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

[Markus Armbruster <armbru@redhat.com>]

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?
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?"