Re: [PATCH] vgacon: Fall back to the dummy console if mapping VGA memory fails

[Helge Deller <deller@gmx.de>]

On 11/12/26 09:47, Magnus Lindholm wrote:
> Hi Matt,
> 
> On Thu, Nov 12, 2026 at 1:30 AM Matt Turner <mattst88@gmail.com> wrote:
>>
>> On Alpha, setup_arch() registers vgacon whenever CONFIG_VGA_CONSOLE is
>> enabled. On Marvel (EV7) systems whose SRM console is serial, no VGA
>> hose is set, so marvel_ioremap() finds no hose for 0xb8000 and returns
>> NULL. vgacon_startup() then probes video memory through that NULL
>> pointer and oopses in console_init():
>>
>>    Unable to handle kernel paging request at virtual address 0000000000000000
>>    pc is at vgacon_startup+0x174/0x910
>>
>> VGA_MAP_MEM() is ioremap() on Alpha and powerpc and can fail. Treat
>> failure like a failed probe and fall back to the dummy console. If a
>> VGA card is present, locate_and_init_vga() still switches to vgacon
>> once PCI is up.
>>
>> Cc: stable@vger.kernel.org
>> Assisted-by: Claude:claude-opus-5-5
>> Signed-off-by: Matt Turner <mattst88@gmail.com>
>> ---
>>   drivers/video/console/vgacon.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
>> index e7e6750f1f87..09f7c376b468 100644
>> --- a/drivers/video/console/vgacon.c
>> +++ b/drivers/video/console/vgacon.c
>> @@ -324,6 +324,8 @@ static const char *vgacon_startup(void)
>>          }
>>
>>          vga_vram_base = VGA_MAP_MEM(vga_vram_base, vga_vram_size);
>> +       if (!vga_vram_base)
>> +               goto no_vga;
>>          vga_vram_end = vga_vram_base + vga_vram_size;
>>
>>          /*
>>
> ....
> 
> Reviewed-by: Magnus Lindholm <linmag7@gmail.com>
> Tested-by: Magnus Lindholm <linmag7@gmail.com>
applied to fbdev git tree.

Thanks!
Helge