[PATCH v4] vga: don't abort when adding a duplicate isa-vga device

[PATCH v4] 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>
---
v3 to v4: Used object_resolve_path_type instead of qemu_ram_block_by_name
          and copied the message from virgl, to give the same user exp.
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..8cea84f2be 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 (object_resolve_path_type("", TYPE_ISA_VGA, NULL)) {
+        error_setg(errp, "at most one %s device is permitted", TYPE_ISA_VGA);
+        return;
+    }
+
     s->global_vmstate = true;
     vga_common_init(s, OBJECT(dev));
     s->legacy_address_space = isa_address_space(isadev);
-- 
2.32.0

Re: [PATCH v4] vga: don't abort when adding a duplicate isa-vga device

[Thomas Huth]

On 17/08/2021 21.26, 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>
> ---
> v3 to v4: Used object_resolve_path_type instead of qemu_ram_block_by_name
>            and copied the message from virgl, to give the same user exp.
> 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..8cea84f2be 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 (object_resolve_path_type("", TYPE_ISA_VGA, NULL)) {
> +        error_setg(errp, "at most one %s device is permitted", TYPE_ISA_VGA);
> +        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 v4] vga: don't abort when adding a duplicate isa-vga device

[Philippe Mathieu-Daudé]

On 8/17/21 9:26 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>
> ---
> v3 to v4: Used object_resolve_path_type instead of qemu_ram_block_by_name
>           and copied the message from virgl, to give the same user exp.
> 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(+)

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

Re: [PATCH v4] vga: don't abort when adding a duplicate isa-vga device

[Mark Cave-Ayland]

On 17/08/2021 20:26, 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>
> ---
> v3 to v4: Used object_resolve_path_type instead of qemu_ram_block_by_name
>            and copied the message from virgl, to give the same user exp.
> 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..8cea84f2be 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 (object_resolve_path_type("", TYPE_ISA_VGA, NULL)) {
> +        error_setg(errp, "at most one %s device is permitted", TYPE_ISA_VGA);
> +        return;
> +    }
> +
>       s->global_vmstate = true;
>       vga_common_init(s, OBJECT(dev));
>       s->legacy_address_space = isa_address_space(isadev);

Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>


ATB,

Mark.