[PATCH v4 0/4] xen: add xen sysfs nodes

[PATCH v4 0/4] xen: add xen sysfs nodes

[Juergen Gross]

In order to be able to determine the Xen guest type from within the
guest as a user there is currently no stable interface available.

Add a sysfs node for that purpose as the guest type information is
available for the kernel.

While doing this document all the other Xen related sysfs nodes.

Add another node to show the Xen hypervisor buildid in order to make
hypervisor live patching easier.

Juergen Gross (4):
  doc,xen: document hypervisor sysfs nodes for xen
  xen: add sysfs node for guest type
  xen: sync include/xen/interface/version.h
  xen: add sysfs node for hypervisor build id

 Documentation/ABI/stable/sysfs-hypervisor-xen      | 119 +++++++++++++++++++++
 .../{sysfs-hypervisor-pmu => sysfs-hypervisor-xen} |  24 ++++-
 MAINTAINERS                                        |   2 +
 drivers/xen/sys-hypervisor.c                       |  59 ++++++++++
 include/xen/interface/version.h                    |  15 +++
 5 files changed, 217 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/ABI/stable/sysfs-hypervisor-xen
 rename Documentation/ABI/testing/{sysfs-hypervisor-pmu => sysfs-hypervisor-xen} (54%)

-- 
2.12.3

[PATCH v4 1/4] doc,xen: document hypervisor sysfs nodes for xen

[Juergen Gross]

Today only a few sysfs nodes under /sys/hypervisor/ are documented
for Xen in Documentation/ABI/testing/sysfs-hypervisor-pmu.

Add the remaining Xen sysfs nodes under /sys/hypervisor/ in a new
file Documentation/ABI/stable/sysfs-hypervisor-xen and add the Xen
specific sysfs docs to the MAINTAINERS file.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
V4:
  - s/full/fully/ (Boris Ostrovsky)
V3:
  - added hint for hidden values where appropriate (Andrew Cooper)

V2:
  - rename file to Documentation/ABI/stable/sysfs-hypervisor-xen in
    order to reflect Xen dependency
  - leave pmu entries in old file under testing (Boris Ostrovsky)
---
 Documentation/ABI/stable/sysfs-hypervisor-xen | 119 ++++++++++++++++++++++++++
 MAINTAINERS                                   |   2 +
 2 files changed, 121 insertions(+)
 create mode 100644 Documentation/ABI/stable/sysfs-hypervisor-xen

diff --git a/Documentation/ABI/stable/sysfs-hypervisor-xen b/Documentation/ABI/stable/sysfs-hypervisor-xen
new file mode 100644
index 000000000000..3cf5cdfcd9a8
--- /dev/null
+++ b/Documentation/ABI/stable/sysfs-hypervisor-xen
@@ -0,0 +1,119 @@
+What:		/sys/hypervisor/compilation/compile_date
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Contains the build time stamp of the Xen hypervisor
+		Might return "<denied>" in case of special security settings
+		in the hypervisor.
+
+What:		/sys/hypervisor/compilation/compiled_by
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Contains information who built the Xen hypervisor
+		Might return "<denied>" in case of special security settings
+		in the hypervisor.
+
+What:		/sys/hypervisor/compilation/compiler
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Compiler which was used to build the Xen hypervisor
+		Might return "<denied>" in case of special security settings
+		in the hypervisor.
+
+What:		/sys/hypervisor/properties/capabilities
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Space separated list of supported guest system types. Each type
+		is in the format: <class>-<major>.<minor>-<arch>
+		With:
+			<class>: "xen" -- x86: paravirtualized, arm: standard
+				 "hvm" -- x86 only: fully virtualized
+			<major>: major guest interface version
+			<minor>: minor guest interface version
+			<arch>:  architecture, e.g.:
+				 "x86_32": 32 bit x86 guest without PAE
+				 "x86_32p": 32 bit x86 guest with PAE
+				 "x86_64": 64 bit x86 guest
+				 "armv7l": 32 bit arm guest
+				 "aarch64": 64 bit arm guest
+
+What:		/sys/hypervisor/properties/changeset
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Changeset of the hypervisor (git commit)
+		Might return "<denied>" in case of special security settings
+		in the hypervisor.
+
+What:		/sys/hypervisor/properties/features
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Features the Xen hypervisor supports for the guest as defined
+		in include/xen/interface/features.h printed as a hex value.
+
+What:		/sys/hypervisor/properties/pagesize
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Default page size of the hypervisor printed as a hex value.
+		Might return "0" in case of special security settings
+		in the hypervisor.
+
+What:		/sys/hypervisor/properties/virtual_start
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Virtual address of the hypervisor as a hex value.
+
+What:		/sys/hypervisor/type
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Type of hypervisor:
+		"xen": Xen hypervisor
+
+What:		/sys/hypervisor/uuid
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		UUID of the guest as known to the Xen hypervisor.
+
+What:		/sys/hypervisor/version/extra
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		The Xen version is in the format <major>.<minor><extra>
+		This is the <extra> part of it.
+		Might return "<denied>" in case of special security settings
+		in the hypervisor.
+
+What:		/sys/hypervisor/version/major
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		The Xen version is in the format <major>.<minor><extra>
+		This is the <major> part of it.
+
+What:		/sys/hypervisor/version/minor
+Date:		March 2009
+KernelVersion:	2.6.30
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		The Xen version is in the format <major>.<minor><extra>
+		This is the <minor> part of it.
diff --git a/MAINTAINERS b/MAINTAINERS
index 09b5ab6a8a5c..68c31aebb79c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13982,6 +13982,8 @@ F:	drivers/xen/
 F:	arch/x86/include/asm/xen/
 F:	include/xen/
 F:	include/uapi/xen/
+F:	Documentation/ABI/stable/sysfs-hypervisor-xen
+F:	Documentation/ABI/testing/sysfs-hypervisor-pmu
 
