Re: [Xen-devel] [PATCH v5] x86/hvm: Add per-vcpu evtchn upcalls

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Andrew Cooper
> Sent: 16 January 2015 10:39
> To: Paul Durrant; xen-devel@xxxxxxxxxxxxx
> Cc: Keir (Xen.org); David Vrabel; Jan Beulich
> Subject: Re: [Xen-devel] [PATCH v5] x86/hvm: Add per-vcpu evtchn upcalls
> 
> On 16/01/15 10:09, Paul Durrant wrote:
> > HVM guests have always been confined to using the domain callback
> > via (see HVM_PARAM_CALLBACK_IRQ) to receive event notifications.
> > This is usually an IOAPIC vector and is only used if the event
> > channel is bound to vcpu 0.
> >
> > PVHVM Linux uses a pre-defined interrupt vector for the event
> > channel upcall, set using HVM_PARAM_CALLBACK_IRQ by ORing in a
> > special bit (bit 57) into the value (see params.h). However, it
> > does not assert the interrupt via the emulated local APIC.
> >
> > This mechanism is not suitable in the general case since Windows
> > (and potentially other OSes) because they:
> >
> > - cannot guarantee the same vector for all VCPUs
> > - do require the upcall to be asserted via the local APIC
> >
> > This patch adds a new HVM op allowing a guest to specify a local
> > APIC vector to use as an upcall notification for a specific vcpu
> > therefore coping with the case of differing vector numbers.
> >
> > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> > Cc: Keir Fraser <keir@xxxxxxx>
> > Cc: Jan Beulich <jbeulich@xxxxxxxx>
> > Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
> > ---
> > v2:
> >  - Addressed comments from Andrew Cooper
> >    - Check vector >=16
> >    - Put hypercall in x86-specific section
> >
> > v3:
> >  - Addressed comments from Jan Beulich
> >    - More verbose check-in comment
> >
> > v4:
> >  - Amended check-in comment as suggested by David Vrabel
> >
> > v5:
> >  - Addressed comments from Jan Beulich
> >
> >  xen/arch/x86/hvm/hvm.c          |   30
> ++++++++++++++++++++++++++++++
> >  xen/arch/x86/hvm/irq.c          |    8 +++++++-
> >  xen/include/asm-x86/hvm/vcpu.h  |    1 +
> >  xen/include/public/hvm/hvm_op.h |   19 +++++++++++++++++++
> >  4 files changed, 57 insertions(+), 1 deletion(-)
> >
> > diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> > index 8b06bfd..85e43b8 100644
> > --- a/xen/arch/x86/hvm/hvm.c
> > +++ b/xen/arch/x86/hvm/hvm.c
> > @@ -5514,6 +5514,31 @@ static int hvmop_destroy_ioreq_server(
> >      return rc;
> >  }
> >
> > +static int hvmop_set_evtchn_upcall_vector(
> > +    XEN_GUEST_HANDLE_PARAM(xen_hvm_set_evtchn_upcall_vector_t)
> uop)
> > +{
> > +    xen_hvm_set_evtchn_upcall_vector_t op;
> > +    struct domain *d = current->domain;
> > +    struct vcpu *v;
> > +
> > +    if ( copy_from_guest(&op, uop, 1) )
> > +        return -EFAULT;
> > +
> > +    if ( !is_hvm_domain(d) )
> > +        return -EINVAL;
> > +
> > +    if ( op.vector < 0x10 )
> > +        return -EINVAL;
> > +
> > +    if ( op.vcpu >= d->max_vcpus || (v = d->vcpu[op.vcpu]) == NULL )
> > +        return -ENOENT;
> > +
> > +    printk(XENLOG_G_INFO "%pv: upcall vector %u\n", v, op.vector);
> > +
> > +    v->arch.hvm_vcpu.evtchn_upcall_vector = op.vector;
> > +    return 0;
> > +}
> > +
> >  /*
> >   * Note that this value is effectively part of the ABI, even if we don't 
> > need
> >   * to make it a formal part of it: A guest suspended for migration in the
