linux-kernel - Re: [PATCH] KVM: Start populating /sys/hypervisor with KVM entries

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Date:   Tue, 9 Oct 2018 11:00:35 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Filippo Sironi <sironi@...zon.de>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: Start populating /sys/hypervisor with KVM entries

On Tue, Oct 09, 2018 at 11:54:39AM +0200, Filippo Sironi wrote:
> 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.
> 
> Let's 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.

Yeey! Thank you for doing this. It has been on my TODO but just never
got to it.

I think you also need to update the Documentation/../sysfs file.
> 
> Signed-off-by: Filippo Sironi <sironi@...zon.de>
> ---
>  drivers/Kconfig              |  2 ++
>  drivers/Makefile             |  2 ++
>  drivers/kvm/Kconfig          | 14 ++++++++++++++
>  drivers/kvm/Makefile         |  1 +
>  drivers/kvm/sys-hypervisor.c | 26 ++++++++++++++++++++++++++
>  5 files changed, 45 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 afc942c54814..597519c5f7c8 100644
> --- a/drivers/Kconfig
> +++ b/drivers/Kconfig
> @@ -135,6 +135,8 @@ 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 1056f9699192..727205e287fc 100644
> --- a/drivers/Makefile
> +++ b/drivers/Makefile
> @@ -47,6 +47,8 @@ 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..ef04ca65cf1a
> --- /dev/null
> +++ b/drivers/kvm/sys-hypervisor.c
> @@ -0,0 +1,26 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#include <asm/kvm_para.h>
> +
> +#include <linux/dmi.h>
> +#include <linux/kobject.h>
> +#include <linux/sysfs.h>
> +
> +static ssize_t uuid_show(struct kobject *obj,
> +			 struct kobj_attribute *attr,
> +			 char *buf)
> +{
> +	const char *uuid = dmi_get_system_info(DMI_PRODUCT_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
>