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 <rom...@linux.microsoft.com> 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 <rom...@linux.microsoft.com>
---
  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!

Saurabh,

I could try out the idea you're offering if you folks are fine with that. Or, we could let this be for the time being and grapple with that in a separate patch series :)

- Saurabh

--
Thank you,
Roman


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