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

[Alex Bennée]

Markus Armbruster <address@hidden> writes:

> From: Alex Bennée <address@hidden>
>
> 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 <address@hidden>
> Reviewed-by: Laszlo Ersek <address@hidden>
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>  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.

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


--
Alex Bennée