[PATCH v2 1/2] KVM: Start populating /sys/hypervisor with KVM entries

Filippo Sironi
2019-05-14T15:18:02Z

Start populating /sys/hypervisor with KVM entries when we're running on
KVM. This is to replicate functionality that's available when we're
running on Xen.

Start with /sys/hypervisor/uuid, which users prefer over
/sys/devices/virtual/dmi/id/product_uuid as a way to recognize a virtual
machine, since it's also available when running on Xen HVM and on Xen PV
and, on top of that doesn't require root privileges by default.
Let's create arch-specific hooks so that different architectures can
provide different implementations.

Signed-off-by: Filippo Sironi <sironi@amazon.de>
---
v2:
* move the retrieval of the VM UUID out of uuid_show and into
kvm_para_get_uuid, which is a weak function that can be overwritten

drivers/Kconfig | 2 ++
drivers/Makefile | 2 ++
drivers/kvm/Kconfig | 14 ++++++++++++++
drivers/kvm/Makefile | 1 +
drivers/kvm/sys-hypervisor.c | 30 ++++++++++++++++++++++++++++++
5 files changed, 49 insertions(+)
create mode 100644 drivers/kvm/Kconfig
create mode 100644 drivers/kvm/Makefile
create mode 100644 drivers/kvm/sys-hypervisor.c

diff --git a/drivers/Kconfig b/drivers/Kconfig
index 45f9decb9848..90eb835fe951 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -146,6 +146,8 @@ source "drivers/hv/Kconfig"

source "drivers/xen/Kconfig"

+source "drivers/kvm/Kconfig"
+
source "drivers/staging/Kconfig"

source "drivers/platform/Kconfig"
diff --git a/drivers/Makefile b/drivers/Makefile
index c61cde554340..79cc92a3f6bf 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -44,6 +44,8 @@ obj-y += soc/
obj-$(CONFIG_VIRTIO) += virtio/
obj-$(CONFIG_XEN) += xen/

+obj-$(CONFIG_KVM_GUEST) += kvm/
+
# regulators early, since some subsystems rely on them to initialize
obj-$(CONFIG_REGULATOR) += regulator/

diff --git a/drivers/kvm/Kconfig b/drivers/kvm/Kconfig
new file mode 100644
index 000000000000..3fc041df7c11
--- /dev/null
+++ b/drivers/kvm/Kconfig
@@ -0,0 +1,14 @@
+menu "KVM driver support"
+ depends on KVM_GUEST
+
+config KVM_SYS_HYPERVISOR
+ bool "Create KVM entries under /sys/hypervisor"
+ depends on SYSFS
+ select SYS_HYPERVISOR
+ default y
+ help
+ Create KVM entries under /sys/hypervisor (e.g., uuid). When running
+ native or on another hypervisor, /sys/hypervisor may still be
+ present, but it will have no KVM entries.
+
+endmenu
diff --git a/drivers/kvm/Makefile b/drivers/kvm/Makefile
new file mode 100644
index 000000000000..73a43fc994b9
--- /dev/null
+++ b/drivers/kvm/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_KVM_SYS_HYPERVISOR) += sys-hypervisor.o
diff --git a/drivers/kvm/sys-hypervisor.c b/drivers/kvm/sys-hypervisor.c
new file mode 100644
index 000000000000..43b1d1a09807
--- /dev/null
+++ b/drivers/kvm/sys-hypervisor.c
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <asm/kvm_para.h>
+
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
+
+__weak const char *kvm_para_get_uuid(void)
+{
+ return NULL;
+}
+
+static ssize_t uuid_show(struct kobject *obj,
+ struct kobj_attribute *attr,
+ char *buf)
+{
+ const char *uuid = kvm_para_get_uuid();
+ return sprintf(buf, "%s\n", uuid);
+}
+
+static struct kobj_attribute uuid = __ATTR_RO(uuid);
+
+static int __init uuid_init(void)
+{
+ if (!kvm_para_available())
+ return 0;
+ return sysfs_create_file(hypervisor_kobj, &uuid.attr);
+}
+
+device_initcall(uuid_init);
--
2.7.4