xen/arm: dom0less delay xenstore initialization

To allocate the xenstore event channel and initialize the grant table
entry, the xenstore domid is neeed.  A dom0 is created before the domUs,
so it is normally available through hardware_domain.  With capabilities
and dom0less, the xenstore domain may not be created first.

Keep the population of the page and HVM_PARAM_STORE_PFN in the normal
domain construction, but delay event channel creation and grant seeding
to after all domUs are created.  HVM_PARAM_STORE_PFN now serves as
indication to setup xenstore since the device tree is no longer
immediately available.  0 means no xenstore.  ~0ULL means legacy so only
the event channel needs setup, and any other value means to seed the
page.

dom0 needs to set xs_domid when it is serving as the xenstore domain.

The domain running xenstored needs to be the handler for VIRQ_DOM_EXC,
so set that as well - it otherwise defaults to hardware domain.

Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/dom0less-build.c

@@ -20,6 +20,15 @@
 #include <asm/static-memory.h>
 #include <asm/static-shmem.h>
 
+static domid_t __initdata xs_domid = DOMID_INVALID;
+static bool __initdata need_xenstore;
+
+void __init set_xs_domain(struct domain *d)
+{
+    xs_domid = d->domain_id;
+    set_global_virq_handler(d, VIRQ_DOM_EXC);
+}
+
 bool __init is_dom0less_mode(void)
 {
     struct bootmodules *mods = &bootinfo.modules;
@@ -679,7 +688,7 @@ static int __init alloc_xenstore_evtchn(struct domain *d)
     int rc;
 
     alloc.dom = d->domain_id;
-    alloc.remote_dom = hardware_domain->domain_id;
+    alloc.remote_dom = xs_domid;
     rc = evtchn_alloc_unbound(&alloc, 0);
     if ( rc )
     {
@@ -745,16 +754,10 @@ static int __init alloc_xenstore_params(struct kernel_info *kinfo)
     struct domain *d = kinfo->d;
     int rc = 0;
 
-    if ( kinfo->dom0less_feature & (DOM0LESS_XENSTORE | DOM0LESS_XS_LEGACY) )
-    {
-        ASSERT(hardware_domain);
-        rc = alloc_xenstore_evtchn(d);
-        if ( rc < 0 )
-            return rc;
+    if ( (kinfo->dom0less_feature & (DOM0LESS_XENSTORE | DOM0LESS_XS_LEGACY))
+                                 == (DOM0LESS_XENSTORE | DOM0LESS_XS_LEGACY) )
         d->arch.hvm.params[HVM_PARAM_STORE_PFN] = ~0ULL;
-    }
-
-    if ( kinfo->dom0less_feature & DOM0LESS_XENSTORE )
+    else if ( kinfo->dom0less_feature & DOM0LESS_XENSTORE )
     {
         rc = alloc_xenstore_page(d);
         if ( rc < 0 )
@@ -764,6 +767,30 @@ static int __init alloc_xenstore_params(struct kernel_info *kinfo)
     return rc;
 }
 
+static void __init initialize_domU_xenstore(void)
+{
+    struct domain *d;
+
+    if ( xs_domid == DOMID_INVALID )
+        return;
+
+    for_each_domain( d )
+    {
+        uint64_t gfn = d->arch.hvm.params[HVM_PARAM_STORE_PFN];
+        int rc;
+
+        if ( gfn == 0 )
+            continue;
+
+        if ( is_xenstore_domain(d) )
+            continue;
+
+        rc = alloc_xenstore_evtchn(d);
+        if ( rc < 0 )
+            panic("%pd: Failed to allocate xenstore_evtchn\n", d);
+    }
+}
+
 static void __init domain_vcpu_affinity(struct domain *d,
                                         const struct dt_device_node *node)
 {
@@ -899,17 +926,13 @@ static int __init construct_domU(struct domain *d,
          rc == -ENODATA ||
          (rc == 0 && !strcmp(dom0less_enhanced, "enabled")) )
     {
-        if ( hardware_domain )
-            kinfo.dom0less_feature = DOM0LESS_ENHANCED;
-        else
-            panic("At the moment, Xenstore support requires dom0 to be present\n");
+        need_xenstore = true;
+        kinfo.dom0less_feature = DOM0LESS_ENHANCED;
     }
     else if ( rc == 0 && !strcmp(dom0less_enhanced, "legacy") )
     {
-        if ( hardware_domain )
-            kinfo.dom0less_feature = DOM0LESS_ENHANCED_LEGACY;
-        else
-            panic("At the moment, Xenstore support requires dom0 to be present\n");
+        need_xenstore = true;
+        kinfo.dom0less_feature = DOM0LESS_ENHANCED_LEGACY;
     }
     else if ( rc == 0 && !strcmp(dom0less_enhanced, "no-xenstore") )
         kinfo.dom0less_feature = DOM0LESS_ENHANCED_NO_XS;
@@ -1156,7 +1179,15 @@ void __init create_domUs(void)
         if ( rc )
             panic("Could not set up domain %s (rc = %d)\n",
                   dt_node_name(node), rc);
+
+        if ( d_cfg.flags & XEN_DOMCTL_CDF_xs_domain )
+            set_xs_domain(d);
     }
+
+    if ( need_xenstore && xs_domid == DOMID_INVALID )
+        panic("xenstore requested, but xenstore domain not present\n");
+
+    initialize_domU_xenstore();
 }
 
 /*

xen/arch/arm/domain_build.c

@@ -2408,6 +2408,8 @@ void __init create_dom0(void)
     rc = construct_dom0(dom0);
     if ( rc )
         panic("Could not set up DOM0 guest OS (rc = %d)\n", rc);
+
+    set_xs_domain(dom0);
 }
 
 /*

xen/arch/arm/include/asm/dom0less-build.h

@@ -9,6 +9,7 @@
 
 void create_domUs(void);
 bool is_dom0less_mode(void);
+void set_xs_domain(struct domain *d);
 
 #else /* !CONFIG_DOM0LESS_BOOT */
 
@@ -17,6 +18,7 @@ static inline bool is_dom0less_mode(void)
 {
     return false;
 }
+static inline void set_xs_domain(struct domain *d) {}
 
 #endif /* CONFIG_DOM0LESS_BOOT */