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

[Cédric Le Goater]

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.

> 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.

C.