Re: [Qemu-block] [Qemu-devel] [PATCH 05/10] ppc405_boards: Don't size flash memory to match backing image

[Markus Armbruster]

David Gibson <address@hidden> writes:

> On Thu, Feb 21, 2019 at 05:31:30PM +0100, Markus Armbruster wrote:
>> Alex Bennée <address@hidden> writes:
>> 
>> > Markus Armbruster <address@hidden> writes:
>> >
>> >> Machine "ref405ep" maps its flash memory at address 2^32 - image size.
>> >> Image size is rounded up to the next multiple of 64KiB.  Useless,
>> >> because pflash_cfi02_realize() fails with "failed to read the initial
>> >> flash content" unless the rounding is a no-op.
>> >>
>> >> If the image size exceeds 0x80000 Bytes, we overlap first SRAM, then
>> >> other stuff.  No idea how that would play out, but a useful outcomes
>> >> seem unlikely.
>> >>
>> >> Map the flash memory at fixed address 0xFFF80000 with size 512KiB,
>> >> regardless of image size, to match the physical hardware.
>> >>
>> >> Machine "taihu" maps its boot flash memory similarly.  The code even
>> >> has a comment /* XXX: should check that size is 2MB */, followed by
>> >> disabled code to adjust the size to 2MiB regardless of image size.
>> >>
>> >> Its code to map its application flash memory looks the same, except
>> >> there the XXX comment asks for 32MiB, and the code to adjust the size
>> >> isn't disabled.  Note that pflash_cfi02_realize() fails with "failed
>> >> to read the initial flash content" for images smaller than 32MiB.
>> >>
>> >> Map the boot flash memory at fixed address 0xFFE00000 with size 2MiB,
>> >> to match the physical hardware.  Delete dead code from application
>> >> flash mapping, and simplify some.
>> >>
>> >> Cc: David Gibson <address@hidden>
>> >> Signed-off-by: Markus Armbruster <address@hidden>
>> >> ---
>> >>  hw/ppc/ppc405_boards.c | 53 +++++++++++++-----------------------------
>> >>  1 file changed, 16 insertions(+), 37 deletions(-)
>> >>
>> >> diff --git a/hw/ppc/ppc405_boards.c b/hw/ppc/ppc405_boards.c
>> >> index f47b15f10e..728154aebb 100644
>> >> --- a/hw/ppc/ppc405_boards.c
>> >> +++ b/hw/ppc/ppc405_boards.c
>> >> @@ -158,7 +158,7 @@ static void ref405ep_init(MachineState *machine)
>> >>      target_ulong kernel_base, initrd_base;
>> >>      long kernel_size, initrd_size;
>> >>      int linux_boot;
>> >> -    int fl_idx, fl_sectors, len;
>> >> +    int len;
>> >>      DriveInfo *dinfo;
>> >>      MemoryRegion *sysmem = get_system_memory();
>> >>
>> >> @@ -185,26 +185,19 @@ static void ref405ep_init(MachineState *machine)
>> >>  #ifdef DEBUG_BOARD_INIT
>> >>      printf("%s: register BIOS\n", __func__);
>> >>  #endif
>> >> -    fl_idx = 0;
>> >>  #ifdef USE_FLASH_BIOS
>> >> -    dinfo = drive_get(IF_PFLASH, 0, fl_idx);
>> >> +    dinfo = drive_get(IF_PFLASH, 0, 0);
>> >>      if (dinfo) {
>> >> -        BlockBackend *blk = blk_by_legacy_dinfo(dinfo);
>> >> -
>> >> -        bios_size = blk_getlength(blk);
>> >> -        fl_sectors = (bios_size + 65535) >> 16;
>> >>  #ifdef DEBUG_BOARD_INIT
>> >> -        printf("Register parallel flash %d size %lx"
>> >> -               " at addr %lx '%s' %d\n",
>> >> -               fl_idx, bios_size, -bios_size,
>> >> -               blk_name(blk), fl_sectors);
>> >> +        printf("Register parallel flash\n");
>> >>  #endif
>> >> -        pflash_cfi02_register((uint32_t)(-bios_size),
>> >> +        bios_size = 0x80000;
>> >
>> >  bios_size = 8 * MiB?
>> 
>> The next line has base address 0xFFF80000.  I picked 0x80000 to make
>> 0xFFF80000 + 0x80000 == 0 mod 2^32 more obvious.
>> 
>> If I change 0x80000 to 8 * MiB, the size is more obvious, but "at end of
>> 32 bit address space" less so.
>> 
>> If I additionally change the base address back to ((uint32_t)-bios_size,
>> "at end of 32 bit address space" is obvious again, but the actual base
>> address less so.
>
> I have a weak preference for ((uint32_t)-bios_size), with bios_size =
> 8 * MiB.
>
>> 
>> I don't really care myself.  David, you're the maintainer, do you have a
>> preference?
>> 
>> >> +        pflash_cfi02_register(0xFFF80000,
>> >>                                NULL, "ef405ep.bios", bios_size,
>> >> -                              blk, 65536, fl_sectors, 1,
>> >> +                              dinfo ? blk_by_legacy_dinfo(dinfo) : NULL,
>> >> +                              65536, bios_size / 65536, 1,
>> >
>> > 64 * KiB?
>> 
>> David, same question (two additional instances below).
>
> Here I think 64 * KiB would be nice in each of those places.  Again,
> only a weak preference.

Your weak preference is enough to tip my scales.  Thanks!