On 04/03/14 11:26, Jan Beulich wrote:
> - never preempt on the first iteration (ensure forward progress)
> - never preempt on the last iteration (pointless/wasteful)
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

>
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -2934,7 +2934,7 @@ long do_mmuext_op(
>  
>      for ( i = 0; i < count; i++ )
>      {
> -        if ( curr->arch.old_guest_table || hypercall_preempt_check() )
> +        if ( curr->arch.old_guest_table || (i && hypercall_preempt_check()) )
>          {
>              rc = -EAGAIN;
>              break;
> @@ -3481,7 +3481,7 @@ long do_mmu_update(
>  
>      for ( i = 0; i < count; i++ )
>      {
> -        if ( curr->arch.old_guest_table || hypercall_preempt_check() )
> +        if ( curr->arch.old_guest_table || (i && hypercall_preempt_check()) )
>          {
>              rc = -EAGAIN;
>              break;
> --- a/xen/arch/x86/mm/hap/hap.c
> +++ b/xen/arch/x86/mm/hap/hap.c
> @@ -326,7 +326,7 @@ hap_set_allocation(struct domain *d, uns
>      else
>          pages -= d->arch.paging.hap.p2m_pages;
>  
> -    while ( d->arch.paging.hap.total_pages != pages )
> +    for ( ; ; )
>      {
>          if ( d->arch.paging.hap.total_pages < pages )
>          {
> @@ -355,6 +355,8 @@ hap_set_allocation(struct domain *d, uns
>              d->arch.paging.hap.total_pages--;
>              free_domheap_page(pg);
>          }
> +        else
> +            break;
>  
>          /* Check to see if we need to yield and try again */
>          if ( preempted && hypercall_preempt_check() )
> --- a/xen/arch/x86/mm/p2m-pod.c
> +++ b/xen/arch/x86/mm/p2m-pod.c
> @@ -242,7 +242,8 @@ p2m_pod_set_cache_target(struct p2m_doma
>  
>          p2m_pod_cache_add(p2m, page, order);
>  
> -        if ( hypercall_preempt_check() && preemptible )
> +        if ( preemptible && pod_target != p2m->pod.count &&
> +             hypercall_preempt_check() )
>          {
>              ret = -EAGAIN;
>              goto out;
> @@ -286,7 +287,8 @@ p2m_pod_set_cache_target(struct p2m_doma
>  
>              put_page(page+i);
>  
> -            if ( hypercall_preempt_check() && preemptible )
> +            if ( preemptible && pod_target != p2m->pod.count &&
> +                 hypercall_preempt_check() )
>              {
>                  ret = -EAGAIN;
>                  goto out;
> --- a/xen/arch/x86/mm/shadow/common.c
> +++ b/xen/arch/x86/mm/shadow/common.c
> @@ -1672,7 +1672,7 @@ static unsigned int sh_set_allocation(st
>      SHADOW_PRINTK("current %i target %i\n", 
>                     d->arch.paging.shadow.total_pages, pages);
>  
> -    while ( d->arch.paging.shadow.total_pages != pages ) 
> +    for ( ; ; )
>      {
>          if ( d->arch.paging.shadow.total_pages < pages ) 
>          {
> @@ -1707,6 +1707,8 @@ static unsigned int sh_set_allocation(st
>              d->arch.paging.shadow.total_pages--;
>              free_domheap_page(sp);
>          }
> +        else
> +            break;
>  
>          /* Check to see if we need to yield and try again */
>          if ( preempted && hypercall_preempt_check() )
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -3596,13 +3596,6 @@ long do_set_trap_table(XEN_GUEST_HANDLE_
>  
>      for ( ; ; )
>      {
> -        if ( hypercall_preempt_check() )
> -        {
> -            rc = hypercall_create_continuation(
> -                __HYPERVISOR_set_trap_table, "h", traps);
> -            break;
> -        }
> -
>          if ( copy_from_guest(&cur, traps, 1) )
>          {
>              rc = -EFAULT;
> @@ -3623,6 +3616,13 @@ long do_set_trap_table(XEN_GUEST_HANDLE_
>              init_int80_direct_trap(curr);
>  
>          guest_handle_add_offset(traps, 1);
> +
> +        if ( hypercall_preempt_check() )
> +        {
> +            rc = hypercall_create_continuation(
> +                __HYPERVISOR_set_trap_table, "h", traps);
> +            break;
> +        }
>      }
>  
>      return rc;
> --- a/xen/arch/x86/x86_64/compat/traps.c
> +++ b/xen/arch/x86/x86_64/compat/traps.c
> @@ -329,13 +329,6 @@ int compat_set_trap_table(XEN_GUEST_HAND
>  
>      for ( ; ; )
>      {
> -        if ( hypercall_preempt_check() )
> -        {
> -            rc = hypercall_create_continuation(
> -                __HYPERVISOR_set_trap_table, "h", traps);
> -            break;
> -        }
> -
>          if ( copy_from_guest(&cur, traps, 1) )
>          {
>              rc = -EFAULT;
> @@ -353,6 +346,13 @@ int compat_set_trap_table(XEN_GUEST_HAND
>              init_int80_direct_trap(current);
>  
>          guest_handle_add_offset(traps, 1);
> +
> +        if ( hypercall_preempt_check() )
> +        {
> +            rc = hypercall_create_continuation(
> +                __HYPERVISOR_set_trap_table, "h", traps);
> +            break;
> +        }
>      }
>  
>      return rc;
>
>
>
>
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