Re: [PATCH-for-6.1 2/2] hw/block/pflash_cfi02: Do not create aliases when not necessary

[Richard Henderson <richard.henderson@linaro.org>]

On 3/25/21 6:09 AM, Philippe Mathieu-Daudé wrote:
> When no mapping is requested, it is pointless to create
> alias regions.
> Only create them when multiple mappings are requested to
> simplify the memory layout. The flatview is not changed.
> 
> For example using 'qemu-system-sh4 -M r2d -S -monitor stdio',
> 
> * before:
> 
>    (qemu) info mtree
>    address-space: memory
>      0000000000000000-ffffffffffffffff (prio 0, i/o): system
>        0000000000000000-0000000000ffffff (prio 0, i/o): pflash
>          0000000000000000-0000000000ffffff (prio 0, romd): alias pflash-alias @r2d.flash 0000000000000000-0000000000ffffff
>        0000000004000000-000000000400003f (prio 0, i/o): r2d-fpga
>        000000000c000000-000000000fffffff (prio 0, ram): r2d.sdram
>    (qemu) info mtree -f
>    FlatView #0
>     AS "memory", root: system
>     AS "cpu-memory-0", root: system
>     Root memory region: system
>      0000000000000000-0000000000ffffff (prio 0, romd): r2d.flash
>      0000000004000000-000000000400003f (prio 0, i/o): r2d-fpga
>      000000000c000000-000000000fffffff (prio 0, ram): r2d.sdram
> 
> * after:
> 
>    (qemu) info mtree
>    address-space: memory
>      0000000000000000-ffffffffffffffff (prio 0, i/o): system
>        0000000000000000-0000000000ffffff (prio 0, romd): r2d.flash
>        0000000004000000-000000000400003f (prio 0, i/o): r2d-fpga
>        000000000c000000-000000000fffffff (prio 0, ram): r2d.sdram
>    (qemu) info mtree -f
>    FlatView #0
>     AS "memory", root: system
>     AS "cpu-memory-0", root: system
>     Root memory region: system
>      0000000000000000-0000000000ffffff (prio 0, romd): r2d.flash
>      0000000004000000-000000000400003f (prio 0, i/o): r2d-fpga
>      000000000c000000-000000000fffffff (prio 0, ram): r2d.sdram
> 
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>   hw/block/pflash_cfi02.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)


Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~

> 
> diff --git a/hw/block/pflash_cfi02.c b/hw/block/pflash_cfi02.c
> index 35e30bb812c..02c514fb6e0 100644
> --- a/hw/block/pflash_cfi02.c
> +++ b/hw/block/pflash_cfi02.c
> @@ -917,8 +917,12 @@ static void pflash_cfi02_realize(DeviceState *dev, Error **errp)
>       pfl->sector_erase_map = bitmap_new(pfl->total_sectors);
>   
>       pfl->rom_mode = true;
> -    pflash_setup_mappings(pfl);
> -    sysbus_init_mmio(SYS_BUS_DEVICE(dev), &pfl->mem);
> +    if (pfl->mappings > 1) {
> +        pflash_setup_mappings(pfl);
> +        sysbus_init_mmio(SYS_BUS_DEVICE(dev), &pfl->mem);
> +    } else {
> +        sysbus_init_mmio(SYS_BUS_DEVICE(dev), &pfl->orig_mem);
> +    }
>   
>       timer_init_ns(&pfl->timer, QEMU_CLOCK_VIRTUAL, pflash_timer, pfl);
>       pfl->status = 0;
>