[PATCH v2] vga: don't abort when adding a duplicate isa-vga device

[PATCH v2] vga: don't abort when adding a duplicate isa-vga device

[Jose R. Ziviani]

If users try to add an isa-vga device that was already registered,
still in command line, qemu will crash:

$ qemu-system-mips64el -M pica61 -device isa-vga
RAMBlock "vga.vram" already registered, abort!
Aborted (core dumped)

That particular board registers the device automaticaly, so it's
not obvious that a VGA device already exists. This patch changes
this behavior by displaying a message and exiting without crashing.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/44
Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
---
 hw/display/vga-isa.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/display/vga-isa.c b/hw/display/vga-isa.c
index 90851e730b..1fba33b22b 100644
--- a/hw/display/vga-isa.c
+++ b/hw/display/vga-isa.c
@@ -33,6 +33,7 @@
 #include "hw/loader.h"
 #include "hw/qdev-properties.h"
 #include "qom/object.h"
+#include "qapi/error.h"
 
 #define TYPE_ISA_VGA "isa-vga"
 OBJECT_DECLARE_SIMPLE_TYPE(ISAVGAState, ISA_VGA)
@@ -61,6 +62,15 @@ static void vga_isa_realizefn(DeviceState *dev, Error **errp)
     MemoryRegion *vga_io_memory;
     const MemoryRegionPortio *vga_ports, *vbe_ports;
 
+    /*
+     * make sure this device is not being added twice, if so
+     * exit without crashing qemu
+     */
+    if (qemu_ram_block_by_name("vga.vram")) {
+        error_setg(errp, "vga.vram is already registered");
+        return;
+    }
+
     s->global_vmstate = true;
     vga_common_init(s, OBJECT(dev));
     s->legacy_address_space = isa_address_space(isadev);
-- 
2.32.0

Re: [PATCH v2] vga: don't abort when adding a duplicate isa-vga device

[Philippe Mathieu-Daudé]

On 8/16/21 2:36 PM, Jose R. Ziviani wrote:
> If users try to add an isa-vga device that was already registered,
> still in command line, qemu will crash:
> 
> $ qemu-system-mips64el -M pica61 -device isa-vga
> RAMBlock "vga.vram" already registered, abort!
> Aborted (core dumped)
> 
> That particular board registers the device automaticaly, so it's
> not obvious that a VGA device already exists. This patch changes
> this behavior by displaying a message and exiting without crashing.
> 
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/44
> Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
> ---
>  hw/display/vga-isa.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/hw/display/vga-isa.c b/hw/display/vga-isa.c
> index 90851e730b..1fba33b22b 100644
> --- a/hw/display/vga-isa.c
> +++ b/hw/display/vga-isa.c
> @@ -33,6 +33,7 @@
>  #include "hw/loader.h"
>  #include "hw/qdev-properties.h"
>  #include "qom/object.h"
> +#include "qapi/error.h"
>  
>  #define TYPE_ISA_VGA "isa-vga"
>  OBJECT_DECLARE_SIMPLE_TYPE(ISAVGAState, ISA_VGA)
> @@ -61,6 +62,15 @@ static void vga_isa_realizefn(DeviceState *dev, Error **errp)
>      MemoryRegion *vga_io_memory;
>      const MemoryRegionPortio *vga_ports, *vbe_ports;
>  
> +    /*
> +     * make sure this device is not being added twice, if so
> +     * exit without crashing qemu
> +     */
> +    if (qemu_ram_block_by_name("vga.vram")) {
> +        error_setg(errp, "vga.vram is already registered");

Maybe "'isa-vga' device already registered" is easier to understand?
(vga.vram is about the device model internal).

Otherwise:
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> +        return;
> +    }
> +
>      s->global_vmstate = true;
>      vga_common_init(s, OBJECT(dev));
>      s->legacy_address_space = isa_address_space(isadev);
> 

Re: [PATCH v2] vga: don't abort when adding a duplicate isa-vga device

[Jose Ricardo Ziviani]

Hello Philippe!

On 16/08/2021 10:01, Philippe Mathieu-Daudé wrote:
> On 8/16/21 2:36 PM, Jose R. Ziviani wrote:
>> If users try to add an isa-vga device that was already registered,
>> still in command line, qemu will crash:
>>
>> $ qemu-system-mips64el -M pica61 -device isa-vga
>> RAMBlock "vga.vram" already registered, abort!
>> Aborted (core dumped)
>>
>> That particular board registers the device automaticaly, so it's
>> not obvious that a VGA device already exists. This patch changes
>> this behavior by displaying a message and exiting without crashing.
>>
>> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/44
>> Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
>> ---
>>   hw/display/vga-isa.c | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/hw/display/vga-isa.c b/hw/display/vga-isa.c
>> index 90851e730b..1fba33b22b 100644
>> --- a/hw/display/vga-isa.c
>> +++ b/hw/display/vga-isa.c
>> @@ -33,6 +33,7 @@
>>   #include "hw/loader.h"
>>   #include "hw/qdev-properties.h"
>>   #include "qom/object.h"
>> +#include "qapi/error.h"
>>   
>>   #define TYPE_ISA_VGA "isa-vga"
>>   OBJECT_DECLARE_SIMPLE_TYPE(ISAVGAState, ISA_VGA)
>> @@ -61,6 +62,15 @@ static void vga_isa_realizefn(DeviceState *dev, Error **errp)
>>       MemoryRegion *vga_io_memory;
>>       const MemoryRegionPortio *vga_ports, *vbe_ports;
>>   
>> +    /*
>> +     * make sure this device is not being added twice, if so
>> +     * exit without crashing qemu
>> +     */
>> +    if (qemu_ram_block_by_name("vga.vram")) {
>> +        error_setg(errp, "vga.vram is already registered");
> Maybe "'isa-vga' device already registered" is easier to understand?
> (vga.vram is about the device model internal).

Much better message, sending a v3 with this improvement.

Thank you!


>
> Otherwise:
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>
>> +        return;
>> +    }
>> +
>>       s->global_vmstate = true;
>>       vga_common_init(s, OBJECT(dev));
>>       s->legacy_address_space = isa_address_space(isadev);
>>