> @@ -105,3 +105,18 @@ int xc_monitor_singlestep(xc_interface *xch, domid_t domain_id,
>  
>      return do_domctl(xch, &domctl);
>  }
> +
> +int xc_monitor_guest_request(xc_interface *xch, domid_t domain_id, bool enable,
> +                             bool sync)
> +{
> +    DECLARE_DOMCTL;
> +
> +    domctl.cmd = XEN_DOMCTL_monitor_op;
> +    domctl.domain = domain_id;
> +    domctl.u.monitor_op.op = enable ? XEN_DOMCTL_MONITOR_OP_ENABLE
> +                                    : XEN_DOMCTL_MONITOR_OP_DISABLE;
> +    domctl.u.monitor_op.event = XEN_DOMCTL_MONITOR_EVENT_GUEST_REQUEST;
> +    domctl.u.monitor_op.u.guest_request.sync = sync;
> +
> +    return do_domctl(xch, &domctl);
> +}
> diff --git a/xen/arch/x86/hvm/event.c b/xen/arch/x86/hvm/event.c
> index 5341937..17638ea 100644
> --- a/xen/arch/x86/hvm/event.c
> +++ b/xen/arch/x86/hvm/event.c
> @@ -126,6 +126,22 @@ void hvm_event_msr(unsigned int msr, uint64_t value)
>          hvm_event_traps(1, &req);
>  }
>  
> +void hvm_event_guest_request(void)
> +{
> +    struct vcpu *curr = current;
> +    struct arch_domain *currad = &curr->domain->arch;
> +
> +    if ( currad->monitor.guest_request_enabled )
> +    {
> +        vm_event_request_t req = {
> +            .reason = VM_EVENT_REASON_GUEST_REQUEST,
> +            .vcpu_id = curr->vcpu_id,
> +        };
> +
> +        hvm_event_traps(currad->monitor.guest_request_sync, &req);
> +    }
> +}
> +
>  int hvm_event_int3(unsigned long gla)
>  {
>      int rc = 0;
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index 535d622..536d1c8 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -5974,7 +5974,6 @@ static int hvmop_get_param(
>  #define HVMOP_op_mask 0xff
>  
>  long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE_PARAM(void) arg)
> -
>  {
>      unsigned long start_iter, mask;
>      long rc = 0;
> @@ -6388,6 +6387,13 @@ long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE_PARAM(void) arg)
>          break;
>      }
>  
> +    case HVMOP_guest_request_vm_event:
> +        if ( guest_handle_is_null(arg) )
> +            hvm_event_guest_request();
> +        else
> +            rc = -EINVAL;
> +        break;
> +
>      default:
>      {
>          gdprintk(XENLOG_DEBUG, "Bad HVM op %ld.\n", op);
> diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
> index 896acf7..f8df7d2 100644
> --- a/xen/arch/x86/monitor.c
> +++ b/xen/arch/x86/monitor.c
> @@ -161,6 +161,22 @@ int monitor_domctl(struct domain *d, struct xen_domctl_monitor_op *mop)
>          break;
>      }
>  
> +    case XEN_DOMCTL_MONITOR_EVENT_GUEST_REQUEST:
> +    {
> +        bool_t status = ad->monitor.guest_request_enabled;
> +
> +        rc = status_check(mop, status);
> +        if ( rc )
> +            return rc;
> +
> +        ad->monitor.guest_request_sync = mop->u.guest_request.sync;
> +
> +        domain_pause(d);
> +        ad->monitor.guest_request_enabled = !status;

If I'm reading this right, what this hypercall does is *toggle* guest
requests?

Wouldn't it make more sense to either set it or clear it, rather than
have the caller need to keep track (or guess) what state it's in?

 -George