Re: [PATCH v2] ata: libata-scsi: abort multi-sector pass-through commands when multi_count is 0

[Niklas Cassel <cassel@kernel.org>]

On Mon, Sep 21, 2026 at 03:25:55AM +0000, Hui Peng wrote:
> When an ATA_12, ATA_16, or ATA_32 pass-through command with a
> multi-sector PIO command opcode (ATA_CMD_READ_MULTI,
> ATA_CMD_WRITE_MULTI, ATA_CMD_READ_MULTI_EXT, ATA_CMD_WRITE_MULTI_EXT, or
> ATA_CMD_WRITE_MULTI_FUA_EXT) is submitted via SG_IO on a device where
> multiple-sector mode is not configured (dev->multi_count == 0),
> ata_scsi_pass_thru() currently logs a warning and still dispatches the
> taskfile. When the DRQ interrupt fires, ata_pio_sectors() triggers
> WARN_ON_ONCE(qc->dev->multi_count == 0) and computes
> nsect = min((qc->nbytes - qc->curbytes) / qc->sect_size, 0) = 0, failing
> to transfer any sectors:
> 
>   ata1.00: invalid multi_count 1 ignored
>   WARNING: drivers/ata/libata-sff.c:666 at ata_pio_sectors+0x27d/0x300
>   Call Trace:
>    <IRQ>
>    ata_sff_hsm_move+0x211/0x22e0
>    __ata_sff_port_intr+0x1c8/0x520
>    ata_bmdma_port_intr+0xa1/0x5b0
>    ata_bmdma_interrupt+0x1f5/0x550
> 
> Per ACS-3 section 7.12.7.21, if IDENTIFY DEVICE word 59 bit 8 is cleared
> to zero (multi_count == 0) and a READ MULTIPLE or WRITE MULTIPLE command
> is received without a preceding successful SET MULTIPLE MODE command, the
> device returns command aborted (ABRT). Per the SAT specification, an ABRT
> error translates to the ABORTED COMMAND sense key with NO ADDITIONAL SENSE
> INFORMATION (0x00, 0x00).
> 
> Fail multi-sector taskfile commands in ata_scsi_pass_thru() with
> ata_scsi_set_sense(dev, scmd, ABORTED_COMMAND, 0, 0) when
> dev->multi_count == 0.
> 
> Tested in QEMU against Linux 7.3.0-rc3 (-device ide-cf, where
> dev->multi_count is 0) by issuing ATA_CMD_SET_MULTI (nsect=1) followed
> by an SG_IO ATA_16 ATA_CMD_READ_MULTI command: on the unfixed kernel
> this triggers WARNING: drivers/ata/libata-sff.c:666 in
> ata_pio_sectors(), whereas on the fixed kernel it immediately completes
> with sense key ABORTED_COMMAND (0x0b, 0x00, 0x00) and 0 warnings.

Testing information is usually placed after "---" so that it does not
get included in the commit message when applied using git am.

I can drop this when applying, no need to send a v3.


Kind regards,
Niklas