 XEN HYPERVISOR ARM
 M:	Stefano Stabellini <sstabellini@kernel.org>
-- 
2.12.3

[PATCH v4 2/4] xen: add sysfs node for guest type

[Juergen Gross]

Currently there is no reliable user interface inside a Xen guest to
determine its type (e.g. HVM, PV or PVH). Instead of letting user mode
try to determine this by various rather hacky mechanisms (parsing of
boot messages before they are gone, trying to make use of known subtle
differences in behavior of some instructions), add a sysfs node
/sys/hypervisor/guest_type to explicitly deliver this information as
it is known to the kernel.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V4:
  - use xen_domain_type instead of introducing xen_guest_type
    (Boris Ostrovsky)
V2:
  - remove PVHVM guest type (Andrew Cooper)
  - move description to Documentation/ABI/testing/sysfs-hypervisor-xen
    (Boris Ostrovsky)
  - make xen_guest_type const char * (Jan Beulich)
  - modify standard ARM guest type to "Xen"
---
 .../{sysfs-hypervisor-pmu => sysfs-hypervisor-xen} | 15 +++++++++--
 MAINTAINERS                                        |  2 +-
 drivers/xen/sys-hypervisor.c                       | 31 ++++++++++++++++++++++
 3 files changed, 45 insertions(+), 3 deletions(-)
 rename Documentation/ABI/testing/{sysfs-hypervisor-pmu => sysfs-hypervisor-xen} (67%)

diff --git a/Documentation/ABI/testing/sysfs-hypervisor-pmu b/Documentation/ABI/testing/sysfs-hypervisor-xen
similarity index 67%
rename from Documentation/ABI/testing/sysfs-hypervisor-pmu
rename to Documentation/ABI/testing/sysfs-hypervisor-xen
index 224faa105e18..c0edb3fdd6eb 100644
--- a/Documentation/ABI/testing/sysfs-hypervisor-pmu
+++ b/Documentation/ABI/testing/sysfs-hypervisor-xen
@@ -1,8 +1,19 @@
+What:		/sys/hypervisor/guest_type
+Date:		May 2017
+KernelVersion:	4.13
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Type of guest:
+		"Xen": standard guest type on arm
+		"HVM": fully virtualized guest (x86)
+		"PV": paravirtualized guest (x86)
+		"PVH": fully virtualized guest without legacy emulation (x86)
+
 What:		/sys/hypervisor/pmu/pmu_mode
 Date:		August 2015
 KernelVersion:	4.3
 Contact:	Boris Ostrovsky <boris.ostrovsky@oracle.com>
-Description:
+Description:	If running under Xen:
 		Describes mode that Xen's performance-monitoring unit (PMU)
 		uses. Accepted values are
 			"off"  -- PMU is disabled
@@ -17,7 +28,7 @@ What:           /sys/hypervisor/pmu/pmu_features
 Date:           August 2015
 KernelVersion:  4.3
 Contact:        Boris Ostrovsky <boris.ostrovsky@oracle.com>
-Description:
+Description:	If running under Xen:
 		Describes Xen PMU features (as an integer). A set bit indicates
 		that the corresponding feature is enabled. See
 		include/xen/interface/xenpmu.h for available features
diff --git a/MAINTAINERS b/MAINTAINERS
index 68c31aebb79c..5630439429e6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13983,7 +13983,7 @@ F:	arch/x86/include/asm/xen/
 F:	include/xen/
 F:	include/uapi/xen/
 F:	Documentation/ABI/stable/sysfs-hypervisor-xen
-F:	Documentation/ABI/testing/sysfs-hypervisor-pmu
+F:	Documentation/ABI/testing/sysfs-hypervisor-xen
 
