Re: [PATCH 1/2] xen: Introduce PHYSDEVOP_pirq_eoi_gmfn_new

[Keir Fraser <keir@xen.org>]

On 26/01/2012 15:49, "Stefano Stabellini" <Stefano.Stabellini@eu.citrix.com>
wrote:

> PHYSDEVOP_pirq_eoi_gmfn changes the semantics of PHYSDEVOP_eoi.
> Introduce PHYSDEVOP_pirq_eoi_gmfn_new, that is like
> PHYSDEVOP_pirq_eoi_gmfn but it doesn't modify the behaviour of another
> hypercall.

It's nasty that pirq_eoi_gmfn has the side effect. I suggest add a PHYSDEVOP
to explicitly enable/disable unmask-on-eoi (i.e., the command accepts a
boolean parameter). Once it is explicitly enabled/disabled in this way,
pirq_eoi_gmfn no longer has the side effect (regardless of whether it is
called before or after the explicit setting). So e.g., pv_domain.auto_unmask
becomes an int where 0/1 means no/yes, and -1 means default (i.e., old
behavour where it depends on whether PHYSDEVOP_pirq_eoi_gmfn has been
called).

This seems to me to move a bad interface in a better direction.

 -- Keir

> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> ---
>  xen/arch/ia64/xen/domain.c    |    1 +
>  xen/arch/ia64/xen/hypercall.c |    5 ++++-
>  xen/arch/x86/domain.c         |    1 +
>  xen/arch/x86/physdev.c        |    6 +++++-
>  xen/include/asm-ia64/domain.h |    3 +++
>  xen/include/asm-x86/domain.h  |    3 +++
>  xen/include/public/physdev.h  |    8 ++++++++
>  7 files changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/ia64/xen/domain.c b/xen/arch/ia64/xen/domain.c
> index 1ea5a90..a31bd32 100644
> --- a/xen/arch/ia64/xen/domain.c
> +++ b/xen/arch/ia64/xen/domain.c
> @@ -1731,6 +1731,7 @@ int domain_relinquish_resources(struct domain *d)
> if (d->arch.pirq_eoi_map != NULL) {
> put_page(virt_to_page(d->arch.pirq_eoi_map));
> d->arch.pirq_eoi_map = NULL;
> +   d->arch.auto_unmask = 0;
> }
>  
> /* Tear down shadow mode stuff. */
> diff --git a/xen/arch/ia64/xen/hypercall.c b/xen/arch/ia64/xen/hypercall.c
> index 130675e..44c3407 100644
> --- a/xen/arch/ia64/xen/hypercall.c
> +++ b/xen/arch/ia64/xen/hypercall.c
> @@ -65,7 +65,7 @@ static long __do_pirq_guest_eoi(struct domain *d, int pirq)
>  {
> if ( pirq < 0 || pirq >= NR_IRQS )
> return -EINVAL;
> - if ( d->arch.pirq_eoi_map ) {
> + if ( d->arch.pirq_eoi_map  && d->arch.auto_unmask ) {
> spin_lock(&d->event_lock);
> evtchn_unmask(pirq_to_evtchn(d, pirq));
> spin_unlock(&d->event_lock);
> @@ -508,6 +508,7 @@ long do_physdev_op(int cmd, XEN_GUEST_HANDLE(void) arg)
>          break;
>      }
>  
> +    case PHYSDEVOP_pirq_eoi_gmfn_new:
>      case PHYSDEVOP_pirq_eoi_gmfn: {
>          struct physdev_pirq_eoi_gmfn info;
>          unsigned long mfn;
> @@ -531,6 +532,8 @@ long do_physdev_op(int cmd, XEN_GUEST_HANDLE(void) arg)
>          }
>  
>          current->domain->arch.pirq_eoi_map = mfn_to_virt(mfn);
> +  if ( cmd == PHYSDEVOP_pirq_eoi_gmfn )
> +   current->domain->arch.auto_unmask = 1;
>          ret = 0;
>          break;
>      }
> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> index 61d83c8..a540af7 100644
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -2125,6 +2125,7 @@ int domain_relinquish_resources(struct domain *d)
>                  put_page_and_type(
>                      mfn_to_page(d->arch.pv_domain.pirq_eoi_map_mfn));
>                  d->arch.pv_domain.pirq_eoi_map = NULL;
