[v10,33/59] hw/xen: Implement EVTCHNOP_bind_ipi

From: David Woodhouse <dwmw@amazon.co.uk>

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 hw/i386/kvm/xen_evtchn.c  | 69 +++++++++++++++++++++++++++++++++++++++
 hw/i386/kvm/xen_evtchn.h  |  2 ++
 target/i386/kvm/xen-emu.c | 15 +++++++++
 3 files changed, 86 insertions(+)

On 01/02/2023 14:31, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
>   hw/i386/kvm/xen_evtchn.c  | 69 +++++++++++++++++++++++++++++++++++++++
>   hw/i386/kvm/xen_evtchn.h  |  2 ++
>   target/i386/kvm/xen-emu.c | 15 +++++++++
>   3 files changed, 86 insertions(+)
> 
> diff --git a/hw/i386/kvm/xen_evtchn.c b/hw/i386/kvm/xen_evtchn.c
> index da2f5711dd..d8527483b9 100644
> --- a/hw/i386/kvm/xen_evtchn.c
> +++ b/hw/i386/kvm/xen_evtchn.c
> @@ -13,6 +13,7 @@
>   #include "qemu/host-utils.h"
>   #include "qemu/module.h"
>   #include "qemu/main-loop.h"
> +#include "qemu/log.h"
>   #include "qapi/error.h"
>   #include "qom/object.h"
>   #include "exec/target_page.h"
> @@ -231,6 +232,43 @@ static void inject_callback(XenEvtchnState *s, uint32_t vcpu)
>       kvm_xen_inject_vcpu_callback_vector(vcpu, type);
>   }
>   
> +static void deassign_kernel_port(evtchn_port_t port)
> +{
> +    struct kvm_xen_hvm_attr ha;
> +    int ret;
> +
> +    ha.type = KVM_XEN_ATTR_TYPE_EVTCHN;
> +    ha.u.evtchn.send_port = port;
> +    ha.u.evtchn.flags = KVM_XEN_EVTCHN_DEASSIGN;
> +
> +    ret = kvm_vm_ioctl(kvm_state, KVM_XEN_HVM_SET_ATTR, &ha);
> +    if (ret) {
> +        qemu_log_mask(LOG_GUEST_ERROR, "Failed to unbind kernel port %d: %s\n",
> +                      port, strerror(ret));
> +    }
> +}
> +
> +static int assign_kernel_port(uint16_t type, evtchn_port_t port,
> +                              uint32_t vcpu_id)
> +{
> +    CPUState *cpu = qemu_get_cpu(vcpu_id);
> +    struct kvm_xen_hvm_attr ha;
> +
> +    if (!cpu) {
> +        return -ENOENT;
> +    }
> +
> +    ha.type = KVM_XEN_ATTR_TYPE_EVTCHN;
> +    ha.u.evtchn.send_port = port;
> +    ha.u.evtchn.type = type;
> +    ha.u.evtchn.flags = 0;
> +    ha.u.evtchn.deliver.port.port = port;
> +    ha.u.evtchn.deliver.port.vcpu = kvm_arch_vcpu_id(cpu);
> +    ha.u.evtchn.deliver.port.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
> +
> +    return kvm_vm_ioctl(kvm_state, KVM_XEN_HVM_SET_ATTR, &ha);
> +}
> +
>   static bool valid_port(evtchn_port_t port)
>   {
>       if (!port) {
> @@ -549,6 +587,12 @@ static int close_port(XenEvtchnState *s, evtchn_port_t port)
>                                 p->type_val, 0);
>           break;
>   
> +    case EVTCHNSTAT_ipi:
> +        if (s->evtchn_in_kernel) {
> +            deassign_kernel_port(port);
> +        }
> +        break;
> +
>       default:
>           break;
>       }
> @@ -638,3 +682,28 @@ int xen_evtchn_bind_virq_op(struct evtchn_bind_virq *virq)
>   
>       return ret;
>   }
> +
> +int xen_evtchn_bind_ipi_op(struct evtchn_bind_ipi *ipi)
> +{
> +    XenEvtchnState *s = xen_evtchn_singleton;
> +    int ret;
> +
> +    if (!s) {
> +        return -ENOTSUP;
> +    }
> +
> +    if (!valid_vcpu(ipi->vcpu)) {
> +        return -ENOENT;
> +    }
> +
> +    qemu_mutex_lock(&s->port_lock);
> +
> +    ret = allocate_port(s, ipi->vcpu, EVTCHNSTAT_ipi, 0, &ipi->port);
> +    if (!ret && s->evtchn_in_kernel) {
> +        assign_kernel_port(EVTCHNSTAT_ipi, ipi->port, ipi->vcpu);

Should the error not be propagated here?