 XEN HYPERVISOR ARM
 M:	Stefano Stabellini <sstabellini@kernel.org>
diff --git a/drivers/xen/sys-hypervisor.c b/drivers/xen/sys-hypervisor.c
index 84106f9c456c..10400917e8e8 100644
--- a/drivers/xen/sys-hypervisor.c
+++ b/drivers/xen/sys-hypervisor.c
@@ -50,6 +50,32 @@ static int __init xen_sysfs_type_init(void)
 	return sysfs_create_file(hypervisor_kobj, &type_attr.attr);
 }
 
+static ssize_t guest_type_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	const char *type = "???";
+
+	switch (xen_domain_type) {
+	case XEN_NATIVE:
+		/* ARM only. */
+		type = "Xen";
+		break;
+	case XEN_PV_DOMAIN:
+		type = "PV";
+		break;
+	case XEN_HVM_DOMAIN:
+		type = xen_pvh_domain() ? "PVH" : "HVM";
+		break;
+	}
+	return sprintf(buffer, "%s\n", type);
+}
+
+HYPERVISOR_ATTR_RO(guest_type);
+
+static int __init xen_sysfs_guest_type_init(void)
+{
+	return sysfs_create_file(hypervisor_kobj, &guest_type_attr.attr);
+}
+
 /* xen version attributes */
 static ssize_t major_show(struct hyp_sysfs_attr *attr, char *buffer)
 {
@@ -471,6 +497,9 @@ static int __init hyper_sysfs_init(void)
 	ret = xen_sysfs_type_init();
 	if (ret)
 		goto out;
+	ret = xen_sysfs_guest_type_init();
+	if (ret)
+		goto guest_type_out;
 	ret = xen_sysfs_version_init();
 	if (ret)
 		goto version_out;
@@ -502,6 +531,8 @@ static int __init hyper_sysfs_init(void)
 comp_out:
 	sysfs_remove_group(hypervisor_kobj, &version_group);
 version_out:
+	sysfs_remove_file(hypervisor_kobj, &guest_type_attr.attr);
+guest_type_out:
 	sysfs_remove_file(hypervisor_kobj, &type_attr.attr);
 out:
 	return ret;
-- 
2.12.3

Re: [PATCH v4 2/4] xen: add sysfs node for guest type

[Boris Ostrovsky]

> --- a/Documentation/ABI/testing/sysfs-hypervisor-pmu
> +++ b/Documentation/ABI/testing/sysfs-hypervisor-xen
> @@ -1,8 +1,19 @@
> +What:		/sys/hypervisor/guest_type
> +Date:		May 2017
> +KernelVersion:	4.13
> +Contact:	xen-devel@lists.xenproject.org
> +Description:	If running under Xen:
> +		Type of guest:
> +		"Xen": standard guest type on arm
> +		"HVM": fully virtualized guest (x86)
> +		"PV": paravirtualized guest (x86)
> +		"PVH": fully virtualized guest without legacy emulation (x86)
> +
>  



>  
> +static ssize_t guest_type_show(struct hyp_sysfs_attr *attr, char *buffer)
> +{
> +	const char *type = "???";
> +
> +	switch (xen_domain_type) {
> +	case XEN_NATIVE:
> +		/* ARM only. */
> +		type = "Xen";
> +		break;
> +	case XEN_PV_DOMAIN:
> +		type = "PV";
> +		break;
> +	case XEN_HVM_DOMAIN:
> +		type = xen_pvh_domain() ? "PVH" : "HVM";
> +		break;
> +	}

I think we should return -EINVAL for unknown type. Or document "???" in
the ABI document.


