Re: [PATCH v2 4/4] vga/cirrus: deprecate, don't build by default

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 3/6/24 13:40, Daniel P. Berrangé wrote:
> On Thu, May 30, 2024 at 01:22:11PM +0100, Mark Cave-Ayland wrote:
>> On 30/05/2024 12:40, BALATON Zoltan wrote:
>>
>>> On Thu, 30 May 2024, Gerd Hoffmann wrote:
>>>> stdvga is the much better option.
>>>>
>>>> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
>>>> ---
>>>> hw/display/cirrus_vga.c     | 1 +
>>>> hw/display/cirrus_vga_isa.c | 1 +
>>>> hw/display/Kconfig          | 1 -
>>>> 3 files changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
>>>> index 150883a97166..81421be1f89d 100644
>>>> --- a/hw/display/cirrus_vga.c
>>>> +++ b/hw/display/cirrus_vga.c
>>>> @@ -3007,6 +3007,7 @@ static void cirrus_vga_class_init(ObjectClass
>>>> *klass, void *data)
>>>>      dc->vmsd = &vmstate_pci_cirrus_vga;
>>>>      device_class_set_props(dc, pci_vga_cirrus_properties);
>>>>      dc->hotpluggable = false;
>>>> +    klass->deprecation_note = "use stdvga instead";
>>>> }
>>>>
>>>> static const TypeInfo cirrus_vga_info = {
>>>> diff --git a/hw/display/cirrus_vga_isa.c b/hw/display/cirrus_vga_isa.c
>>>> index 84be51670ed8..3abbf4dddd90 100644
>>>> --- a/hw/display/cirrus_vga_isa.c
>>>> +++ b/hw/display/cirrus_vga_isa.c
>>>> @@ -85,6 +85,7 @@ static void isa_cirrus_vga_class_init(ObjectClass
>>>> *klass, void *data)
>>>>      dc->realize = isa_cirrus_vga_realizefn;
>>>>      device_class_set_props(dc, isa_cirrus_vga_properties);
>>>>      set_bit(DEVICE_CATEGORY_DISPLAY, dc->categories);
>>>> +    klass->deprecation_note = "use stdvga instead";
>>>
>>> Excepr some old OSes work better with this than stdvga so could this be
>>> left and not removed? Does it cause a lot of work to keep this device? I
>>> thought it's stable already and were not many changes for it lately. If
>>> something works why drop it?
>>
>> Seconded: whilst stdvga is preferred, there are a lot of older OSs that work
>> well in QEMU using the Cirrus emulation. I appreciate that the code could do
>> with a bit of work, but is there a more specific reason that it should be
>> deprecated?
> 
> I think there's different answers here for upstream vs downstream.
> 
> Upstream QEMU's scope is to emulate pretty much arbitrary hardware that
> may have existed at any point in time. Emulating Cirrus is very much
> in scope upstream, and even if there are other better VGA devices, that
> doesn't make emulation of Cirrus redundant.
> 
> Downstream is a different matter - if a downstream vendor wants to be
> opinionated and limit the scope of devices they ship to customers, it
> is totally valid to cull Cirrus.

Few years ago I suggested qemu_security_policy_taint() "which allows
unsafe (read "not very maintained") code to 'taint' QEMU security
policy." (Gerd FYI):
https://lore.kernel.org/qemu-devel/20210908232024.2399215-1-philmd@redhat.com/


Upstream we could add a boolean in DeviceClass about device security
status / maintenance (or enum or bitfield); then downstreams could
use it to be sure unsafe devices aren't linked in.


> IOW, I think device deprecation *framework* is relevant to include
> upstream, but most actual usage of it will be downstream.
> 
> Upstream might use *object* deprecation, if we replace an backend
> implementation with a different one.
> 
> With regards,
> Daniel