   Paul

> +    }
> +
> +    qemu_mutex_unlock(&s->port_lock);
> +
> +    return ret;
> +}
> diff --git a/hw/i386/kvm/xen_evtchn.h b/hw/i386/kvm/xen_evtchn.h
> index 0ea13dda3a..107f420848 100644
> --- a/hw/i386/kvm/xen_evtchn.h
> +++ b/hw/i386/kvm/xen_evtchn.h
> @@ -19,9 +19,11 @@ struct evtchn_status;
>   struct evtchn_close;
>   struct evtchn_unmask;
>   struct evtchn_bind_virq;
> +struct evtchn_bind_ipi;
>   int xen_evtchn_status_op(struct evtchn_status *status);
>   int xen_evtchn_close_op(struct evtchn_close *close);
>   int xen_evtchn_unmask_op(struct evtchn_unmask *unmask);
>   int xen_evtchn_bind_virq_op(struct evtchn_bind_virq *virq);
> +int xen_evtchn_bind_ipi_op(struct evtchn_bind_ipi *ipi);
>   
>   #endif /* QEMU_XEN_EVTCHN_H */
> diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
> index 0c4988ad63..4a20ccdf78 100644
> --- a/target/i386/kvm/xen-emu.c
> +++ b/target/i386/kvm/xen-emu.c
> @@ -891,6 +891,21 @@ static bool kvm_xen_hcall_evtchn_op(struct kvm_xen_exit *exit, X86CPU *cpu,
>           }
>           break;
>       }
> +    case EVTCHNOP_bind_ipi: {
> +        struct evtchn_bind_ipi ipi;
> +
> +        qemu_build_assert(sizeof(ipi) == 8);
> +        if (kvm_copy_from_gva(cs, arg, &ipi, sizeof(ipi))) {
> +            err = -EFAULT;
> +            break;
> +        }
> +
> +        err = xen_evtchn_bind_ipi_op(&ipi);
> +        if (!err && kvm_copy_to_gva(cs, arg, &ipi, sizeof(ipi))) {
> +            err = -EFAULT;
> +        }
> +        break;
> +    }
>       default:
>           return false;
>       }

On Fri, 2023-02-10 at 13:55 +0000, Paul Durrant wrote:
> 
> > +    ret = allocate_port(s, ipi->vcpu, EVTCHNSTAT_ipi, 0, &ipi->port);
> > +    if (!ret && s->evtchn_in_kernel) {
> > +        assign_kernel_port(EVTCHNSTAT_ipi, ipi->port, ipi->vcpu);
> 
> Should the error not be propagated here?


Nah, we'll just fall back to doing it in userspace.

The kernel acceleration is nice to have (and I mean *really* nice to
have, for IPIs), but it works without.

On 10/02/2023 14:15, David Woodhouse wrote:
> On Fri, 2023-02-10 at 13:55 +0000, Paul Durrant wrote:
>>
>>> +    ret = allocate_port(s, ipi->vcpu, EVTCHNSTAT_ipi, 0, &ipi->port);
>>> +    if (!ret && s->evtchn_in_kernel) {
>>> +        assign_kernel_port(EVTCHNSTAT_ipi, ipi->port, ipi->vcpu);
>>
>> Should the error not be propagated here?
> 
> 
> Nah, we'll just fall back to doing it in userspace.
> 
> The kernel acceleration is nice to have (and I mean *really* nice to
> have, for IPIs), but it works without.

Ok.

Reviewed-by: Paul Durrant <paul@xen.org>