-boris

> +	return sprintf(buffer, "%s\n", type);
> +}
>

Re: [PATCH v4 2/4] xen: add sysfs node for guest type

[Juergen Gross]

[-- Attachment #1: Type: text/plain, Size: 1114 bytes --]

On 14/06/17 19:43, Boris Ostrovsky wrote:
> 
>> --- a/Documentation/ABI/testing/sysfs-hypervisor-pmu
>> +++ b/Documentation/ABI/testing/sysfs-hypervisor-xen
>> @@ -1,8 +1,19 @@
>> +What:		/sys/hypervisor/guest_type
>> +Date:		May 2017
>> +KernelVersion:	4.13
>> +Contact:	xen-devel@lists.xenproject.org
>> +Description:	If running under Xen:
>> +		Type of guest:
>> +		"Xen": standard guest type on arm
>> +		"HVM": fully virtualized guest (x86)
>> +		"PV": paravirtualized guest (x86)
>> +		"PVH": fully virtualized guest without legacy emulation (x86)
>> +
>>  
> 
> 
> 
>>  
>> +static ssize_t guest_type_show(struct hyp_sysfs_attr *attr, char *buffer)
>> +{
>> +	const char *type = "???";
>> +
>> +	switch (xen_domain_type) {
>> +	case XEN_NATIVE:
>> +		/* ARM only. */
>> +		type = "Xen";
>> +		break;
>> +	case XEN_PV_DOMAIN:
>> +		type = "PV";
>> +		break;
>> +	case XEN_HVM_DOMAIN:
>> +		type = xen_pvh_domain() ? "PVH" : "HVM";
>> +		break;
>> +	}
> 
> I think we should return -EINVAL for unknown type. Or document "???" in
> the ABI document.

Hmm, okay. Are you fine with the attached patch?


Juergen

[-- Attachment #2: v5-0001-xen-add-sysfs-node-for-guest-type.patch --]
[-- Type: text/x-patch, Size: 4802 bytes --]

>From b8661036e7465eab99f988cec3fe37e35536eb40 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Wed, 14 Jun 2017 17:12:45 +0200
Subject: [PATCH v5] xen: add sysfs node for guest type

Currently there is no reliable user interface inside a Xen guest to
determine its type (e.g. HVM, PV or PVH). Instead of letting user mode
try to determine this by various rather hacky mechanisms (parsing of
boot messages before they are gone, trying to make use of known subtle
differences in behavior of some instructions), add a sysfs node
/sys/hypervisor/guest_type to explicitly deliver this information as
it is known to the kernel.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V4:
  - use xen_domain_type instead of introducing xen_guest_type
    (Boris Ostrovsky)
V2:
  - remove PVHVM guest type (Andrew Cooper)
  - move description to Documentation/ABI/testing/sysfs-hypervisor-xen
    (Boris Ostrovsky)
  - make xen_guest_type const char * (Jan Beulich)
  - modify standard ARM guest type to "Xen"
---
 .../{sysfs-hypervisor-pmu => sysfs-hypervisor-xen} | 15 ++++++++--
 MAINTAINERS                                        |  2 +-
 drivers/xen/sys-hypervisor.c                       | 34 ++++++++++++++++++++++
 3 files changed, 48 insertions(+), 3 deletions(-)
 rename Documentation/ABI/testing/{sysfs-hypervisor-pmu => sysfs-hypervisor-xen} (67%)

