Re: [PATCH v9 2/2] hw/i386: Add the ramfb romfile compatibility

[Zhao Liu <zhao1.liu@intel.com>]

On Thu, Jul 03, 2025 at 11:03:15PM -0400, Shaoqin Huang wrote:
> Date: Thu,  3 Jul 2025 23:03:15 -0400
> From: Shaoqin Huang <shahuang@redhat.com>
> Subject: [PATCH v9 2/2] hw/i386: Add the ramfb romfile compatibility
> 
> ramfb is a sysbus device so it can only used for machine types where it
> is explicitly enabled:
> 
>   # git grep machine_class_allow_dynamic_sysbus_dev.*TYPE_RAMFB_DEVICE
>   hw/arm/virt.c:    machine_class_allow_dynamic_sysbus_dev(mc,
> 		  TYPE_RAMFB_DEVICE);
>   hw/i386/microvm.c:    machine_class_allow_dynamic_sysbus_dev(mc,
> 		  TYPE_RAMFB_DEVICE);
>   hw/i386/pc_piix.c:    machine_class_allow_dynamic_sysbus_dev(m,
> 		  TYPE_RAMFB_DEVICE);
>   hw/i386/pc_q35.c:    machine_class_allow_dynamic_sysbus_dev(m,
> 		  TYPE_RAMFB_DEVICE);
>   hw/loongarch/virt.c:    machine_class_allow_dynamic_sysbus_dev(mc,
> 		  TYPE_RAMFB_DEVICE);
>   hw/riscv/virt.c:    machine_class_allow_dynamic_sysbus_dev(mc,
> 		  TYPE_RAMFB_DEVICE);
> 
> So these six are the only machine types we have to worry about.
> 
> The three x86 machine types (pc, q35, microvm) will actually use the rom
> (when booting with seabios).
> 
> For arm/riscv/loongarch virt we want to disable the rom.
> 
> This patch sets ramfb romfile option to false by default, except for x86
> machines types (pc, q35, microvm) which need the rom file when booting
> with seabios and machine types <= 10.0 (handling the case of arm virt,
> for compat reasons).
> 
> At the same time, set the "use-legacy-x86-rom" property to true on those
> historical versioned machine types in order to avoid the memory layout
> being changed.
> 
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Shaoqin Huang <shahuang@redhat.com>
> ---
>  hw/core/machine.c             |  2 ++
>  hw/display/ramfb-standalone.c |  2 +-
>  hw/i386/microvm.c             |  3 +++
>  hw/i386/pc_piix.c             | 10 ++++++++++
>  hw/i386/pc_q35.c              |  3 +++
>  hw/vfio/pci.c                 |  2 +-
>  6 files changed, 20 insertions(+), 2 deletions(-)

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>