Re: [Qemu-devel] [PATCH for-1.7] s390x: fix flat rom load on 32 bit systems

[Alexander Graf]

On 21.11.2013, at 13:24, Cornelia Huck <address@hidden> wrote:

> On Thu, 21 Nov 2013 14:08:22 +0200
> "Michael S. Tsirkin" <address@hidden> wrote:
> 
>> pc-bios/s390-zipl.rom is a flat image so it's expected that
>> loading it as elf will fail.
>> It should fall back on loading a flat file, but doesn't
>> on 32 bit systems, instead it fails printing:
>>    qemu: hardware error: could not load bootloader 's390-zipl.rom'
>> 
>> The result is boot failure.
>> 
>> The reason is that a 64 bit unsigned interger which is set
>> to -1 on error is compared to -1UL which on a 32 bit system
>> with gcc is a 32 bit unsigned interger.
>> Since both are unsigned, no sign extension takes place and
>> comparison evaluates to non-equal.
>> 
>> There's no reason to do clever tricks: -1 will cause
>> sign extension to happen correctly automatically.
>> 
>> Signed-off-by: Michael S. Tsirkin <address@hidden>
>> ---
>> hw/s390x/ipl.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
>> index d69adb2..88115e9 100644
>> --- a/hw/s390x/ipl.c
>> +++ b/hw/s390x/ipl.c
>> @@ -80,7 +80,7 @@ static int s390_ipl_init(SysBusDevice *dev)
>> 
>>         bios_size = load_elf(bios_filename, NULL, NULL, &ipl->start_addr, 
>> NULL,
>>                              NULL, 1, ELF_MACHINE, 0);
>> -        if (bios_size == -1UL) {
>> +        if (bios_size == -1) {
>>             bios_size = load_image_targphys(bios_filename, ZIPL_IMAGE_START,
>>                                             4096);
>>             ipl->start_addr = ZIPL_IMAGE_START;
> 
> Makes sense, but doesn't the kernel loader just below suffer from just
> the same problem?

Yes, initrd too.


Alex