Re: [PATCH v2] m25p80: Improve error when the backend file size does not match the device

[Markus Armbruster]

Cédric Le Goater <clg@kaod.org> writes:

> On 11/16/22 07:56, Markus Armbruster wrote:
>> Cédric Le Goater <clg@kaod.org> writes:
>> 
>>> Currently, when a block backend is attached to a m25p80 device and the
>>> associated file size does not match the flash model, QEMU complains
>>> with the error message "failed to read the initial flash content".
>>> This is confusing for the user.
>>>
>>> Use blk_check_size_and_read_all() instead of blk_pread() to improve
>>> the reported error.
>>>
>>> Signed-off-by: Cédric Le Goater <clg@kaod.org>
>>> ---
>>>   hw/block/m25p80.c | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
>>> index 02adc87527..68a757abf3 100644
>>> --- a/hw/block/m25p80.c
>>> +++ b/hw/block/m25p80.c
>>> @@ -24,6 +24,7 @@
>>>  #include "qemu/osdep.h"
>>>  #include "qemu/units.h"
>>>  #include "sysemu/block-backend.h"
>>> +#include "hw/block/block.h"
>>>  #include "hw/qdev-properties.h"
>>>  #include "hw/qdev-properties-system.h"
>>>  #include "hw/ssi/ssi.h"
>>> @@ -1614,8 +1615,7 @@ static void m25p80_realize(SSIPeripheral *ss, Error 
>>> **errp)
>>>          trace_m25p80_binding(s);
>>>          s->storage = blk_blockalign(s->blk, s->size);
>>>  
>>> -        if (blk_pread(s->blk, 0, s->size, s->storage, 0) < 0) {
>>> -            error_setg(errp, "failed to read the initial flash content");
>>> +        if (!blk_check_size_and_read_all(s->blk, s->storage, s->size, 
>>> errp)) {
>>>              return;
>>>          }
>>>      } else {
>> 
>> Ignorant question: what does blk_pread() on short read?  Does it fail?
>
> an underlying call to blk_check_byte_request() makes it fail.

Thanks!

>> Or does it succeed, returning how much it read?  I tried to find an
>> answer in function comments, no luck.
>> 
>> Are there more instances of "we fill some fixed-size memory (such as a
>> ROM or flash) from a block backend?"
>
> Yes. There are other similar devices :  nand, nvram, pnv_pnor, etc.

I think they should all be converted to blk_check_size_and_read_all().
Not a prerequisite for getting this patch merged.  Volunteers?