Re: [Qemu-devel] [RFC PATCH v6 1/4] hw/block: better reporting on pflash backing file mismatch

[Markus Armbruster <armbru@redhat.com>]

Alex Bennée <alex.bennee@linaro.org> writes:

> Markus Armbruster <armbru@redhat.com> writes:
>
>> From: Alex Bennée <alex.bennee@linaro.org>
>>
>> It looks like there was going to be code to check we had some sort of
>> alignment so let's replace it with an actual check.  Reject undersized
>> images with "device needs N bytes, backing file provides only M
>> bytes".  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.  Continue to accept oversized images, but warn
>> "device needs N bytes, rest ignored".
>>
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> ---
>>  hw/block/pflash_cfi01.c | 29 ++++++++++++++++++++++-------
>>  1 file changed, 22 insertions(+), 7 deletions(-)
>>
>> diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
>> index 9d1c356eb6..75ce8ef489 100644
>> --- a/hw/block/pflash_cfi01.c
>> +++ b/hw/block/pflash_cfi01.c
>> @@ -45,6 +45,7 @@
>>  #include "qemu/bitops.h"
>>  #include "qemu/host-utils.h"
>>  #include "qemu/log.h"
>> +#include "qemu/error-report.h"
>>  #include "hw/sysbus.h"
>>  #include "sysemu/sysemu.h"
>>  #include "trace.h"
>> @@ -730,13 +731,6 @@ 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
>> -
>>      memory_region_init_rom_device(
>>          &pfl->mem, OBJECT(dev),
>>          &pflash_cfi01_ops,
>> @@ -763,6 +757,27 @@ static void pflash_cfi01_realize(DeviceState *dev, Error **errp)
>>      }
>>
>>      if (pfl->blk) {
>> +        /*
>> +         * Validate the backing store is the right size for pflash
>> +         * devices. If the user supplies a larger file we ignore the
>> +         * tail.
>> +         */
>> +        int64_t backing_len = blk_getlength(pfl->blk);
>> +        if (backing_len < 0) {
>> +            error_setg(errp, "unable to check size of backing file");
>> +            return;
>> +        }
>> +
>> +        if (backing_len < total_len) {
>> +            error_setg(errp, "device needs %" PRIu64 " bytes, "
>> +                       "backing file provides only %" PRIu64 " bytes",
>> +                       total_len, backing_len);
>> +            return;
>> +        } else if (backing_len > total_len) {
>> +            warn_report("device needs %" PRIu64 " bytes, rest ignored",
>> +                        total_len);
>> +        }
>
> As discussed elsewhere I'm happy for this just to error out with a
> useful error message.

I'll do that in the next spin.  Thanks!

>> +
>>          /* read the initial flash content */
>>          ret = blk_pread(pfl->blk, 0, pfl->storage, total_len);
>
>
> --
> Alex Bennée