> +                d->arch.pv_domain.auto_unmask = 0;
>              }
>          }
>  
> diff --git a/xen/arch/x86/physdev.c b/xen/arch/x86/physdev.c
> index f280c28..efd517f 100644
> --- a/xen/arch/x86/physdev.c
> +++ b/xen/arch/x86/physdev.c
> @@ -271,7 +271,8 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE(void) arg)
>              break;
>          }
>          if ( !is_hvm_domain(v->domain) &&
> -             v->domain->arch.pv_domain.pirq_eoi_map )
> +             v->domain->arch.pv_domain.pirq_eoi_map &&
> +             v->domain->arch.pv_domain.auto_unmask )
>              evtchn_unmask(pirq->evtchn);
>          if ( !is_hvm_domain(v->domain) ||
>               domain_pirq_to_irq(v->domain, eoi.irq) > 0 )
> @@ -293,6 +294,7 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE(void) arg)
>          break;
>      }
>  
> +    case PHYSDEVOP_pirq_eoi_gmfn_new:
>      case PHYSDEVOP_pirq_eoi_gmfn: {
>          struct physdev_pirq_eoi_gmfn info;
>          unsigned long mfn;
> @@ -329,6 +331,8 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE(void) arg)
>              ret = -ENOSPC;
>              break;
>          }
> +        if ( cmd == PHYSDEVOP_pirq_eoi_gmfn )
> +            v->domain->arch.pv_domain.auto_unmask = 1;
>  
>          put_gfn(current->domain, info.gmfn);
>          ret = 0;
> diff --git a/xen/include/asm-ia64/domain.h b/xen/include/asm-ia64/domain.h
> index 12dc3bd..8163d67 100644
> --- a/xen/include/asm-ia64/domain.h
> +++ b/xen/include/asm-ia64/domain.h
> @@ -186,6 +186,9 @@ struct arch_domain {
>      /* Shared page for notifying that explicit PIRQ EOI is required. */
>      unsigned long *pirq_eoi_map;
>      unsigned long pirq_eoi_map_mfn;
> + /* set auto_unmask to 1 if you want PHYSDEVOP_eoi to automatically
> +  * unmask the event channel */
> + unsigned int auto_unmask;
>  
>      /* Address of efi_runtime_services_t (placed in domain memory)  */
>      void *efi_runtime;
> diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
> index 00bbaeb..b0cbe65 100644
> --- a/xen/include/asm-x86/domain.h
> +++ b/xen/include/asm-x86/domain.h
> @@ -231,6 +231,9 @@ struct pv_domain
>      /* Shared page for notifying that explicit PIRQ EOI is required. */
>      unsigned long *pirq_eoi_map;
>      unsigned long pirq_eoi_map_mfn;
> +    /* set auto_unmask to 1 if you want PHYSDEVOP_eoi to automatically
> +     * unmask the event channel */
> +    unsigned int auto_unmask;
>  
>      /* Pseudophysical e820 map (XENMEM_memory_map).  */
>      spinlock_t e820_lock;
> diff --git a/xen/include/public/physdev.h b/xen/include/public/physdev.h
> index 6e23295..d555719 100644
> --- a/xen/include/public/physdev.h
> +++ b/xen/include/public/physdev.h
> @@ -50,6 +50,14 @@ DEFINE_XEN_GUEST_HANDLE(physdev_eoi_t);
>   * array indexed by Xen's PIRQ value.
>   */
>  #define PHYSDEVOP_pirq_eoi_gmfn         17
> +/*
> + * Register a shared page for the hypervisor to indicate whether the
> + * guest must issue PHYSDEVOP_eoi. This hypercall is very similar to
> + * PHYSDEVOP_pirq_eoi_gmfn but it doesn't change the semantics of
> + * PHYSDEVOP_eoi. The page registered is used as a bit array indexed by
> + * Xen's PIRQ value.
> + */
> +#define PHYSDEVOP_pirq_eoi_gmfn_new         28
>  struct physdev_pirq_eoi_gmfn {
>      /* IN */
>      xen_pfn_t gmfn;