[PATCH v3] vga: don't abort when adding a duplicate isa-vga device

[PATCH v3] 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
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
---
v2 to v3: Improved error message
v1 to v2: Use error_setg instead of error_report

 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..30d55b41c3 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, "'isa-vga' device 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 v3] vga: don't abort when adding a duplicate isa-vga device

[Thomas Huth]

On 16/08/2021 15.55, 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
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
> ---
> v2 to v3: Improved error message
> v1 to v2: Use error_setg instead of error_report
> 
>   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..30d55b41c3 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, "'isa-vga' device already registered");
> +        return;
> +    }
> +
>       s->global_vmstate = true;
>       vga_common_init(s, OBJECT(dev));
>       s->legacy_address_space = isa_address_space(isadev);
> 

Reviewed-by: Thomas Huth <thuth@redhat.com>

Re: [PATCH v3] vga: don't abort when adding a duplicate isa-vga device

[Mark Cave-Ayland]

On 17/08/2021 08:25, Thomas Huth wrote:

> On 16/08/2021 15.55, 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
>> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
>> ---
>> v2 to v3: Improved error message
>> v1 to v2: Use error_setg instead of error_report
>>
>>   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..30d55b41c3 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, "'isa-vga' device already registered");
>> +        return;
>> +    }
>> +
>>       s->global_vmstate = true;
>>       vga_common_init(s, OBJECT(dev));
>>       s->legacy_address_space = isa_address_space(isadev);
>>
> 
> Reviewed-by: Thomas Huth <thuth@redhat.com>

Instead of checking for the presence of the vga.vram block, would it be better to use 
the standard object_resolve_path_type() method to check for the presence of the 
existing isa-vga device instead? See 
https://lists.gnu.org/archive/html/qemu-devel/2021-07/msg00717.html for how this was 
done for virgl.


ATB,

Mark.

Re: [PATCH v3] vga: don't abort when adding a duplicate isa-vga device

[Philippe Mathieu-Daudé]

On 8/17/21 9:36 AM, Mark Cave-Ayland wrote:
> On 17/08/2021 08:25, Thomas Huth wrote:
> 
>> On 16/08/2021 15.55, 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
>>> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>> Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
>>> ---
>>> v2 to v3: Improved error message
>>> v1 to v2: Use error_setg instead of error_report
>>>
>>>   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..30d55b41c3 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, "'isa-vga' device already registered");
>>> +        return;
>>> +    }
>>> +
>>>       s->global_vmstate = true;
>>>       vga_common_init(s, OBJECT(dev));
>>>       s->legacy_address_space = isa_address_space(isadev);
>>>
>>
>> Reviewed-by: Thomas Huth <thuth@redhat.com>
> 
> Instead of checking for the presence of the vga.vram block, would it be
> better to use the standard object_resolve_path_type() method to check
> for the presence of the existing isa-vga device instead? See
> https://lists.gnu.org/archive/html/qemu-devel/2021-07/msg00717.html for
> how this was done for virgl.

I remembered there was a nicer way but couldn't find it.
If this patch were for 6.1, it was good enough. Now it
will be merged in 6.2, I prefer Mark's suggestion.
Jose, do you mind a v4?

Re: [PATCH v3] vga: don't abort when adding a duplicate isa-vga device

[Jose R. Ziviani]

[-- Attachment #1: Type: text/plain, Size: 3007 bytes --]

On Tue, Aug 17, 2021 at 10:07:55AM +0200, Philippe Mathieu-Daudé wrote:
> On 8/17/21 9:36 AM, Mark Cave-Ayland wrote:
> > On 17/08/2021 08:25, Thomas Huth wrote:
> > 
> >> On 16/08/2021 15.55, 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
> >>> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> >>> Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
> >>> ---
> >>> v2 to v3: Improved error message
> >>> v1 to v2: Use error_setg instead of error_report
> >>>
> >>>   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..30d55b41c3 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, "'isa-vga' device already registered");
> >>> +        return;
> >>> +    }
> >>> +
> >>>       s->global_vmstate = true;
> >>>       vga_common_init(s, OBJECT(dev));
> >>>       s->legacy_address_space = isa_address_space(isadev);
> >>>
> >>
> >> Reviewed-by: Thomas Huth <thuth@redhat.com>
> > 
> > Instead of checking for the presence of the vga.vram block, would it be
> > better to use the standard object_resolve_path_type() method to check
> > for the presence of the existing isa-vga device instead? See
> > https://lists.gnu.org/archive/html/qemu-devel/2021-07/msg00717.html for
> > how this was done for virgl.
> 
> I remembered there was a nicer way but couldn't find it.
> If this patch were for 6.1, it was good enough. Now it
> will be merged in 6.2, I prefer Mark's suggestion.
> Jose, do you mind a v4?
> 

Hello people! Thanks for reviewing it.

Sure, I'll send a v4. It's not for 6.1 anyway.

Thank you very much

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Re: [PATCH v3] vga: don't abort when adding a duplicate isa-vga device

[Thomas Huth]

On 16/08/2021 15.55, 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
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
> ---
> v2 to v3: Improved error message
> v1 to v2: Use error_setg instead of error_report
> 
>   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..30d55b41c3 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, "'isa-vga' device already registered");
> +        return;
> +    }
> +
>       s->global_vmstate = true;
>       vga_common_init(s, OBJECT(dev));
>       s->legacy_address_space = isa_address_space(isadev);

v4 of this patch had other issues ... Philippe's rework of the vga-mmio code 
also did not fix the crash ... shall we just go with this v3 of the patch 
again to fix the issue?

  Thomas