Re: [Qemu-devel] [PATCH] hw/block: report when pflash backing file isn't aligned

[Alex Bennée]

Laszlo Ersek <address@hidden> writes:

> On 02/14/19 16:57, Alex Bennée wrote:
>> It looks like there was going to be code to check we had some sort of
>> alignment so lets replace it with an actual check. This is a bit more
>> useful than the enigmatic "failed to read the initial flash content"
>> when we attempt to read the number of bytes the device should have.
>>
>> This is a potential confusing stumbling block when you move from using
>> -bios to using -drive if=pflash,file=blob,format=raw,readonly for
>> loading your firmware code.
>>
>> Signed-off-by: Alex Bennée <address@hidden>
>> ---
>>  hw/block/pflash_cfi01.c | 19 +++++++++++++------
>>  1 file changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
>> index bffb4c40e7..f3251b236c 100644
>> --- a/hw/block/pflash_cfi01.c
>> +++ b/hw/block/pflash_cfi01.c
>> @@ -722,12 +722,19 @@ static void pflash_cfi01_realize(DeviceState *dev, 
>> Error **errp)
>>      }
>>      device_len = sector_len_per_device * blocks_per_device;
>>
>> -    /* XXX: to be fixed */
>> -#if 0
>> -    if (total_len != (8 * 1024 * 1024) && total_len != (16 * 1024 * 1024) &&
>> -        total_len != (32 * 1024 * 1024) && total_len != (64 * 1024 * 1024))
>> -        return NULL;
>> -#endif
>> +    /*
>> +     * Validate the backing store is the right size for pflash
>> +     * devices. It has to be padded to a multiple of the flash block
>> +     * size.
>> +     */
>> +    if (pfl->blk) {
>> +        uint64_t backing_len = blk_getlength(pfl->blk);
>> +        if (device_len != backing_len) {
>> +            error_setg(errp, "backing file wrong size "
>> +                       "(%" PRId64 " != %" PRId64")", backing_len, 
>> device_len);
>> +            return;
>> +        }
>> +    }
>>
>>      memory_region_init_rom_device(
>>          &pfl->mem, OBJECT(dev),
>>
>
> I have two suggestions:
> - backing_len and device_len are both uint64_t; we should print them
>   with PRIu64

blk_getlength actually returns int64_t for some reason (do signed
lengths even make sense? maybe it's for error handling?). But sure I can
make it PRIu64

> - from a user POV, I find it more useful if the error message also shows
>   which quantity is which, not just two inequal numbers.

How about:

  "backing file size (%) not enough for whole device (%)"

?

>
> I don't feel too strongly about this, so up to you.
>
> Thanks,
> Laszlo


--
Alex Bennée