Re: [RFC PATCH 1/2] sys-hypervisor: /sys/hypervisor/type for Hyper-V

[Nuno Das Neves]

On 7/29/2019 3:54 PM, Nuno Das Neves wrote:
> *From:*Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
> *Sent:* Friday, 26 July 2019 5:43 PM
> *To:* Nuno Das Neves <Nuno.Das@xxxxxxxxxxxxx>; Nuno Das Neves <Nuno.Das@xxxxxxxxxxxxx>; gregkh@xxxxxxxxxxxxxxxxxxx <gregkh@xxxxxxxxxxxxxxxxxxx>; Sasha Levin <Alexander.Levin@xxxxxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>; Michael Kelley <mikelley@xxxxxxxxxxxxx>
> *Cc:* linux-kernel@xxxxxxxxxxxxxxx <linux-kernel@xxxxxxxxxxxxxxx>
> *Subject:* Re: [RFC PATCH 1/2] sys-hypervisor: /sys/hypervisor/type for Hyper-V
>  
> I am not sure about this. 
> The existing tools like lscpu just use CPUID. What is does this addition add?
> 
The main motivation is to replicate functionality available on Xen.

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> *From:* Nuno Das Neves <nudasnev@xxxxxxxxxxxxx>
> *Sent:* Friday, July 26, 2019 4:17 PM
> *To:* Nuno Das Neves <Nuno.Das@xxxxxxxxxxxxx>; gregkh@xxxxxxxxxxxxxxxxxxx <gregkh@xxxxxxxxxxxxxxxxxxx>; Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>; Sasha Levin <Alexander.Levin@xxxxxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>; Michael Kelley <mikelley@xxxxxxxxxxxxx>
> *Cc:* linux-kernel@xxxxxxxxxxxxxxx <linux-kernel@xxxxxxxxxxxxxxx>
> *Subject:* [RFC PATCH 1/2] sys-hypervisor: /sys/hypervisor/type for Hyper-V
>  
> Populate /sys/hypervisor with entries for Hyper-V.
> This patch adds /sys/hypervisor/type which contains "Hyper-V".
> 
> Signed-off-by: Nuno Das Neves <nudasnev@xxxxxxxxxxxxx>
> ---
>  .../ABI/stable/sysfs-hypervisor-hyperv        |  7 ++++
>  drivers/hv/Kconfig                            | 10 +++++
>  drivers/hv/Makefile                           |  7 ++--
>  drivers/hv/sys-hypervisor.c                   | 41 +++++++++++++++++++
>  4 files changed, 62 insertions(+), 3 deletions(-)
>  create mode 100644 Documentation/ABI/stable/sysfs-hypervisor-hyperv
>  create mode 100644 drivers/hv/sys-hypervisor.c
> 
> diff --git a/Documentation/ABI/stable/sysfs-hypervisor-hyperv b/Documentation/ABI/stable/sysfs-hypervisor-hyperv
> new file mode 100644
> index 000000000000..58380ea81315
> --- /dev/null
> +++ b/Documentation/ABI/stable/sysfs-hypervisor-hyperv
> @@ -0,0 +1,7 @@
> +What:          /sys/hypervisor/type
> +Date:          July 2019
> +KernelVersion: 5.2.1
> +Contact:       linux-hyperv@xxxxxxxxxxxxxxx
> +Description:   If running under Hyper-V:
> +               Type of hypervisor:
> +               "Hyper-V": Hyper-V hypervisor
> diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
> index 1c1a2514d6f3..e693adf0b77f 100644
> --- a/drivers/hv/Kconfig
> +++ b/drivers/hv/Kconfig
> @@ -25,4 +25,14 @@ config HYPERV_BALLOON
>          help
>            Select this option to enable Hyper-V Balloon driver.
>  
> +config HYPERV_SYS_HYPERVISOR
> +       bool "Create Hyper-V entries under /sys/hypervisor"
> +       depends on HYPERV && SYSFS
> +       select SYS_HYPERVISOR
> +       default y
> +       help
> +         Create Hyper-V entries under /sys/hypervisor (e.g., type). When running
> +         native or on another hypervisor, /sys/hypervisor may still be
> +         present, but it will have no Hyper-V entries.
> +
>  endmenu
> diff --git a/drivers/hv/Makefile b/drivers/hv/Makefile
> index a1eec7177c2d..87f569659555 100644
> --- a/drivers/hv/Makefile
> +++ b/drivers/hv/Makefile
> @@ -1,7 +1,8 @@
>  # SPDX-License-Identifier: GPL-2.0
> -obj-$(CONFIG_HYPERV)           += hv_vmbus.o
> -obj-$(CONFIG_HYPERV_UTILS)     += hv_utils.o
> -obj-$(CONFIG_HYPERV_BALLOON)   += hv_balloon.o
> +obj-$(CONFIG_HYPERV)                   += hv_vmbus.o
> +obj-$(CONFIG_HYPERV_UTILS)             += hv_utils.o
> +obj-$(CONFIG_HYPERV_BALLOON)           += hv_balloon.o
> +obj-$(CONFIG_HYPERV_SYS_HYPERVISOR)    += sys-hypervisor.o
>  
>  CFLAGS_hv_trace.o = -I$(src)
>  CFLAGS_hv_balloon.o = -I$(src)
> diff --git a/drivers/hv/sys-hypervisor.c b/drivers/hv/sys-hypervisor.c
> new file mode 100644
> index 000000000000..eb3d2a6502c4
> --- /dev/null
> +++ b/drivers/hv/sys-hypervisor.c
> @@ -0,0 +1,41 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Copyright (C) 2019, Microsoft, Inc.
> + *
> + * Authored by: Nuno Das Neves <nudasnev@xxxxxxxxxxxxx>
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/kobject.h>
> +#include <linux/err.h>
> +
> +#include <asm/hypervisor.h>
> +
> +static ssize_t type_show(struct kobject *obj,
> +                       struct kobj_attribute *attr,
> +                       char *buf)
> +{
> +       return sprintf(buf, "Hyper-V\n");
> +}
> +
> +static struct kobj_attribute type_attr = __ATTR_RO(type);
> +
> +static int __init hyperv_sysfs_type_init(void)
> +{
> +       return sysfs_create_file(hypervisor_kobj, &type_attr.attr);
> +}
> +
> +static int __init hyper_sysfs_init(void)
> +{
> +       int ret;
> +
> +       if (!hypervisor_is_type(X86_HYPER_MS_HYPERV))
> +               return -ENODEV;
> +
> +       ret = hyperv_sysfs_type_init();
> +
> +       return ret;
> +}
> +device_initcall(hyper_sysfs_init);
> -- 
> 2.17.1
>