> >
> > On 8/4/2024 9:05 PM, Saurabh Singh Sengar wrote:
> > > On Mon, Aug 05, 2024 at 03:01:58AM +0000, Michael Kelley wrote:
> > >> From: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx> Sent: Friday, July 26, 2024 3:59
> > PM
> > >>>
> > >>> Kconfig dependencies for arm64 guests on Hyper-V require that be ACPI enabled,
> > >>> and limit VTL mode to x86/x64. To enable VTL mode on arm64 as well, update the
> > >>> dependencies. Since VTL mode requires DeviceTree instead of ACPI, don't require
> > >>> arm64 guests on Hyper-V to have ACPI.
> > >>>
> > >>> Signed-off-by: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx>
> > >>> ---
> > >>> drivers/hv/Kconfig | 6 +++---
> > >>> 1 file changed, 3 insertions(+), 3 deletions(-)
> > >>>
> > >>> diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
> > >>> index 862c47b191af..a5cd1365e248 100644
> > >>> --- a/drivers/hv/Kconfig
> > >>> +++ b/drivers/hv/Kconfig
> > >>> @@ -5,7 +5,7 @@ menu "Microsoft Hyper-V guest support"
> > >>> config HYPERV
> > >>> tristate "Microsoft Hyper-V client drivers"
> > >>> depends on (X86 && X86_LOCAL_APIC && HYPERVISOR_GUEST) \
> > >>> - || (ACPI && ARM64 && !CPU_BIG_ENDIAN)
> > >>> + || (ARM64 && !CPU_BIG_ENDIAN)
> > >>> select PARAVIRT
> > >>> select X86_HV_CALLBACK_VECTOR if X86
> > >>> select OF_EARLY_FLATTREE if OF
> > >>> @@ -15,7 +15,7 @@ config HYPERV
> > >>>
> > >>> config HYPERV_VTL_MODE
> > >>> bool "Enable Linux to boot in VTL context"
> > >>> - depends on X86_64 && HYPERV
> > >>> + depends on HYPERV
> > >>> depends on SMP
> > >>> default n
> > >>> help
> > >>> @@ -31,7 +31,7 @@ config HYPERV_VTL_MODE
> > >>>
> > >>> 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
> > >>> + initializes the kernel to run in 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.
> > >>> --
> > >>> 2.34.1
> > >>>
> > >>
> > >> In v2 of this patch, I suggested [1] making a couple additional minor changes
> > >> so that kernels built *without* HYPER_VTL_MODE would still require
> > >> ACPI. Did that suggestion not work out? If that's the case, I'm curious
> > >> about what goes wrong.
> > >
> > > Hi Michael/Roman,
> > > I was considering making HYPERV_VTL_MODE depend on CONFIG_OF. That should
> > address
> > > above concern as well. Do you see any potential issue with it.
> > >
> > Michael,
> >
> > I ran into a pretty gnarly recursive dependencies which in all fairness
> > might stem from not being fluent enough in the Kconfig language. Any
> > help of how to approach implementing your idea would be greatly appreciated!
> >
>
> This is what I had in mind:
>
> --- a/drivers/hv/Kconfig
> +++ b/drivers/hv/Kconfig
> @@ -5,7 +5,8 @@ menu "Microsoft Hyper-V guest support"
> config HYPERV
> tristate "Microsoft Hyper-V client drivers"
> depends on (X86 && X86_LOCAL_APIC && HYPERVISOR_GUEST) \
> - || (ACPI && ARM64 && !CPU_BIG_ENDIAN)
> + || (ARM64 && !CPU_BIG_ENDIAN)
> + depends on (ACPI || HYPERV_VTL_MODE)
> select PARAVIRT
> select X86_HV_CALLBACK_VECTOR if X86
> select OF_EARLY_FLATTREE if OF
> @@ -15,7 +16,7 @@ config HYPERV
>
> config HYPERV_VTL_MODE
> bool "Enable Linux to boot in VTL context"
> - depends on X86_64 && HYPERV
> + depends on X86_64
> depends on SMP
> default n
> help
>
> HYPERV_VTL_MODE can now be selected independently of HYPERV.
> The existing code should be such that even if someone is building a
> random config and gets HYPERV_VTL_MODE without HYPERV, the
> kernel will build and run in a non-Hyper-V environment and isn't
> broken somehow.
>
> For HYPERV to be selected, either ACPI must already be selected, or
> HYPERV_VTL_MODE must already be selected. So "normal" kernels are
> still enforced to require ACPI. But if building with HYPERV_VTL_MODE,
> then ACPI is optional.
>
Thanks a ton! Let me try this out for the (arch; VTL) build matrix :)
> Saurabh's idea of adding "depends on OF" to HYPERV_VTL_MODE
> should also work with these changes.
>
> I haven't fully tested the above with all the relevant combinations
> on both x86 and arm64, but I think the logic makes sense.
