Re: [RFC PATCH v2 3/3] hw/pflash_cfi01: Allow devices to have a smaller backing device

[Philippe Mathieu-Daudé]

Hi David,

On 2/22/21 10:07 AM, David Edmondson wrote:
> Allow the backing device to be smaller than the extent of the flash
> device by mapping it as a subregion of the flash device region.
> 
> Return zeroes for all reads of the flash device beyond the extent of
> the backing device.
> 
> For writes beyond the extent of the underlying device, fail on
> read-only devices and discard them for writable devices.

This looks much simpler now.

> Signed-off-by: David Edmondson <david.edmondson@oracle.com>
> ---
>  hw/block/pflash_cfi01.c | 108 ++++++++++++++++++++++++++++++----------
>  hw/block/trace-events   |   3 ++
>  2 files changed, 86 insertions(+), 25 deletions(-)

>      if (pfl->blk) {
>          uint64_t perm;
> +
>          pfl->ro = !blk_supports_write_perm(pfl->blk);
>          perm = BLK_PERM_CONSISTENT_READ | (pfl->ro ? 0 : BLK_PERM_WRITE);
>          ret = blk_set_perm(pfl->blk, perm, BLK_PERM_ALL, errp);
>          if (ret < 0) {
>              return;
>          }
> +
> +        inner_len = blk_getlength(pfl->blk);
> +
> +        if (inner_len > outer_len) {
> +            error_setg(errp,
> +                       "block backend provides %" HWADDR_PRIu " bytes, "
> +                       "device limited to %" PRIu64 " bytes",
> +                       inner_len, outer_len);
> +            return;
> +        }

Do you mind extracting this change in a previous patch?

Thanks,

Phil.