diff --git a/Documentation/ABI/testing/sysfs-hypervisor-pmu b/Documentation/ABI/testing/sysfs-hypervisor-xen
similarity index 67%
rename from Documentation/ABI/testing/sysfs-hypervisor-pmu
rename to Documentation/ABI/testing/sysfs-hypervisor-xen
index 224faa105e18..c0edb3fdd6eb 100644
--- a/Documentation/ABI/testing/sysfs-hypervisor-pmu
+++ b/Documentation/ABI/testing/sysfs-hypervisor-xen
@@ -1,8 +1,19 @@
+What:		/sys/hypervisor/guest_type
+Date:		May 2017
+KernelVersion:	4.13
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Type of guest:
+		"Xen": standard guest type on arm
+		"HVM": fully virtualized guest (x86)
+		"PV": paravirtualized guest (x86)
+		"PVH": fully virtualized guest without legacy emulation (x86)
+
 What:		/sys/hypervisor/pmu/pmu_mode
 Date:		August 2015
 KernelVersion:	4.3
 Contact:	Boris Ostrovsky <boris.ostrovsky@oracle.com>
-Description:
+Description:	If running under Xen:
 		Describes mode that Xen's performance-monitoring unit (PMU)
 		uses. Accepted values are
 			"off"  -- PMU is disabled
@@ -17,7 +28,7 @@ What:           /sys/hypervisor/pmu/pmu_features
 Date:           August 2015
 KernelVersion:  4.3
 Contact:        Boris Ostrovsky <boris.ostrovsky@oracle.com>
-Description:
+Description:	If running under Xen:
 		Describes Xen PMU features (as an integer). A set bit indicates
 		that the corresponding feature is enabled. See
 		include/xen/interface/xenpmu.h for available features
diff --git a/MAINTAINERS b/MAINTAINERS
index 68c31aebb79c..5630439429e6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13983,7 +13983,7 @@ F:	arch/x86/include/asm/xen/
 F:	include/xen/
 F:	include/uapi/xen/
 F:	Documentation/ABI/stable/sysfs-hypervisor-xen
-F:	Documentation/ABI/testing/sysfs-hypervisor-pmu
+F:	Documentation/ABI/testing/sysfs-hypervisor-xen
 
 XEN HYPERVISOR ARM
 M:	Stefano Stabellini <sstabellini@kernel.org>
diff --git a/drivers/xen/sys-hypervisor.c b/drivers/xen/sys-hypervisor.c
index 84106f9c456c..2f78f84a31e9 100644
--- a/drivers/xen/sys-hypervisor.c
+++ b/drivers/xen/sys-hypervisor.c
@@ -50,6 +50,35 @@ static int __init xen_sysfs_type_init(void)
 	return sysfs_create_file(hypervisor_kobj, &type_attr.attr);
 }
 
+static ssize_t guest_type_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	const char *type;
+
+	switch (xen_domain_type) {
+	case XEN_NATIVE:
+		/* ARM only. */
+		type = "Xen";
+		break;
+	case XEN_PV_DOMAIN:
+		type = "PV";
+		break;
+	case XEN_HVM_DOMAIN:
+		type = xen_pvh_domain() ? "PVH" : "HVM";
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return sprintf(buffer, "%s\n", type);
+}
+
+HYPERVISOR_ATTR_RO(guest_type);
+
+static int __init xen_sysfs_guest_type_init(void)
+{
+	return sysfs_create_file(hypervisor_kobj, &guest_type_attr.attr);
+}
+
 /* xen version attributes */
 static ssize_t major_show(struct hyp_sysfs_attr *attr, char *buffer)
 {
@@ -471,6 +500,9 @@ static int __init hyper_sysfs_init(void)
 	ret = xen_sysfs_type_init();
 	if (ret)
 		goto out;
+	ret = xen_sysfs_guest_type_init();
+	if (ret)
+		goto guest_type_out;
 	ret = xen_sysfs_version_init();
 	if (ret)
 		goto version_out;
@@ -502,6 +534,8 @@ static int __init hyper_sysfs_init(void)
 comp_out:
 	sysfs_remove_group(hypervisor_kobj, &version_group);
 version_out:
+	sysfs_remove_file(hypervisor_kobj, &guest_type_attr.attr);
+guest_type_out:
 	sysfs_remove_file(hypervisor_kobj, &type_attr.attr);
 out:
 	return ret;
-- 
2.12.3

Re: [PATCH v4 2/4] xen: add sysfs node for guest type

[Boris Ostrovsky]

> Hmm, okay. Are you fine with the attached patch?


