[xen staging] xen/arm: introduce new xen,enhanced property value

[patchbot@xxxxxxx]

commit 4a6d155a840de41e59050e2dc06d86293112c0f3
Author:     Rahul Singh <rahul.singh@xxxxxxx>
AuthorDate: Wed Sep 7 17:27:37 2022 +0100
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Thu Sep 8 12:21:59 2022 +0100

    xen/arm: introduce new xen,enhanced property value
    
    Introduce a new "xen,enhanced" dom0less property value "no-xenstore" to
    disable xenstore interface for dom0less guests.
    
    Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 docs/misc/arm/device-tree/booting.txt |  4 ++++
 xen/arch/arm/domain_build.c           | 10 ++++++----
 xen/arch/arm/include/asm/kernel.h     | 23 +++++++++++++++++++++--
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/docs/misc/arm/device-tree/booting.txt 
b/docs/misc/arm/device-tree/booting.txt
index 98253414b8..47567b3906 100644
--- a/docs/misc/arm/device-tree/booting.txt
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -204,6 +204,10 @@ with the following properties:
     - "disabled"
     Xen PV interfaces are disabled.
 
+    - "no-xenstore"
+    All default Xen PV interfaces, including grant-table will be enabled but
+    xenstore will be disabled for the VM.
+
     If the xen,enhanced property is present with no value, it defaults
     to "enabled". If the xen,enhanced property is not present, PV
     interfaces are disabled.
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 7192293068..e5aba9841f 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2891,7 +2891,7 @@ static int __init prepare_dtb_domU(struct domain *d, 
struct kernel_info *kinfo)
             goto err;
     }
 
-    if ( kinfo->dom0less_enhanced )
+    if ( kinfo->dom0less_feature & DOM0LESS_ENHANCED_NO_XS )
     {
         ret = make_hypervisor_node(d, kinfo, addrcells, sizecells);
         if ( ret )
@@ -3209,10 +3209,12 @@ static int __init construct_domU(struct domain *d,
          (rc == 0 && !strcmp(dom0less_enhanced, "enabled")) )
     {
         if ( hardware_domain )
-            kinfo.dom0less_enhanced = true;
+            kinfo.dom0less_feature = DOM0LESS_ENHANCED;
         else
-            panic("Tried to use xen,enhanced without dom0\n");
+            panic("At the moment, Xenstore support requires dom0 to be 
present\n");
     }
+    else if ( rc == 0 && !strcmp(dom0less_enhanced, "no-xenstore") )
+        kinfo.dom0less_feature = DOM0LESS_ENHANCED_NO_XS;
 
     if ( vcpu_create(d, 0) == NULL )
         return -ENOMEM;
@@ -3252,7 +3254,7 @@ static int __init construct_domU(struct domain *d,
     if ( rc < 0 )
         return rc;
 
-    if ( kinfo.dom0less_enhanced )
+    if ( kinfo.dom0less_feature & DOM0LESS_XENSTORE )
     {
         ASSERT(hardware_domain);
         rc = alloc_xenstore_evtchn(d);
diff --git a/xen/arch/arm/include/asm/kernel.h 
b/xen/arch/arm/include/asm/kernel.h
index c4dc039b54..f8bb85767b 100644
--- a/xen/arch/arm/include/asm/kernel.h
+++ b/xen/arch/arm/include/asm/kernel.h
@@ -9,6 +9,25 @@
 #include <xen/device_tree.h>
 #include <asm/setup.h>
 
+/*
+ * List of possible features for dom0less domUs
+ *
+ * DOM0LESS_ENHANCED_NO_XS: Notify the OS it is running on top of Xen. All the
+ *                          default features (excluding Xenstore) will be
+ *                          available. Note that an OS *must* not rely on the
+ *                          availability of Xen features if this is not set.
+ * DOM0LESS_XENSTORE:       Xenstore will be enabled for the VM. This feature
+ *                          can't be enabled without the
+ *                          DOM0LESS_ENHANCED_NO_XS.
+ * DOM0LESS_ENHANCED:       Notify the OS it is running on top of Xen. All the
+ *                          default features (including Xenstore) will be
+ *                          available. Note that an OS *must* not rely on the
+ *                          availability of Xen features if this is not set.
+ */
+#define DOM0LESS_ENHANCED_NO_XS  BIT(0, U)
+#define DOM0LESS_XENSTORE        BIT(1, U)
+#define DOM0LESS_ENHANCED        (DOM0LESS_ENHANCED_NO_XS | DOM0LESS_XENSTORE)
+
 struct kernel_info {
 #ifdef CONFIG_ARM_64
     enum domain_type type;
@@ -36,8 +55,8 @@ struct kernel_info {
     /* Enable pl011 emulation */
     bool vpl011;
 
-    /* Enable PV drivers */
-    bool dom0less_enhanced;
+    /* Enable/Disable PV drivers interfaces */
+    uint16_t dom0less_feature;
 
     /* GIC phandle */
     uint32_t phandle_gic;
--
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