[Xen-changelog] [xen master] x86: allow calling {shadow/hap}_set_allocation with the idle domain

[patchbot@xxxxxxx]

commit 7241fffcd918bce9824b9cca7f90cea1d5689062
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Fri Dec 2 18:07:58 2016 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Dec 2 18:07:58 2016 +0100

    x86: allow calling {shadow/hap}_set_allocation with the idle domain
    
    ... and using the "preempted" parameter. Introduce a new helper that can
    be used from both hypercall or idle vcpu context (ie: during Dom0
    creation) in order to check if preemption is needed. If such preemption
    happens, the caller should then call process_pending_softirqs in order to
    drain the pending softirqs, and then call *_set_allocation again to continue
    with it's execution.
    
    This allows us to call *_set_allocation() when building domain 0.
    
    While there also document hypercall_preempt_check and add an assert to
    local_events_need_delivery in order to be sure it's not called by the idle
    domain, which doesn't receive any events (and that in turn
    hypercall_preempt_check is also not called by the idle domain).
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    Acked-by: Tim Deegan <tim@xxxxxxx>
---
 xen/arch/x86/mm/hap/hap.c       |  2 +-
 xen/arch/x86/mm/shadow/common.c |  2 +-
 xen/include/asm-x86/event.h     |  3 +++
 xen/include/xen/sched.h         | 15 +++++++++++++++
 4 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c
index f099e94..b9faba6 100644
--- a/xen/arch/x86/mm/hap/hap.c
+++ b/xen/arch/x86/mm/hap/hap.c
@@ -379,7 +379,7 @@ hap_set_allocation(struct domain *d, unsigned int pages, 
int *preempted)
             break;
 
         /* Check to see if we need to yield and try again */
-        if ( preempted && hypercall_preempt_check() )
+        if ( preempted && general_preempt_check() )
         {
             *preempted = 1;
             return 0;
diff --git a/xen/arch/x86/mm/shadow/common.c b/xen/arch/x86/mm/shadow/common.c
index 756c276..ddbdb73 100644
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -1681,7 +1681,7 @@ static int sh_set_allocation(struct domain *d,
             break;
 
         /* Check to see if we need to yield and try again */
-        if ( preempted && hypercall_preempt_check() )
+        if ( preempted && general_preempt_check() )
         {
             *preempted = 1;
             return 0;
diff --git a/xen/include/asm-x86/event.h b/xen/include/asm-x86/event.h
index a82062e..d589d6f 100644
--- a/xen/include/asm-x86/event.h
+++ b/xen/include/asm-x86/event.h
@@ -23,6 +23,9 @@ int hvm_local_events_need_delivery(struct vcpu *v);
 static inline int local_events_need_delivery(void)
 {
     struct vcpu *v = current;
+
+    ASSERT(!is_idle_vcpu(v));
+
     return (has_hvm_container_vcpu(v) ? hvm_local_events_need_delivery(v) :
             (vcpu_info(v, evtchn_upcall_pending) &&
              !vcpu_info(v, evtchn_upcall_mask)));
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 1fbda87..063efe6 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -708,11 +708,26 @@ unsigned long hypercall_create_continuation(
     unsigned int op, const char *format, ...);
 void hypercall_cancel_continuation(void);
 
+/*
+ * For long-running operations that must be in hypercall context, check
+ * if there is background work to be done that should interrupt this
+ * operation.
+ */
 #define hypercall_preempt_check() (unlikely(    \
         softirq_pending(smp_processor_id()) |   \
         local_events_need_delivery()            \
     ))
 
+/*
+ * For long-running operations that may be in hypercall context or on
+ * the idle vcpu (e.g. during dom0 construction), check if there is
+ * background work to be done that should interrupt this operation.
+ */
+#define general_preempt_check() (unlikely(                          \
+        softirq_pending(smp_processor_id()) ||                      \
+        (!is_idle_vcpu(current) && local_events_need_delivery())    \
+    ))
+
 extern struct domain *domain_list;
 
 /* Caller must hold the domlist_read_lock or domlist_update_lock. */
--
generated by git-patchbot for /home/xen/git/xen.git#master

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