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

[Markus Armbruster]

Thomas Huth  writes:

> On 14/08/2021 01.36, 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 such device automaticaly, so it's
>> not obvious that a VGA device already exists. This patch changes
>> this behavior by displaying a message and ignoring that device,
>> starting qemu normally.
>> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/44
>> Signed-off-by: Jose R. Ziviani 
>> ---
>>   hw/display/vga-isa.c | 9 +
>>   1 file changed, 9 insertions(+)
>> diff --git a/hw/display/vga-isa.c b/hw/display/vga-isa.c
>> index 90851e730b..69db502dde 100644
>> --- a/hw/display/vga-isa.c
>> +++ b/hw/display/vga-isa.c
>> @@ -61,6 +61,15 @@ static void vga_isa_realizefn(DeviceState *dev, Error 
>> **errp)
>>   MemoryRegion *vga_io_memory;
>>   const MemoryRegionPortio *vga_ports, *vbe_ports;
>> +/*
>> + * some machines register VGA by default, so instead of aborting
>> + * it, show a message and ignore this device.
>> + */
>> +if (qemu_ram_block_by_name("vga.vram")) {
>> +error_report("vga.vram is already registered, ignoring this 
>> device");
>> +return;
>> +}
>
> I think we should not ignore the error, but rather turn this into a
> proper error (instead of aborting).
>
> So if you replace error_report(...) with error_setg(errp, ...), the
> patch should be fine.

Agreed.

error_report() in a function with an Error **errp parameter is almost
always wrong.

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

[Jose Ricardo Ziviani]

Hello Thomas and Gerd,

Thank you for reviewing it. Sending a v2 soon.

Thank you very much!

On 16/08/2021 02:05, Gerd Hoffmann wrote:

   Hi,


+if (qemu_ram_block_by_name("vga.vram")) {
+error_report("vga.vram is already registered, ignoring this device");
+return;
+}

I think we should not ignore the error, but rather turn this into a proper
error (instead of aborting).

Yes.  Silently fixing up things automatically tends to be worse long-term.

take care,
   Gerd

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

[Gerd Hoffmann]

  Hi,

> > +if (qemu_ram_block_by_name("vga.vram")) {
> > +error_report("vga.vram is already registered, ignoring this 
> > device");
> > +return;
> > +}
> 
> I think we should not ignore the error, but rather turn this into a proper
> error (instead of aborting).

Yes.  Silently fixing up things automatically tends to be worse long-term.

take care,
  Gerd

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

[Thomas Huth]

On 14/08/2021 01.36, 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 such device automaticaly, so it's
not obvious that a VGA device already exists. This patch changes
this behavior by displaying a message and ignoring that device,
starting qemu normally.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/44
Signed-off-by: Jose R. Ziviani 
---
  hw/display/vga-isa.c | 9 +
  1 file changed, 9 insertions(+)

diff --git a/hw/display/vga-isa.c b/hw/display/vga-isa.c
index 90851e730b..69db502dde 100644
--- a/hw/display/vga-isa.c
+++ b/hw/display/vga-isa.c
@@ -61,6 +61,15 @@ static void vga_isa_realizefn(DeviceState *dev, Error **errp)
  MemoryRegion *vga_io_memory;
  const MemoryRegionPortio *vga_ports, *vbe_ports;
  
+/*

+ * some machines register VGA by default, so instead of aborting
+ * it, show a message and ignore this device.
+ */
+if (qemu_ram_block_by_name("vga.vram")) {
+error_report("vga.vram is already registered, ignoring this device");
+return;
+}


I think we should not ignore the error, but rather turn this into a proper 
error (instead of aborting).


So if you replace error_report(...) with error_setg(errp, ...), the patch 
should be fine.


 Thomas

[PATCH] 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 such device automaticaly, so it's
not obvious that a VGA device already exists. This patch changes
this behavior by displaying a message and ignoring that device,
starting qemu normally.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/44
Signed-off-by: Jose R. Ziviani 
---
 hw/display/vga-isa.c | 9 +
 1 file changed, 9 insertions(+)

diff --git a/hw/display/vga-isa.c b/hw/display/vga-isa.c
index 90851e730b..69db502dde 100644
--- a/hw/display/vga-isa.c
+++ b/hw/display/vga-isa.c
@@ -61,6 +61,15 @@ static void vga_isa_realizefn(DeviceState *dev, Error **errp)
 MemoryRegion *vga_io_memory;
 const MemoryRegionPortio *vga_ports, *vbe_ports;
 
+/*
+ * some machines register VGA by default, so instead of aborting
+ * it, show a message and ignore this device.
+ */
+if (qemu_ram_block_by_name("vga.vram")) {
+error_report("vga.vram is already registered, ignoring this device");
+return;
+}
+
 s->global_vmstate = true;
 vga_common_init(s, OBJECT(dev));
 s->legacy_address_space = isa_address_space(isadev);
-- 
2.32.0