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

["Jose R. Ziviani" <jziviani@suse.de>]

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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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