[PATCH 1/1] Drivers: hv: Select CONFIG_SYSFB only if EFI is enabled

[PATCH 1/1] Drivers: hv: Select CONFIG_SYSFB only if EFI is enabled

[mhkelley58]

From: Michael Kelley <mhklinux@outlook.com>

Commit 96959283a58d ("Drivers: hv: Always select CONFIG_SYSFB
for Hyper-V guests") selects CONFIG_SYSFB for Hyper-V guests
so that screen_info is available to the VMBus driver to get
the location of the framebuffer in Generation 2 VMs. However,
if CONFIG_HYPERV is enabled but CONFIG_EFI is not, a kernel
link error results in ARM64 builds because screen_info is
provided by the EFI firmware interface. While configuring
an ARM64 Hyper-V guest without EFI isn't useful since EFI is
required to boot, the configuration is still possible and
the link error should be prevented.

Fix this by making the selection of CONFIG_SYSFB conditional
on CONFIG_EFI being defined. For Generation 1 VMs on x86/x64,
which don't use EFI, the additional condition is OK because
such VMs get the framebuffer information via a mechanism
that doesn't use screen_info.

Fixes: 96959283a58d ("Drivers: hv: Always select CONFIG_SYSFB for Hyper-V guests")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Closes: https://lore.kernel.org/linux-hyperv/20250610091810.2638058-1-arnd@kernel.org/
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202506080820.1wmkQufc-lkp@intel.com/
Signed-off-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/hv/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 1cd188b73b74..57623ca7f350 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -9,7 +9,7 @@ config HYPERV
 	select PARAVIRT
 	select X86_HV_CALLBACK_VECTOR if X86
 	select OF_EARLY_FLATTREE if OF
-	select SYSFB if !HYPERV_VTL_MODE
+	select SYSFB if EFI && !HYPERV_VTL_MODE
 	help
 	  Select this option to run Linux as a Hyper-V client operating
 	  system.
-- 
2.25.1

Re: [PATCH 1/1] Drivers: hv: Select CONFIG_SYSFB only if EFI is enabled

[kernel test robot]

Hi,

Thanks for your patch.

FYI: kernel test robot notices the stable kernel rule is not satisfied.

The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html#option-1

Rule: add the tag "Cc: stable@vger.kernel.org" in the sign-off area to have the patch automatically included in the stable tree.
Subject: [PATCH 1/1] Drivers: hv: Select CONFIG_SYSFB only if EFI is enabled
Link: https://lore.kernel.org/stable/20250613230059.380483-1-mhklinux%40outlook.com

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

RE: [PATCH 1/1] Drivers: hv: Select CONFIG_SYSFB only if EFI is enabled

[Michael Kelley]

From: mhkelley58@gmail.com <mhkelley58@gmail.com> Sent: Friday, June 13, 2025 4:01 PM
> 
> Commit 96959283a58d ("Drivers: hv: Always select CONFIG_SYSFB
> for Hyper-V guests") selects CONFIG_SYSFB for Hyper-V guests
> so that screen_info is available to the VMBus driver to get
> the location of the framebuffer in Generation 2 VMs. However,
> if CONFIG_HYPERV is enabled but CONFIG_EFI is not, a kernel
> link error results in ARM64 builds because screen_info is
> provided by the EFI firmware interface. While configuring
> an ARM64 Hyper-V guest without EFI isn't useful since EFI is
> required to boot, the configuration is still possible and
> the link error should be prevented.
> 
> Fix this by making the selection of CONFIG_SYSFB conditional
> on CONFIG_EFI being defined. For Generation 1 VMs on x86/x64,
> which don't use EFI, the additional condition is OK because
> such VMs get the framebuffer information via a mechanism
> that doesn't use screen_info.
> 
> Fixes: 96959283a58d ("Drivers: hv: Always select CONFIG_SYSFB for Hyper-V guests")
> Reported-by: Arnd Bergmann <arnd@arndb.de>
> Closes: https://lore.kernel.org/linux-hyperv/20250610091810.2638058-1-arnd@kernel.org/

Arnd -- Can you give a "Reviewed-by:" or "Acked-by:" for this fix?  It
needs to get into linux-next and then into Linus' tree before we
get too late in the 6.16 release cycle.

