linux-kernel - RE: [PATCH v3 2/7] Drivers: hv: Enable VTL mode for arm64

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Message-ID:
 <SN6PR02MB4157824AC8ECA000559F5160D4BE2@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Mon, 5 Aug 2024 03:01:58 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Roman Kisel <romank@...ux.microsoft.com>, "arnd@...db.de" <arnd@...db.de>,
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Subject: RE: [PATCH v3 2/7] Drivers: hv: Enable VTL mode for arm64

From: Roman Kisel <romank@...ux.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 <romank@...ux.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.

Michael

[1] https://lore.kernel.org/all/SN6PR02MB4157E15EFE263BBA3D8DFC51D4EC2@SN6PR02MB4157.namprd02.prod.outlook.com/