Re: [PATCH v2 6/6] hw/i386/pc_sysfw: Alias rather than copy isa-bios region

[Philippe Mathieu-Daudé]

On 30/4/24 17:06, Bernhard Beschow wrote:
> In the -bios case the "isa-bios" memory region is an alias to the BIOS mapped
> to the top of the 4G memory boundary. Do the same in the -pflash case, but only
> for new machine versions for migration compatibility. This establishes common
> behavior and makes pflash commands work in the "isa-bios" region which some
> real-world legacy bioses rely on.
Can you amend a diff of 'info mtree' here to see how the layout changes?

> Note that in the sev_enabled() case, the "isa-bios" memory region in the -pflash
> case will now also point to encrypted memory, just like it already does in the
> -bios case.
>
> Signed-off-by: Bernhard Beschow <shentey@gmail.com>
> ---
>   include/hw/i386/pc.h | 1 +
>   hw/i386/pc.c         | 1 +
>   hw/i386/pc_piix.c    | 3 +++
>   hw/i386/pc_q35.c     | 2 ++
>   hw/i386/pc_sysfw.c   | 8 +++++++-
>   5 files changed, 14 insertions(+), 1 deletion(-)
I'm still not convinced we need a migration back compat for this...

> diff --git a/hw/i386/pc_sysfw.c b/hw/i386/pc_sysfw.c
> index 82d37cb376..ac88ad4eb9 100644
> --- a/hw/i386/pc_sysfw.c
> +++ b/hw/i386/pc_sysfw.c
> @@ -135,6 +135,7 @@ static void pc_system_flash_map(PCMachineState *pcms,
>                                   MemoryRegion *rom_memory)
>   {
>       X86MachineState *x86ms = X86_MACHINE(pcms);
> +    PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
>       hwaddr total_size = 0;
>       int i;
>       BlockBackend *blk;
> @@ -184,7 +185,12 @@ static void pc_system_flash_map(PCMachineState *pcms,
>   
>           if (i == 0) {
>               flash_mem = pflash_cfi01_get_memory(system_flash);
> -            pc_isa_bios_init(&x86ms->isa_bios, rom_memory, flash_mem);
> +            if (pcmc->isa_bios_alias) {
> +                x86_isa_bios_init(&x86ms->isa_bios, rom_memory, flash_mem,
> +                                  true);
> +            } else {
> +                pc_isa_bios_init(&x86ms->isa_bios, rom_memory, flash_mem);
> +            }
>   
>               /* Encrypt the pflash boot ROM */
>               if (sev_enabled()) {