To allocate the xenstore event channel and initialize the grant table
entry, the xenstore domid is neeed.  A dom0 is craeted 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 and 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.

Signed-off-by: Jason Andryuk <jason.andr...@amd.com>
---
 xen/arch/arm/dom0less-build.c             | 71 +++++++++++++++--------
 xen/arch/arm/domain_build.c               |  1 +
 xen/arch/arm/include/asm/dom0less-build.h |  2 +
 3 files changed, 51 insertions(+), 23 deletions(-)

diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c
index f1d5bbb097..3b8153b05e 100644
--- a/xen/arch/arm/dom0less-build.c
+++ b/xen/arch/arm/dom0less-build.c
@@ -22,6 +22,12 @@
 #include <asm/static-shmem.h>
 
 static domid_t __initdata xs_domid = DOMID_INVALID;
+static bool __initdata need_xenstore;
+
+void __init set_xs_domid(domid_t domid)
+{
+    xs_domid = domid;
+}
 
 bool __init is_dom0less_mode(void)
 {
@@ -697,7 +703,7 @@ 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 )
     {
@@ -755,10 +761,6 @@ static int __init alloc_xenstore_page(struct domain *d)
     interface->connection = XENSTORE_RECONNECT;
     unmap_domain_page(interface);
 
-    if ( xs_domid != DOMID_INVALID )
-        gnttab_seed_entry(d, GNTTAB_RESERVED_XENSTORE, xs_domid,
-                          gfn_x(gfn), GTF_permit_access);
-
     return 0;
 }
 
@@ -767,16 +769,10 @@ 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 )
@@ -848,6 +844,34 @@ static void __init domain_vcpu_affinity(struct domain *d,
     }
 }
 
+static void __init initialize_domU_xenstore(void)
+{
+    struct domain *d;
+
+    if ( xs_domid == DOMID_INVALID )
+        return;
+
+    for_each_domain( d )
+    {
+        unsigned long 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);
+
+        if ( gfn != ~0ULL )
+            gnttab_seed_entry(d, GNTTAB_RESERVED_XENSTORE, xs_domid,
+                              gfn, GTF_permit_access);
+    }
+}
+
 static int __init construct_domU(struct domain *d,
                                  const struct dt_device_node *node)
 {
@@ -888,17 +912,13 @@ 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;
@@ -1181,8 +1201,13 @@ void __init create_domUs(void)
                   dt_node_name(node), rc);
 
         if ( d_cfg.flags & XEN_DOMCTL_CDF_xs_domain )
-            xs_domid = d->domain_id;
+            set_xs_domid(d->domain_id);
     }
+
+    if ( need_xenstore && xs_domid == DOMID_INVALID )
+        panic("xenstore requested, but xenstore domain not present\n");
+
+    initialize_domU_xenstore();
 }
 
 /*
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 00bc484642..ba6bbb95c1 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2373,6 +2373,7 @@ void __init create_dom0(void)
     unsigned int flags = CDF_privileged | CDF_hardware;
     int rc;
 
+    set_xs_domid(0);
     /* The vGIC for DOM0 is exactly emulating the hardware GIC */
     dom0_cfg.arch.gic_version = XEN_DOMCTL_CONFIG_GIC_NATIVE;
     /*
diff --git a/xen/arch/arm/include/asm/dom0less-build.h 
b/xen/arch/arm/include/asm/dom0less-build.h
index 5864944bda..df879f93c8 100644
--- a/xen/arch/arm/include/asm/dom0less-build.h
+++ b/xen/arch/arm/include/asm/dom0less-build.h
@@ -9,6 +9,7 @@
 
 void create_domUs(void);
 bool is_dom0less_mode(void);
+void set_xs_domid(domid_t);
 
 #else /* !CONFIG_DOM0LESS_BOOT */
 
@@ -17,6 +18,7 @@ static inline bool is_dom0less_mode(void)
 {
     return false;
 }
+static inline void set_xs_domid(domid_t) {}
 
 #endif /* CONFIG_DOM0LESS_BOOT */
 
-- 
2.48.1


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