[PATCH v7 11/12] xen/arm: add sve property for dom0less domUs

[Luca Fancellu <luca.fancellu@xxxxxxx>]

Add a device tree property in the dom0less domU configuration
to enable the guest to use SVE.

Update documentation.

Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
---
Changes from v6:
 - Use ifdef in create_domUs and fail if 'sve' is used on systems
   with CONFIG_ARM64_SVE not selected (Bertrand, Julien, Jan)
Changes from v5:
 - Stop the domain creation if SVE not supported or SVE VL
   errors (Julien, Bertrand)
 - now sve_sanitize_vl_param is renamed to sve_domctl_vl_param
   and returns a boolean, change the affected code.
 - Reworded documentation.
Changes from v4:
 - Now it is possible to specify the property "sve" for dom0less
   device tree node without any value, that means the platform
   supported VL will be used.
Changes from v3:
 - Now domainconfig_encode_vl is named sve_encode_vl
Changes from v2:
 - xen_domctl_createdomain field name has changed into sve_vl
   and its value is the VL/128, use domainconfig_encode_vl
   to encode a plain VL in bits.
Changes from v1:
 - No changes
Changes from RFC:
 - Changed documentation
---
 docs/misc/arm/device-tree/booting.txt | 16 +++++++++++++++
 xen/arch/arm/domain_build.c           | 28 +++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/docs/misc/arm/device-tree/booting.txt 
b/docs/misc/arm/device-tree/booting.txt
index 3879340b5e0a..32a0e508c471 100644
--- a/docs/misc/arm/device-tree/booting.txt
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -193,6 +193,22 @@ with the following properties:
     Optional. Handle to a xen,cpupool device tree node that identifies the
     cpupool where the guest will be started at boot.
 
+- sve
+
+    Optional. The `sve` property enables Arm SVE usage for the domain and sets
+    the maximum SVE vector length, the option is applicable only to AArch64
+    guests.
+    A value equal to 0 disables the feature, this is the default value.
+    Specifying this property with no value, means that the SVE vector length
+    will be set equal to the maximum vector length supported by the platform.
+    Values above 0 explicitly set the maximum SVE vector length for the domain,
+    allowed values are from 128 to maximum 2048, being multiple of 128.
+    Please note that when the user explicitly specifies the value, if that 
value
+    is above the hardware supported maximum SVE vector length, the domain
+    creation will fail and the system will stop, the same will occur if the
+    option is provided with a non zero value, but the platform doesn't support
+    SVE.
+
 - xen,enhanced
 
     A string property. Possible property values are:
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 9202a96d9c28..ba4fe9e165ee 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -4008,6 +4008,34 @@ void __init create_domUs(void)
             d_cfg.max_maptrack_frames = val;
         }
 
+        if ( dt_get_property(node, "sve", &val) )
+        {
+#ifdef CONFIG_ARM64_SVE
+            unsigned int sve_vl_bits;
+            bool ret = false;
+
+            if ( !val )
+            {
+                /* Property found with no value, means max HW VL supported */
+                ret = sve_domctl_vl_param(-1, &sve_vl_bits);
+            }
+            else
+            {
+                if ( dt_property_read_u32(node, "sve", &val) )
+                    ret = sve_domctl_vl_param(val, &sve_vl_bits);
+                else
+                    panic("Error reading 'sve' property");
+            }
+
+            if ( ret )
+                d_cfg.arch.sve_vl = sve_encode_vl(sve_vl_bits);
+            else
+                panic("SVE vector length error\n");
+#else
+            panic("'sve' property found, but CONFIG_ARM64_SVE not selected");
+#endif
+        }
+
         /*
          * The variable max_init_domid is initialized with zero, so here it's
          * very important to use the pre-increment operator to call
-- 
2.34.1