[PATCH 3/4] xen/domctl: Introduce fault_ttl

[Andrew Cooper <andrew.cooper3@citrix.com>]

To inject a simulated resource failure, for testing purposes.

Given a specific set of hypercall parameters, the failure is in a repeatable
position, for the currently booted Xen.  The exact position of failures is
highly dependent on the build of Xen, and hardware support.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Wei Liu <wl@xen.org>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien@xen.org>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
CC: Tamas K Lengyel <tamas@tklengyel.com>

RFC:
 * Probably wants to be Kconfig'd
 * I'm thinking of dropping handle from xen_domctl_createdomain because it's a
   waste of valuable space.
---
 xen/common/dmalloc.c        | 8 +++++++-
 xen/common/domain.c         | 8 ++++++--
 xen/include/public/domctl.h | 1 +
 xen/include/xen/sched.h     | 1 +
 4 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/xen/common/dmalloc.c b/xen/common/dmalloc.c
index e3a0e546c2..1f5d0f5627 100644
--- a/xen/common/dmalloc.c
+++ b/xen/common/dmalloc.c
@@ -10,7 +10,13 @@ void dfree(struct domain *d, void *ptr)
 
 void *_dzalloc(struct domain *d, size_t size, size_t align)
 {
-    void *ptr = _xmalloc(size, align);
+    void *ptr;
+
+    if ( atomic_read(&d->fault_ttl) &&
+         atomic_dec_and_test(&d->fault_ttl) )
+        return NULL;
+
+    ptr = _xmalloc(size, align);
 
     if ( ptr )
         atomic_inc(&d->dalloc_heap);
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 1db1c0e70a..cd73321980 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -427,14 +427,18 @@ struct domain *domain_create(domid_t domid,
     if ( (d = alloc_domain_struct()) == NULL )
         return ERR_PTR(-ENOMEM);
 
-    d->options = config ? config->flags : 0;
-
     /* Sort out our idea of is_system_domain(). */
     d->domain_id = domid;
 
     /* Debug sanity. */
     ASSERT(is_system_domain(d) ? config == NULL : config != NULL);
 
+    if ( config )
+    {
+        d->options = config->flags;
+        atomic_set(&d->fault_ttl, config->fault_ttl);
+    }
+
     /* Sort out our idea of is_control_domain(). */
     d->is_privileged = is_priv;
 
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 666aeb71bf..aaa3d66616 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -48,6 +48,7 @@
 /* XEN_DOMCTL_createdomain */
 struct xen_domctl_createdomain {
     /* IN parameters */
+    uint32_t fault_ttl;
     uint32_t ssidref;
     xen_domain_handle_t handle;
  /* Is this an HVM guest (as opposed to a PV guest)? */
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 8ed8b55a1e..620a9f20e5 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -349,6 +349,7 @@ struct domain
     atomic_t         shr_pages;         /* shared pages */
     atomic_t         paged_pages;       /* paged-out pages */
 
+    atomic_t         fault_ttl;         /* Time until a simulated resource failure. */
     atomic_t         dalloc_heap;       /* Number of xmalloc-like allocations. */
 
     /* Scheduling. */
-- 
2.11.0