linux-kernel - Re: [PATCH] drivers/virt: vm_gen_counter: initial driver implementation

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Date:   Thu, 22 Feb 2018 18:49:00 +0200
From:   Gal Hammer <ghammer@...hat.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Or Idgar <idgar@...tualoco.com>, linux-kernel@...r.kernel.org,
        arnd@...db.de, Or Idgar <oridgar@...il.com>
Subject: Re: [PATCH] drivers/virt: vm_gen_counter: initial driver implementation

Hi,

On Thu, Feb 22, 2018 at 6:36 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Thu, Feb 22, 2018 at 06:20:38PM +0200, Or Idgar wrote:
>> From: Or Idgar <oridgar@...il.com>
>>
>> This patch is a driver which expose the Virtual Machine Generation ID
>> via sysfs. The ID is a UUID value used to differentiate between virtual
>> machines.
>>
>> The VM-Generation ID is a feature defined by Microsoft (paper:
>> http://go.microsoft.com/fwlink/?LinkId=260709) and supported by multiple
>> hypervisor vendors.
>>
>> Signed-off-by: Or Idgar <oridgar@...il.com>
>> ---
>>  Documentation/ABI/testing/sysfs-hypervisor |  13 +++
>>  drivers/misc/Kconfig                       |   6 ++
>>  drivers/misc/Makefile                      |   1 +
>>  drivers/misc/vmgenid.c                     | 141 +++++++++++++++++++++++++++++
>>  4 files changed, 161 insertions(+)
>>  create mode 100644 Documentation/ABI/testing/sysfs-hypervisor
>>  create mode 100644 drivers/misc/vmgenid.c
>>
>> diff --git a/Documentation/ABI/testing/sysfs-hypervisor b/Documentation/ABI/testing/sysfs-hypervisor
>> new file mode 100644
>> index 000000000000..2f9a7b8eab70
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-hypervisor
>> @@ -0,0 +1,13 @@
>> +What:                /sys/hypervisor/vm_gen_counter
>
> Shouldn't this go under the specific hypervisor you are running on?  Why
> in the "root" of /sys/hypervisor?

As far as I know, most of today's hypervisors support this feature, so
adding a subdirectory doesn't seem right. The guest user should be
able to access the UUID without a knowledge of the running host.

At the moment, the driver supports only QEMU, but we're planning to
enhance it once we'll have access to other vendor hypervisors.

>
>> +Date:                February 2018
>> +Contact:     Or Idgar <idgar@...tualoco.com>
>> +             Gal Hammer <ghammer@...hat.com>
>> +Description: Expose the virtual machine generation ID. The directory
>> +             contains two files: "generation_id" and "raw". Both files
>> +             represent the same information.
>> +
>> +             "generation_id" file is a UUID string
>> +             representation.
>> +
>> +             "raw" file is a 128-bit integer
>> +             representation (binary).
>> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
>> index 03605f8fc0dc..5a74802bdfb4 100644
>> --- a/drivers/misc/Kconfig
>> +++ b/drivers/misc/Kconfig
>> @@ -500,6 +500,12 @@ config MISC_RTSX
>>       tristate
>>       default MISC_RTSX_PCI || MISC_RTSX_USB
>>
>> +config VMGENID
>> +     tristate "Virtual Machine Generation ID driver"
>> +     help
>> +       This is a Virtual Machine Generation ID driver which provides
>> +       a virtual machine unique identifier.
>> +
>>  source "drivers/misc/c2port/Kconfig"
>>  source "drivers/misc/eeprom/Kconfig"
>>  source "drivers/misc/cb710/Kconfig"
>> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
>> index c3c8624f4d95..067aa666bb6a 100644
>> --- a/drivers/misc/Makefile
>> +++ b/drivers/misc/Makefile
>> @@ -57,6 +57,7 @@ obj-$(CONFIG_ASPEED_LPC_SNOOP)      += aspeed-lpc-snoop.o
>>  obj-$(CONFIG_PCI_ENDPOINT_TEST)      += pci_endpoint_test.o
>>  obj-$(CONFIG_OCXL)           += ocxl/
>>  obj-$(CONFIG_MISC_RTSX)              += cardreader/
>> +obj-$(CONFIG_VMGENID)                += vmgenid.o
>>
>>  lkdtm-$(CONFIG_LKDTM)                += lkdtm_core.o
>>  lkdtm-$(CONFIG_LKDTM)                += lkdtm_bugs.o
>> diff --git a/drivers/misc/vmgenid.c b/drivers/misc/vmgenid.c
>> new file mode 100644
>> index 000000000000..9d7f09f9e7bd
>> --- /dev/null
>> +++ b/drivers/misc/vmgenid.c
>> @@ -0,0 +1,141 @@
>> +/*
>> + * Virtual Machine Generation ID driver
>> + *
>> + * Copyright (C) 2018 Red Hat, Inc. All rights reserved.
>> + *   Authors:
>> + *     Or Idgar <oridgar@...il.com>
>> + *     Gal Hammer <ghammer@...hat.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>
> No SPDX line?  Please see the documentation for how to properly add this
> as the first line of any new file.

We'll give it another try.

> I want some hypervisor people to weigh in on this before I can take
> it...
>
> thanks,
>
> greg k-h

Thank you.

    Gal.