diff mbox series

[v2,2/6] drivers/hv: Enable VTL mode for arm64

Message ID 20240514224508.212318-3-romank@linux.microsoft.com (mailing list archive)
State Changes Requested
Delegated to: Bjorn Helgaas
Headers show
Series arm64/hyperv: Support Virtual Trust Level Boot | expand

Commit Message

Roman Kisel May 14, 2024, 10:43 p.m. UTC
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@linux.microsoft.com>
---
 drivers/hv/Kconfig | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Comments

Michael Kelley May 15, 2024, 1:37 p.m. UTC | #1
From: Roman Kisel <romank@linux.microsoft.com> Sent: Tuesday, May 14, 2024 3:44 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@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

These changes make it possible to build a normal VTL 0 Hyper-V
guest (i.e., CONFIG_HYPERV_VTL_MODE=n) if CONFIG_ACPI is
not set, which won't work.  While we can say "don't do that", it
would be better if the Kconfig dependencies expressed that
requirement.

A possible fix is to remove the "depends on HYPERV" from
HYPERV_VTL_MODE.  Then for HYPERV, make
the "depends on ACPI" be conditional on !HYPERV_VTL_MODE
(for both ARM64 and X86).

I think we originally had "depends on HYPERV" in
HYPERV_VTL_MODE because there was a VTL-related function
in a non-Hyper-V code path, and we wanted to prevent that code
from running in non-Hyper-V environments.  But in practice, that
turned out not to work well because occasionally people would
do an "all config" build where both CONFIG_HYPERV and
CONFIG_HYPERV_VTL_MODE were set, and it would panic during
boot in their non-Hyper-V environment.  Such people were not
happy. :-(  So Saurabh made a relatively simple change (see commit
14058f72cf13e) that got the VTL code out of that non-Hyper-V code
path.  With that change, it shouldn't matter if someone sets
CONFIG_HYPERV_VTL_MODE=y in a build where
CONFIG_HYPERV=n.

At least that's my theory. :-)  Someone would need to check
it carefully.

Michael
Roman Kisel May 15, 2024, 6:04 p.m. UTC | #2
On 5/15/2024 6:37 AM, Michael Kelley wrote:
> From: Roman Kisel <romank@linux.microsoft.com> Sent: Tuesday, May 14, 2024 3:44 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@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
> 
> These changes make it possible to build a normal VTL 0 Hyper-V
> guest (i.e., CONFIG_HYPERV_VTL_MODE=n) if CONFIG_ACPI is
> not set, which won't work.  While we can say "don't do that", it
> would be better if the Kconfig dependencies expressed that
> requirement.
> 
> A possible fix is to remove the "depends on HYPERV" from
> HYPERV_VTL_MODE.  Then for HYPERV, make
> the "depends on ACPI" be conditional on !HYPERV_VTL_MODE
> (for both ARM64 and X86).
> 
> I think we originally had "depends on HYPERV" in
> HYPERV_VTL_MODE because there was a VTL-related function
> in a non-Hyper-V code path, and we wanted to prevent that code
> from running in non-Hyper-V environments.  But in practice, that
> turned out not to work well because occasionally people would
> do an "all config" build where both CONFIG_HYPERV and
> CONFIG_HYPERV_VTL_MODE were set, and it would panic during
> boot in their non-Hyper-V environment.  Such people were not
> happy. :-(  So Saurabh made a relatively simple change (see commit
> 14058f72cf13e) that got the VTL code out of that non-Hyper-V code
> path.  With that change, it shouldn't matter if someone sets
> CONFIG_HYPERV_VTL_MODE=y in a build where
> CONFIG_HYPERV=n.
> 
> At least that's my theory. :-)  Someone would need to check
> it carefully.
I'll explore that, appreciate sharing the context!

> 
> Michael
diff mbox series

Patch

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.