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

[PATCH v4 3/4] xen: sync include/xen/interface/version.h

[Juergen Gross]

Sync include/xen/interface/version.h with the Xen source.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
 include/xen/interface/version.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/xen/interface/version.h b/include/xen/interface/version.h
index 7ff6498679a3..145f12f9ecec 100644
--- a/include/xen/interface/version.h
+++ b/include/xen/interface/version.h
@@ -63,4 +63,19 @@ struct xen_feature_info {
 /* arg == xen_domain_handle_t. */
 #define XENVER_guest_handle 8
 
+#define XENVER_commandline 9
+struct xen_commandline {
+	char buf[1024];
+};
+
+/*
+ * Return value is the number of bytes written, or XEN_Exx on error.
+ * Calling with empty parameter returns the size of build_id.
+ */
+#define XENVER_build_id 10
+struct xen_build_id {
+	uint32_t	len; /* IN: size of buf[]. */
+	unsigned char	buf[];
+};
+
 #endif /* __XEN_PUBLIC_VERSION_H__ */
-- 
2.12.3

[PATCH v4 4/4] xen: add sysfs node for hypervisor build id

[Juergen Gross]

For support of Xen hypervisor live patching the hypervisor build id is
needed. Add a node /sys/hypervisor/properties/buildid containing the
information.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V4:
  - send correct patch
---
 Documentation/ABI/testing/sysfs-hypervisor-xen | 11 +++++++++-
 drivers/xen/sys-hypervisor.c                   | 28 ++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-hypervisor-xen b/Documentation/ABI/testing/sysfs-hypervisor-xen
index c0edb3fdd6eb..53b7b2ea7515 100644
--- a/Documentation/ABI/testing/sysfs-hypervisor-xen
+++ b/Documentation/ABI/testing/sysfs-hypervisor-xen
@@ -1,5 +1,5 @@
 What:		/sys/hypervisor/guest_type
-Date:		May 2017
+Date:		June 2017
 KernelVersion:	4.13
 Contact:	xen-devel@lists.xenproject.org
 Description:	If running under Xen:
@@ -32,3 +32,12 @@ Description:	If running under Xen:
 		Describes Xen PMU features (as an integer). A set bit indicates
 		that the corresponding feature is enabled. See
 		include/xen/interface/xenpmu.h for available features
+
+What:		/sys/hypervisor/properties/buildid
+Date:		June 2017
+KernelVersion:	4.13
+Contact:	xen-devel@lists.xenproject.org
+Description:	If running under Xen:
+		Build id of the hypervisor, needed for hypervisor live patching.
+		Might return "<denied>" in case of special security settings
+		in the hypervisor.
diff --git a/drivers/xen/sys-hypervisor.c b/drivers/xen/sys-hypervisor.c
index 10400917e8e8..f8eeed46fbc3 100644
--- a/drivers/xen/sys-hypervisor.c
+++ b/drivers/xen/sys-hypervisor.c
@@ -353,12 +353,40 @@ static ssize_t features_show(struct hyp_sysfs_attr *attr, char *buffer)
 
 HYPERVISOR_ATTR_RO(features);
 
+static ssize_t buildid_show(struct hyp_sysfs_attr *attr, char *buffer)
+{
+	ssize_t ret;
+	struct xen_build_id *buildid;
+
+	ret = HYPERVISOR_xen_version(XENVER_build_id, NULL);
+	if (ret < 0) {
+		if (ret == -EPERM)
+			ret = sprintf(buffer, "<denied>");
+		return ret;
+	}
+
+	buildid = kmalloc(sizeof(*buildid) + ret, GFP_KERNEL);
+	if (!buildid)
+		return -ENOMEM;
+
+	buildid->len = ret;
+	ret = HYPERVISOR_xen_version(XENVER_build_id, buildid);
+	if (ret > 0)
+		ret = sprintf(buffer, "%s", buildid->buf);
+	kfree(buildid);
+
+	return ret;
+}
+
+HYPERVISOR_ATTR_RO(buildid);
+
 static struct attribute *xen_properties_attrs[] = {
 	&capabilities_attr.attr,
 	&changeset_attr.attr,
 	&virtual_start_attr.attr,
 	&pagesize_attr.attr,
 	&features_attr.attr,
+	&buildid_attr.attr,
 	NULL
 };
 
-- 
2.12.3

Re: [PATCH v4 4/4] xen: add sysfs node for hypervisor build id

[Boris Ostrovsky]

On 06/14/2017 01:23 PM, Juergen Gross wrote:
> For support of Xen hypervisor live patching the hypervisor build id is
> needed. Add a node /sys/hypervisor/properties/buildid containing the
> information.
>
> Signed-off-by: Juergen Gross <jgross@suse.com>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>