[XEN PATCH v2 1/5] xen: introduce xen,enhanced dom0less property

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>

Introduce a new "xen,enhanced" dom0less property to enable/disable PV
driver interfaces for dom0less guests. Currently only "enabled" and
"disabled" are supported property values (and empty). Leave the option
open to implement further possible values in the future (e.g.
"xenstore" to enable only xenstore.)

This patch only parses the property. Next patches will make use of it.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
---
Changes in v2:
- rename kinfo.enhanced to kinfo.dom0less_enhanced
- set kinfo.dom0less_enhanced to true for dom0
- handle -ENODATA in addition to -EILSEQ
---
 docs/misc/arm/device-tree/booting.txt | 18 ++++++++++++++++++
 xen/arch/arm/domain_build.c           |  8 ++++++++
 xen/arch/arm/include/asm/kernel.h     |  3 +++
 3 files changed, 29 insertions(+)

diff --git a/docs/misc/arm/device-tree/booting.txt 
b/docs/misc/arm/device-tree/booting.txt
index 71895663a4..38c29fb3d8 100644
--- a/docs/misc/arm/device-tree/booting.txt
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -169,6 +169,24 @@ with the following properties:
     Please note that the SPI used for the virtual pl011 could clash with the
     physical SPI of a physical device assigned to the guest.
 
+- xen,enhanced
+
+    A string property. Possible property values are:
+
+    - "enabled" (or missing property value)
+    Xen PV interfaces, including grant-table and xenstore, will be
+    enabled for the VM.
+
+    - "disabled"
+    Xen PV interfaces are disabled.
+
+    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.
+
+    In the future other possible property values might be added to
+    enable only selected interfaces.
+
 - nr_spis
 
     Optional. A 32-bit integer specifying the number of SPIs (Shared
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 6931c022a2..9144d6c0b6 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2963,6 +2963,7 @@ static int __init construct_domU(struct domain *d,
                                  const struct dt_device_node *node)
 {
     struct kernel_info kinfo = {};
+    const char *dom0less_enhanced;
     int rc;
     u64 mem;
 
@@ -2978,6 +2979,12 @@ static int __init construct_domU(struct domain *d,
 
     kinfo.vpl011 = dt_property_read_bool(node, "vpl011");
 
+    rc = dt_property_read_string(node, "xen,enhanced", &dom0less_enhanced);
+    if ( rc == -EILSEQ ||
+         rc == -ENODATA ||
+         (rc == 0 && !strcmp(dom0less_enhanced, "enabled")) )
+        kinfo.dom0less_enhanced = true;
+
     if ( vcpu_create(d, 0) == NULL )
         return -ENOMEM;
 
@@ -3095,6 +3102,7 @@ static int __init construct_dom0(struct domain *d)
 
     kinfo.unassigned_mem = dom0_mem;
     kinfo.d = d;
+    kinfo.dom0less_enhanced = true;
 
     rc = kernel_probe(&kinfo, NULL);
     if ( rc < 0 )
diff --git a/xen/arch/arm/include/asm/kernel.h 
b/xen/arch/arm/include/asm/kernel.h
index 874aa108a7..c4dc039b54 100644
--- a/xen/arch/arm/include/asm/kernel.h
+++ b/xen/arch/arm/include/asm/kernel.h
@@ -36,6 +36,9 @@ struct kernel_info {
     /* Enable pl011 emulation */
     bool vpl011;
 
+    /* Enable PV drivers */
+    bool dom0less_enhanced;
+
     /* GIC phandle */
     uint32_t phandle_gic;
 
-- 
2.25.1