Re: [PATCH] hw/block/fdc: account for read and write requests

[Kevin Wolf <kwolf@redhat.com>]

Am 24.08.2026 um 13:41 hat Christian Quante geschrieben:
> hw/block/fdc.c never calls block_acct_*, so a floppy drive stays at
> zero in query-blockstats and "info blockstats" while IDE, ATAPI, SCSI,
> virtio-blk, NVMe and xen-block all report their traffic. That is the
> only interface through which QEMU reports drive activity, so a
> front-end that shows per-drive activity LEDs -- the way 86Box does --
> can light up every bus except the floppy.
> 
> The accounting is already set up for the drive: floppy_drive_realize()
> reaches block_acct_setup() through blkconf_apply_backend_options(), and
> -device floppy carries account-invalid, account-failed and
> stats-intervals through DEFINE_BLOCK_PROPERTIES. The properties can be
> set today, they just have nothing to act on.
> 
> Wrap the five blk_pread()/blk_pwrite() calls in two helpers that
> account for the transfer. The cookie lives on the stack: floppy I/O is
> synchronous throughout, so it never outlives the call and there is no
> device state to migrate, unlike IDE where the cookie sits in the device
> because the transfer is asynchronous -- scsi-disk, nvme, ahci and
> xen-block all keep it in their request state for the same reason.
> 
> Measured with a boot sector that reads 18 sectors from A: and 16 from
> C: and writes two back to each. The disk backend reports rd_ops=16
> rd_bytes=8192 wr_ops=2 wr_bytes=1024 either way, so the guest did the
> same work in both runs; the floppy went from rd_ops=0 wr_ops=0 to
> rd_ops=19 rd_bytes=9728 wr_ops=2 wr_bytes=1024 -- 19 reads being the
> boot sector the BIOS pulls in plus the 18 the guest asks for.
> 
> Signed-off-by: Christian Quante <christian@quante.one>

Thanks, applied to the block branch.

Would you mind adding some assertions that we counted correctly to
some existing I/O in fdc-test as a followup?

Kevin