[PATCH v4 06/14] virt: gunyah: Add sysfs nodes

[Elliot Berman]

Add /sys/hypervisor support when detecting that Linux is running in a
Gunyah environment. Export the version of Gunyah which is reported via
the hyp_identify hypercall.

Signed-off-by: Elliot Berman <quic_eberman at quicinc.com>
---
 .../ABI/testing/sysfs-hypervisor-gunyah       | 15 ++++
 MAINTAINERS                                   |  1 +
 drivers/virt/Makefile                         |  1 +
 drivers/virt/gunyah/Makefile                  |  2 +
 drivers/virt/gunyah/sysfs.c                   | 71 +++++++++++++++++++
 5 files changed, 90 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-hypervisor-gunyah
 create mode 100644 drivers/virt/gunyah/Makefile
 create mode 100644 drivers/virt/gunyah/sysfs.c

diff --git a/Documentation/ABI/testing/sysfs-hypervisor-gunyah b/Documentation/ABI/testing/sysfs-hypervisor-gunyah
new file mode 100644
index 000000000000..7d74e74e9edd
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-hypervisor-gunyah
@@ -0,0 +1,15 @@
+What:		/sys/hypervisor/gunyah/api
+Date:		October 2022
+KernelVersion:	6.1
+Contact:	linux-arm-msm at vger.kernel.org
+Description:	If running under Gunyah:
+		The Gunyah API version.
+
+What:		/sys/hypervisor/gunyah/variant
+Date:		October 2022
+KernelVersion:	6.1
+Contact:	linux-arm-msm at vger.kernel.org
+Description:	If running under Gunyah:
+		Reports the build variant of Gunyah:
+		The open source build of Gunyah will report "81".
+		The Qualcomm build of Gunyah will report "72".
diff --git a/MAINTAINERS b/MAINTAINERS
index feafac12db35..a26e67ef36b4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8885,6 +8885,7 @@ M:	Elliot Berman <quic_eberman at quicinc.com>
 M:	Murali Nalajala <quic_mnalajal at quicinc.com>
 L:	linux-arm-msm at vger.kernel.org
 S:	Supported
+F:	Documentation/ABI/testing/sysfs-hypervisor-gunyah
 F:	Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
 F:	Documentation/virt/gunyah/
 F:	arch/arm64/gunyah/
diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
index 093674e05c40..10b87f934730 100644
--- a/drivers/virt/Makefile
+++ b/drivers/virt/Makefile
@@ -11,3 +11,4 @@ obj-$(CONFIG_NITRO_ENCLAVES)	+= nitro_enclaves/
 obj-$(CONFIG_ACRN_HSM)		+= acrn/
 obj-$(CONFIG_EFI_SECRET)	+= coco/efi_secret/
 obj-$(CONFIG_SEV_GUEST)		+= coco/sev-guest/
+obj-$(CONFIG_GUNYAH)		+= gunyah/
diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
new file mode 100644
index 000000000000..e15f16c17142
--- /dev/null
+++ b/drivers/virt/gunyah/Makefile
@@ -0,0 +1,2 @@
+gunyah-y += sysfs.o
+obj-$(CONFIG_GUNYAH) += gunyah.o
diff --git a/drivers/virt/gunyah/sysfs.c b/drivers/virt/gunyah/sysfs.c
new file mode 100644
index 000000000000..ec11510cbece
--- /dev/null
+++ b/drivers/virt/gunyah/sysfs.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#define pr_fmt(fmt) "gunyah: " fmt
+
+#include <linux/kobject.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/init.h>
+#include <asm-generic/gunyah.h>
+
+static struct gh_hypercall_hyp_identify_resp gunyah_api;
+
+static ssize_t api_show(struct kobject *kobj, struct kobj_attribute *attr, char *buffer)
+{
+	return sysfs_emit(buffer, "%d\n", (int)GH_API_INFO_API_VERSION(gunyah_api.api_info));
+}
+static struct kobj_attribute api_attr = __ATTR_RO(api);
+
+static ssize_t variant_show(struct kobject *kobj, struct kobj_attribute *attr, char *buffer)
+{
+	return sysfs_emit(buffer, "%d\n", (int)GH_API_INFO_VARIANT(gunyah_api.api_info));
+}
+static struct kobj_attribute variant_attr = __ATTR_RO(variant);
+
+static struct attribute *gunyah_attrs[] = {
+	&api_attr.attr,
+	&variant_attr.attr,
+	NULL
+};
+
+static const struct attribute_group gunyah_group = {
+	.name = "gunyah",
+	.attrs = gunyah_attrs,
+};
+
+static int __init gunyah_init(void)
+{
+	u32 uid[4];
+
+	gh_hypercall_get_uid(uid);
+
+	if (!(gh_uid_matches(GUNYAH, uid) || gh_uid_matches(QC_HYP, uid)))
+		return 0;
+
+	gh_hypercall_hyp_identify(&gunyah_api);
+
+	if (GH_API_INFO_API_VERSION(gunyah_api.api_info) != 1) {
+		pr_warn("Unrecognized gunyah version: %llu. Currently supported: 1\n",
+			GH_API_INFO_API_VERSION(gunyah_api.api_info));
+		return 0;
+	}
+
+	pr_notice("Running under Gunyah hypervisor %llx/v%lld\n",
+		  GH_API_INFO_VARIANT(gunyah_api.api_info),
+		  GH_API_INFO_API_VERSION(gunyah_api.api_info));
+
+	return sysfs_create_group(hypervisor_kobj, &gunyah_group);
+}
+module_init(gunyah_init);
+
+static void __exit gunyah_exit(void)
+{
+	sysfs_remove_group(hypervisor_kobj, &gunyah_group);
+}
+module_exit(gunyah_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Gunyah Hypervisor Driver");
-- 
2.25.1