Michael

> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202506080820.1wmkQufc-lkp@intel.com/
> Signed-off-by: Michael Kelley <mhklinux@outlook.com>
> ---
>  drivers/hv/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
> index 1cd188b73b74..57623ca7f350 100644
> --- a/drivers/hv/Kconfig
> +++ b/drivers/hv/Kconfig
> @@ -9,7 +9,7 @@ config HYPERV
>  	select PARAVIRT
>  	select X86_HV_CALLBACK_VECTOR if X86
>  	select OF_EARLY_FLATTREE if OF
> -	select SYSFB if !HYPERV_VTL_MODE
> +	select SYSFB if EFI && !HYPERV_VTL_MODE
>  	help
>  	  Select this option to run Linux as a Hyper-V client operating
>  	  system.
> --
> 2.25.1
> 

Re: [PATCH 1/1] Drivers: hv: Select CONFIG_SYSFB only if EFI is enabled

[Roman Kisel]

On 6/13/2025 4:00 PM, mhkelley58@gmail.com wrote:
> From: Michael Kelley <mhklinux@outlook.com>
> 
> Commit 96959283a58d ("Drivers: hv: Always select CONFIG_SYSFB
> for Hyper-V guests") selects CONFIG_SYSFB for Hyper-V guests
> so that screen_info is available to the VMBus driver to get
> the location of the framebuffer in Generation 2 VMs. However,
> if CONFIG_HYPERV is enabled but CONFIG_EFI is not, a kernel
> link error results in ARM64 builds because screen_info is
> provided by the EFI firmware interface. While configuring
> an ARM64 Hyper-V guest without EFI isn't useful since EFI is
> required to boot, the configuration is still possible and
> the link error should be prevented.
> 
> Fix this by making the selection of CONFIG_SYSFB conditional
> on CONFIG_EFI being defined. For Generation 1 VMs on x86/x64,
> which don't use EFI, the additional condition is OK because
> such VMs get the framebuffer information via a mechanism
> that doesn't use screen_info.
> 

[...]

LGTM.
Reviewed-by: Roman Kisel <romank@linux.microsoft.com>

-- 
Thank you,
Roman

Re: [PATCH 1/1] Drivers: hv: Select CONFIG_SYSFB only if EFI is enabled

[Wei Liu]

On Fri, Jun 13, 2025 at 04:00:59PM -0700, mhkelley58@gmail.com wrote:
> From: Michael Kelley <mhklinux@outlook.com>
> 
> Commit 96959283a58d ("Drivers: hv: Always select CONFIG_SYSFB
> for Hyper-V guests") selects CONFIG_SYSFB for Hyper-V guests
> so that screen_info is available to the VMBus driver to get
> the location of the framebuffer in Generation 2 VMs. However,
> if CONFIG_HYPERV is enabled but CONFIG_EFI is not, a kernel
> link error results in ARM64 builds because screen_info is
> provided by the EFI firmware interface. While configuring
> an ARM64 Hyper-V guest without EFI isn't useful since EFI is
> required to boot, the configuration is still possible and
> the link error should be prevented.
> 
> Fix this by making the selection of CONFIG_SYSFB conditional
> on CONFIG_EFI being defined. For Generation 1 VMs on x86/x64,
> which don't use EFI, the additional condition is OK because
> such VMs get the framebuffer information via a mechanism
> that doesn't use screen_info.
> 
> Fixes: 96959283a58d ("Drivers: hv: Always select CONFIG_SYSFB for Hyper-V guests")
> Reported-by: Arnd Bergmann <arnd@arndb.de>
> Closes: https://lore.kernel.org/linux-hyperv/20250610091810.2638058-1-arnd@kernel.org/
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202506080820.1wmkQufc-lkp@intel.com/
> Signed-off-by: Michael Kelley <mhklinux@outlook.com>

Applied to hyperv-fixes. Thanks!