RE: [PATCH v3 5/5] x86/Kconfig: Add HYPERV_VTL_MODE

[Michael Kelley (LINUX)]

From: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx> Sent: Monday, March 20, 2023 3:04 AM
> 
> Add HYPERV_VTL_MODE Kconfig flag for VTL mode.
> 
> Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
> ---
>  arch/x86/Kconfig         | 24 ++++++++++++++++++++++++
>  arch/x86/hyperv/Makefile |  1 +
>  2 files changed, 25 insertions(+)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 453f462f6c9c..c3faaaea1e31 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -782,6 +782,30 @@ menuconfig HYPERVISOR_GUEST
> 
>  if HYPERVISOR_GUEST
> 
> +config HYPERV_VTL_MODE
> +	bool "Enable Linux to boot in VTL context"
> +	depends on X86_64 && HYPERV
> +	default n
> +	help
> +	  Virtual Secure Mode (VSM) is a set of hypervisor capabilities and
> +	  enlightenments offered to host and guest partitions which enables
> +	  the creation and management of new security boundaries within
> +	  operating system software.
> +
> +	  VSM achieves and maintains isolation through Virtual Trust Levels
> +	  (VTLs). Virtual Trust Levels are hierarchical, with higher levels
> +	  being more privileged than lower levels. VTL0 is the least privileged
> +	  level, and currently only other level supported is VTL2.
> +
> +	  Select this option to build a Linux kernel to run at a VTL other than
> +	  the normal VTL0, which currently is only VTL2.  This option
> +	  initializes the x86 platform for VTL2, and adds the ability to boot
> +	  secondary CPUs directly into 64-bit context as required for VTLs other
> +	  than 0.  A kernel built with this option must run at VTL2, and will
> +	  not run as a normal guest.
> +
> +	  If unsure, say N
> +

Is there a reason for putting this in arch/x86/Kconfig instead of in
drivers/hv/Kconfig under the "Microsoft Hyper-V guest support"
menu with the other Hyper-V settings?  It seems like grouping
this with the other Hyper-V settings would make it easier to find,
unless there's some reason that doesn't work.

Michael

>  config PARAVIRT
>  	bool "Enable paravirtualization code"
>  	depends on HAVE_STATIC_CALL
> diff --git a/arch/x86/hyperv/Makefile b/arch/x86/hyperv/Makefile
> index 5d2de10809ae..3a1548054b48 100644
> --- a/arch/x86/hyperv/Makefile
> +++ b/arch/x86/hyperv/Makefile
> @@ -1,6 +1,7 @@
>  # SPDX-License-Identifier: GPL-2.0-only
>  obj-y			:= hv_init.o mmu.o nested.o irqdomain.o ivm.o
>  obj-$(CONFIG_X86_64)	+= hv_apic.o hv_proc.o
> +obj-$(CONFIG_HYPERV_VTL_MODE)	+= hv_vtl.o
> 
>  ifdef CONFIG_X86_64
>  obj-$(CONFIG_PARAVIRT_SPINLOCKS)	+= hv_spinlock.o
> --
> 2.34.1