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[PATCH v4 6/7] xen/arm: introduce new xen,enhanced property value

Rahul Singh posted 7 patches 3 years, 5 months ago
Only 6 patches received!
There is a newer version of this series
[PATCH v4 6/7] xen/arm: introduce new xen,enhanced property value
Posted by Rahul Singh 3 years, 5 months ago 
Introduce a new "xen,enhanced" dom0less property value "no-xenstore" to
disable xenstore interface for dom0less guests.

Signed-off-by: Rahul Singh <rahul.singh@arm.com>
---
Changes in v4:
 - Implement defines for dom0less features
Changes in v3:
 - new patch in this version
---
 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..1b0dca1454 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
+    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 707e247f6a..0b164ef595 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..ad240494ea 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 interface,grant table, evtchn or xenstore */
+    uint32_t dom0less_feature;
 
     /* GIC phandle */
     uint32_t phandle_gic;
-- 
2.25.1
Re: [PATCH v4 6/7] xen/arm: introduce new xen,enhanced property value
Posted by Julien Grall 3 years, 5 months ago 
Hi Rahul

On 06/09/2022 14:40, Rahul Singh wrote:
> Introduce a new "xen,enhanced" dom0less property value "no-xenstore" to
> disable xenstore interface for dom0less guests.
> 
> Signed-off-by: Rahul Singh <rahul.singh@arm.com>
> ---
> Changes in v4:
>   - Implement defines for dom0less features
> Changes in v3:
>   - new patch in this version
> ---
>   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..1b0dca1454 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
> +    Xen PV interfaces, including grant-table will be enabled but xenstore

Please use "All default" in front. So it is clear that everything is 
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 707e247f6a..0b164ef595 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..ad240494ea 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 interface,grant table, evtchn or xenstore */

The part after "," is technically wrong because it also affects other 
interfaces. But I would drop it to avoid any stale comment (we may add 
new one in the futures).

Cheers,

-- 
Julien Grall
Re: [PATCH v4 6/7] xen/arm: introduce new xen,enhanced property value
Posted by Rahul Singh 3 years, 5 months ago 
Hi Julien,

> On 7 Sep 2022, at 2:09 pm, Julien Grall <julien@xen.org> wrote:
> 
> Hi Rahul
> 
> On 06/09/2022 14:40, Rahul Singh wrote:
>> Introduce a new "xen,enhanced" dom0less property value "no-xenstore" to
>> disable xenstore interface for dom0less guests.
>> Signed-off-by: Rahul Singh <rahul.singh@arm.com>
>> ---
>> Changes in v4:
>>  - Implement defines for dom0less features
>> Changes in v3:
>>  - new patch in this version
>> ---
>>  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..1b0dca1454 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
>> +    Xen PV interfaces, including grant-table will be enabled but xenstore
> 
> Please use "All default" in front. So it is clear that everything is enabled but xenstore.

Ack. 
> 
>> +    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 707e247f6a..0b164ef595 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..ad240494ea 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 interface,grant table, evtchn or xenstore */
> 
> The part after "," is technically wrong because it also affects other interfaces. But I would drop it to avoid any stale comment (we may add new one in the futures).

Ok . I will remove and will comment like this:
/* Enable/Disable PV drivers interfaces */
 
Regards,
Rahul
Re: [PATCH v4 6/7] xen/arm: introduce new xen,enhanced property value
Posted by Stefano Stabellini 3 years, 5 months ago 
On Tue, 6 Sep 2022, Rahul Singh wrote:
> Introduce a new "xen,enhanced" dom0less property value "no-xenstore" to
> disable xenstore interface for dom0less guests.
> 
> Signed-off-by: Rahul Singh <rahul.singh@arm.com>
> ---
> Changes in v4:
>  - Implement defines for dom0less features
> Changes in v3:
>  - new patch in this version
> ---
>  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..1b0dca1454 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
> +    Xen PV interfaces, including grant-table will be enabled but xenstore
> +    will be disabled for the VM.

Please use "" for consistency:

    - "no-xenstore"


>      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 707e247f6a..0b164ef595 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..ad240494ea 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 interface,grant table, evtchn or xenstore */

missing a whitespace


> +    uint32_t dom0less_feature;

Given that we only really need 2 bits today, and given that uint8_t and
uint16_t are free but uint32_t increases the size of the struct, could
we just use uint16_t dom0less_feature ?


Everything else looks good, these are just minor things.


>      /* GIC phandle */
>      uint32_t phandle_gic;
> -- 
> 2.25.1
>
Re: [PATCH v4 6/7] xen/arm: introduce new xen,enhanced property value
Posted by Rahul Singh 3 years, 5 months ago 
Hi Stefano,

> On 6 Sep 2022, at 11:12 pm, Stefano Stabellini <sstabellini@kernel.org> wrote:
> 
> On Tue, 6 Sep 2022, Rahul Singh wrote:
>> Introduce a new "xen,enhanced" dom0less property value "no-xenstore" to
>> disable xenstore interface for dom0less guests.
>> 
>> Signed-off-by: Rahul Singh <rahul.singh@arm.com>
>> ---
>> Changes in v4:
>> - Implement defines for dom0less features
>> Changes in v3:
>> - new patch in this version
>> ---
>> 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..1b0dca1454 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
>> +    Xen PV interfaces, including grant-table will be enabled but xenstore
>> +    will be disabled for the VM.
> 
> Please use "" for consistency:
> 
>    - "no-xenstore"
> 

Ack. 
> 
>>     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 707e247f6a..0b164ef595 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..ad240494ea 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 interface,grant table, evtchn or xenstore */
> 
> missing a whitespace

Ack. 
> 
> 
>> +    uint32_t dom0less_feature;
> 
> Given that we only really need 2 bits today, and given that uint8_t and
> uint16_t are free but uint32_t increases the size of the struct, could
> we just use uint16_t dom0less_feature ?

Yes, I will change to uint16_t in next version.

Regards,
Rahul

Patchew 2.1-devel-b67e4c2

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