Re: [Xen-devel] [PATCH v2 09/12] x86/altp2m: add remaining support routines.

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 24/06/15 18:47, Ed White wrote:
>> > This looks like some hoop jumping around the assertions in
>> > domain_pause() and vcpu_pause().
>> > 
>> > We should probably have some new helpers where the domain needs to be
>> > paused, possibly while in context.  The current domain/vcpu_pause() are
>> > almost always used where it is definitely not safe to pause in context,
>> > hence the assertions.
>> > 
> It is. I'd be happy to use new helpers, I don't feel qualified to
> write them.
>
> Ed

Something like this?  Only compile tested.  In the meantime, I have an
optimisation in mind for domain_pause() on domains with large numbers of
vcpus, but that will have to wait a while.

From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Date: Wed, 24 Jun 2015 19:06:14 +0100
Subject: [PATCH] common/domain: Helpers to pause a domain while in context

For use on codepaths which would need to use domain_pause() but might be in
the target domain's context.  In the case that the target domain is in
context,
all other vcpus are paused.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/common/domain.c     |   28 ++++++++++++++++++++++++++++
 xen/include/xen/sched.h |    5 +++++
 2 files changed, 33 insertions(+)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 3bc52e6..a1d27e3 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1010,6 +1010,34 @@ int domain_unpause_by_systemcontroller(struct
domain *d)
     return 0;
 }
 
+void domain_pause_except_self(struct domain *d)
+{
+    struct vcpu *v, *curr = current;
+
+    if ( curr->domain == d )
+    {
+        for_each_vcpu( d, v )
+            if ( likely(v != curr) )
+                vcpu_pause(v);
+    }
+    else
+        domain_pause(d);
+}
+
+void domain_unpause_except_self(struct domain *d)
+{
+    struct vcpu *v, *curr = current;
+
+    if ( curr->domain == d )
+    {
+        for_each_vcpu( d, v )
+            if ( likely(v != curr) )
+                vcpu_unpause(v);
+    }
+    else
+        domain_unpause(d);
+}
+
 int vcpu_reset(struct vcpu *v)
 {
     struct domain *d = v->domain;
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index b29d9e7..8e1345a 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -804,6 +804,11 @@ static inline int
domain_pause_by_systemcontroller_nosync(struct domain *d)
 {
     return __domain_pause_by_systemcontroller(d, domain_pause_nosync);
 }
+
+/* domain_pause() but safe against trying to pause current. */
+void domain_pause_except_self(struct domain *d);
+void domain_unpause_except_self(struct domain *d);
+
 void cpu_init(void);
 
 struct scheduler;



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