Re: [PATCH v3 06/12] virt: gunyah: Add sysfs nodes

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

On 12/08/2022 00:41, Elliot Berman wrote:
> 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@quicinc.com>
> ---
>   .../ABI/testing/sysfs-hypervisor-gunyah       | 23 +++++
>   MAINTAINERS                                   |  1 +
>   drivers/virt/Makefile                         |  1 +
>   drivers/virt/gunyah/Makefile                  |  2 +
>   drivers/virt/gunyah/sysfs.c                   | 87 +++++++++++++++++++
>   5 files changed, 114 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..219465783a9e
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-hypervisor-gunyah
> @@ -0,0 +1,23 @@
> +What:		/sys/hypervisor/type
> +Date:		August 2022
> +KernelVersion:	6.0
> +Contact:	linux-arm-msm@vger.kernel.org
> +Description:	If running under Gunyah:
> +		Type of hypervisor:
> +		"gunyah": Gunyah hypervisor

Note, you do not need the 'type'. You already have it in form of 
/sys/hypervisor/gunyah dir. If the VM is running under another type of 
hypervisor, there will be a different directory for hypervisor files.

> +
> +What:		/sys/hypervisor/gunyah/api
> +Date:		August 2022
> +KernelVersion:	6.0
> +Contact:	linux-arm-msm@vger.kernel.org
> +Description:	If running under Gunyah:
> +		The Gunyah API version.

Please provide examples here.

> +
> +What:		/sys/hypervisor/gunyah/variant
> +Date:		August 2022
> +KernelVersion:	6.0
> +Contact:	linux-arm-msm@vger.kernel.org
> +Description:	If running under Gunyah:
> +		The Gunyah variant (build) version.
> +		The open source build of Gunyah will report "81".
> +		The Qualcomm build of Gunyah will report "72".

Are these numbers fixed in stone? What if some other random company adds 
another variant of the Gunyah? What if the open source build is updated 
at some point?

> diff --git a/MAINTAINERS b/MAINTAINERS
> index f5d5ebb62701..c774bbcdb348 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8739,6 +8739,7 @@ M:	Elliot Berman <quic_eberman@quicinc.com>
>   M:	Murali Nalajala <quic_mnalajal@quicinc.com>
>   L:	linux-arm-msm@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..5cd759f60122 100644
> --- a/drivers/virt/Makefile
> +++ b/drivers/virt/Makefile
> @@ -9,5 +9,6 @@ obj-y				+= vboxguest/
>   
>   obj-$(CONFIG_NITRO_ENCLAVES)	+= nitro_enclaves/
>   obj-$(CONFIG_ACRN_HSM)		+= acrn/
> +obj-$(CONFIG_GUNYAH)		+= gunyah/
>   obj-$(CONFIG_EFI_SECRET)	+= coco/efi_secret/
>   obj-$(CONFIG_SEV_GUEST)		+= coco/sev-guest/
> diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
> new file mode 100644
> index 000000000000..e15f16c17142
> --- /dev/null
> +++ b/drivers/virt/gunyah/Makefile
> @@ -0,0 +1,2 @@
> +gunyah-y += sysfs.o
> +obj-$(CONFIG_GUNYAH) += gunyah.o
> diff --git a/drivers/virt/gunyah/sysfs.c b/drivers/virt/gunyah/sysfs.c
> new file mode 100644
> index 000000000000..9de700fdbfcb
> --- /dev/null
> +++ b/drivers/virt/gunyah/sysfs.c
> @@ -0,0 +1,87 @@
> +// 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 type_show(struct kobject *kobj, struct kobj_attribute *attr, char *buffer)
> +{
> +	return sysfs_emit(buffer, "gunyah\n");
> +}
> +static struct kobj_attribute type_attr = __ATTR_RO(type);
> +
> +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)
> +{
> +	int ret;
> +	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));
> +
> +	ret = sysfs_create_file(hypervisor_kobj, &type_attr.attr);
> +	if (ret)
> +		return ret;
> +
> +	ret = sysfs_create_group(hypervisor_kobj, &gunyah_group);
> +	if (ret)
> +		sysfs_remove_file(hypervisor_kobj, &type_attr.attr);
> +
> +	return ret;
> +}
> +module_init(gunyah_init);
> +
> +static void __exit gunyah_exit(void)
> +{
> +	sysfs_remove_group(hypervisor_kobj, &gunyah_group);
> +	sysfs_remove_file(hypervisor_kobj, &type_attr.attr);
> +}
> +module_exit(gunyah_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Gunyah Hypervisor Driver");

-- 
With best wishes
Dmitry