[PATCH 0/1] Correct Video Corruption for EFI Plus Bochs

[PATCH 0/1] Correct Video Corruption for EFI Plus Bochs

[Andrew Hamilton]

Disable building video_bochs for EFI x86 platforms. For EFI platforms
efi_gop or efi_uga should provide the video support. Currently,
in EFI platforms there is a risk that both the bochs devices is
present and the EFI video interface - which can cause unexpected
video corruption when a mix of the two interfaces are used. This
can happen when all_video is loaded for simplicity in a GRUB config.

There is some additional analysis from the Qemu team in this thread:
https://gitlab.com/qemu-project/qemu/-/issues/2562

This is an issue on some major distros such as Debian on EFI
when running under Qemu and potentially other scenarios.

There is some discussion on the Debian side in this thread:
https://salsa.debian.org/kernel-team/linux/-/merge_requests/1453

This relates to this discussion from grub-devel also:
https://lists.gnu.org/archive/html/grub-devel/2025-09/msg00244.html

Fixes: https://savannah.gnu.org/bugs/index.php?66200

Andrew Hamilton (1):
  build: Disable building video_bochs for EFI x86 platforms

 grub-core/Makefile.core.def | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

-- 
2.47.3


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[PATCH 1/1] build: Disable building video_bochs for EFI x86 platforms

[Andrew Hamilton]

Disable building video_bochs for EFI x86 platforms. For EFI platforms
efi_gop or efi_uga should provide the video support. Currently,
in EFI platforms there is a risk that both the bochs devices is
present and the EFI video interface - which can cause unexpected
video corruption when a mix of the two interfaces are used. This
can happen when all_video is loaded for simplicity in a GRUB config.

Fixes: https://savannah.gnu.org/bugs/index.php?66200

Signed-off-by: Andrew Hamilton <adhamilt@gmail.com>
---
 grub-core/Makefile.core.def | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
index 0fcf67f9d..0caaec9dd 100644
--- a/grub-core/Makefile.core.def
+++ b/grub-core/Makefile.core.def
@@ -2169,7 +2169,11 @@ module = {
 module = {
   name = video_bochs;
   x86 = video/bochs.c;
-  enable = x86;
+  enable = i386_pc;
+  enable = i386_qemu;
+  enable = i386_coreboot;
+  enable = i386_multiboot;
+  enable = i386_ieee1275;
 };
 
 module = {
-- 
2.47.3


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Re: [PATCH 0/1] Correct Video Corruption for EFI Plus Bochs

[Askar Safin via Grub-devel]

 ---- On Sun, 28 Sep 2025 18:29:48 +0400  Andrew Hamilton <adhamilt@gmail.com> wrote --- 
 > Disable building video_bochs for EFI x86 platforms. For EFI platforms
 > efi_gop or efi_uga should provide the video support. Currently,

Thank you! I tested your patch, and it indeed solves the issue.
But the problem still exists if I pass "-vga cirrus" to Qemu.
I. e. we need to disable video_cirrus, too.

So, please, disable ALL video drivers, except for efi_gop and efi_uga.

And this should apply to all UEFI architectures, not only to x86.
-- 
Askar Safin
https://types.pl/@safinaskar


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Re: [PATCH 0/1] Correct Video Corruption for EFI Plus Bochs

[Andrew Hamilton]

[-- Attachment #1.1: Type: text/plain, Size: 784 bytes --]

Thanks, I’ll send out a v2 this evening.

Sincerely,
Andrew

On Sun, Sep 28, 2025 at 11:43 PM Askar Safin <safinaskar@zohomail.com>
wrote:

>  ---- On Sun, 28 Sep 2025 18:29:48 +0400  Andrew Hamilton <
> adhamilt@gmail.com> wrote ---
>  > Disable building video_bochs for EFI x86 platforms. For EFI platforms
>  > efi_gop or efi_uga should provide the video support. Currently,
>
> Thank you! I tested your patch, and it indeed solves the issue.
> But the problem still exists if I pass "-vga cirrus" to Qemu.
> I. e. we need to disable video_cirrus, too.
>
> So, please, disable ALL video drivers, except for efi_gop and efi_uga.
>
> And this should apply to all UEFI architectures, not only to x86.
> --
> Askar Safin
> https://types.pl/@safinaskar
>
>

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Re: [PATCH 0/1] Correct Video Corruption for EFI Plus Bochs

[Ben Hutchings]

[-- Attachment #1.1: Type: text/plain, Size: 1046 bytes --]

On Mon, 2025-09-29 at 08:43 +0400, Askar Safin wrote:
>  ---- On Sun, 28 Sep 2025 18:29:48 +0400  Andrew Hamilton <adhamilt@gmail.com> wrote --- 
>  > Disable building video_bochs for EFI x86 platforms. For EFI platforms
>  > efi_gop or efi_uga should provide the video support. Currently,
> 
> Thank you! I tested your patch, and it indeed solves the issue.
> But the problem still exists if I pass "-vga cirrus" to Qemu.
> I. e. we need to disable video_cirrus, too.
> 
> So, please, disable ALL video drivers, except for efi_gop and efi_uga.

I support this request.

> And this should apply to all UEFI architectures, not only to x86.

I'm not sure about this, though.  On x86 it seems safe to assume that
the system firmware and discrete graphics cards have a UEFI graphics
driver and support GOP.  On other platforms, UEFI may be implemented by
U-Boot, where video support is optional.  So this could be a regression
for them.

Ben.

-- 
Ben Hutchings - Debian developer, member of kernel, installer and LTS
teams

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