From: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx> Sent: Monday, August 5, 2024 8:24 AM
>
> 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.
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.
Michael
