linux-kernel - Re: [Xen-devel] [PATCH 2/2] xen: add sysfs node for guest type

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Date:   Mon, 22 May 2017 11:23:25 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Juergen Gross <jgross@...e.com>
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        boris.ostrovsky@...cle.com
Subject: Re: [Xen-devel] [PATCH 2/2] xen: add sysfs node for guest type

On Mon, May 22, 2017 at 10:57:00AM +0200, Juergen Gross wrote:
> Currently there is no reliable user interface inside a Xen guest to
> determine its type (e.g. HVM, PV or PVH). Instead of letting user mode
> try to determine this by various rather hacky mechanisms (parsing of
> boot messages before they are gone, trying to make use of known subtle
> differences in behavior of some instructions), add a sysfs node
> /sys/hypervisor/guest_type to explicitly deliver this information as
> it is known to the kernel.
> 
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
>  Documentation/ABI/testing/sysfs-hypervisor | 13 +++++++++++++

You forgot to CC Greg KH who is the maintainer of that file.
>  arch/arm/xen/enlighten.c                   |  3 +++
>  arch/x86/xen/enlighten.c                   |  3 +++
>  arch/x86/xen/enlighten_hvm.c               |  6 ++++--
>  arch/x86/xen/enlighten_pv.c                |  1 +
>  drivers/xen/sys-hypervisor.c               | 17 +++++++++++++++++
>  include/xen/xen.h                          |  2 ++
>  7 files changed, 43 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-hypervisor b/Documentation/ABI/testing/sysfs-hypervisor
> index 443196f0aa1c..06850f74ebd4 100644
> --- a/Documentation/ABI/testing/sysfs-hypervisor
> +++ b/Documentation/ABI/testing/sysfs-hypervisor
> @@ -19,6 +19,19 @@ Contact:	xen-devel@...ts.xenproject.org
>  Description:
>  		Compiler which was used to build the Xen hypervisor
>  
> +What:		/sys/hypervisor/guest_type
> +Date:		May 2017
> +KernelVersion:	4.12
> +Contact:	xen-devel@...ts.xenproject.org
> +Description:
> +		Type of guest:
> +		"native": standard guest type on arm
> +		"HVM": fully virtualized guest (x86)
> +		"PV": paravirtualized guest (x86)
> +		"PVH": fully virtualized guest without legacy emulation (x86)
> +		"PVHVM": fully virtualized guest using paravirtualized
> +			interfaces (e.g. interrupts, timers) (x86)

What about KVM? Shouldn't that also be here?

And what should be there if say you boot without Xen, what is the correct value
on x86 (above 'native' says arm)?