> > @@ -5573,6 +5598,11 @@ long do_hvm_op(unsigned long op,
> XEN_GUEST_HANDLE_PARAM(void) arg)
> >              guest_handle_cast(arg, xen_hvm_destroy_ioreq_server_t));
> >          break;
> >
> > +    case HVMOP_set_evtchn_upcall_vector:
> > +        rc = hvmop_set_evtchn_upcall_vector(
> > +            guest_handle_cast(arg, xen_hvm_set_evtchn_upcall_vector_t));
> > +        break;
> > +
> >      case HVMOP_set_param:
> >      case HVMOP_get_param:
> >      {
> > diff --git a/xen/arch/x86/hvm/irq.c b/xen/arch/x86/hvm/irq.c
> > index 35f4f94..743429e 100644
> > --- a/xen/arch/x86/hvm/irq.c
> > +++ b/xen/arch/x86/hvm/irq.c
> > @@ -218,7 +218,13 @@ void hvm_assert_evtchn_irq(struct vcpu *v)
> >          return;
> >      }
> >
> > -    if ( is_hvm_pv_evtchn_vcpu(v) )
> > +    if ( v->arch.hvm_vcpu.evtchn_upcall_vector != 0 )
> > +    {
> > +        uint8_t vector = v->arch.hvm_vcpu.evtchn_upcall_vector;
> > +
> > +        vlapic_set_irq(vcpu_vlapic(v), vector, 0);
> > +    }
> > +    else if ( is_hvm_pv_evtchn_vcpu(v) )
> >          vcpu_kick(v);
> >      else if ( v->vcpu_id == 0 )
> >          hvm_set_callback_irq_level(v);
> > diff --git a/xen/include/asm-x86/hvm/vcpu.h b/xen/include/asm-
> x86/hvm/vcpu.h
> > index 01e0665..edd4523 100644
> > --- a/xen/include/asm-x86/hvm/vcpu.h
> > +++ b/xen/include/asm-x86/hvm/vcpu.h
> > @@ -160,6 +160,7 @@ struct hvm_vcpu {
> >      } u;
> >
> >      struct tasklet      assert_evtchn_irq_tasklet;
> > +    u8                  evtchn_upcall_vector;
> >
> >      struct nestedvcpu   nvcpu;
> >
> > diff --git a/xen/include/public/hvm/hvm_op.h
> b/xen/include/public/hvm/hvm_op.h
> > index a4e5345..a857561 100644
> > --- a/xen/include/public/hvm/hvm_op.h
> > +++ b/xen/include/public/hvm/hvm_op.h
> > @@ -370,6 +370,25 @@
> DEFINE_XEN_GUEST_HANDLE(xen_hvm_set_ioreq_server_state_t);
> >
> >  #endif /* defined(__XEN__) || defined(__XEN_TOOLS__) */
> >
> > +#if defined(__i386__) || defined(__x86_64__)
> > +
> > +/*
> > + * HVMOP_set_evtchn_upcall_vector: Set a <vector> that should be used
> for event
> > + *                                 channel upcalls on the specified 
> > <vcpu>. If set,
> > + *                                 this vector will be used in preference 
> > to the
> > + *                                 domain global callback via (see
> > + *                                 HVM_PARAM_CALLBACK_IRQ).
> > + */
> > +#define HVMOP_set_evtchn_upcall_vector 23
> > +struct xen_hvm_set_evtchn_upcall_vector {
> > +    uint32_t vcpu;
> > +    uint8_t vector;
> > +};
> > +typedef struct xen_hvm_set_evtchn_upcall_vector
> xen_hvm_set_evtchn_upcall_vector_t;
> > +DEFINE_XEN_GUEST_HANDLE(xen_hvm_set_evtchn_upcall_vector_t);
> 
> I think you should remove "set" from the structure name.  Who knows -
> someone might want to implement a get hypercall in the future.
> 

I didn't want to make any assumption about future use of the structure and 
followed the convention of tying the name to the hypercall. I'm happy to make 
the name more generic if anyone else also thinks that's a good idea.

> Other than that, Reviewed-by: Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>
> 

Thanks,

  Paul

> > +
> > +#endif /* defined(__i386__) || defined(__x86_64__) */
> > +
> >  #endif /* __XEN_PUBLIC_HVM_HVM_OP_H__ */
> >
> >  /*


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