Re: [PATCH 2/9] hw/ide/core: set ERR_STAT in unsupported command completion

[John Snow]

On Fri, Apr 28, 2023 at 9:22 AM Niklas Cassel <nks@flawful.org> wrote:
>
> From: Niklas Cassel <niklas.cassel@wdc.com>
>
> Currently, the first time sending an unsupported command
> (e.g. READ LOG DMA EXT) will not have ERR_STAT set in the completion.
> Sending the unsupported command again, will correctly have ERR_STAT set.
>
> When ide_cmd_permitted() returns false, it calls ide_abort_command().
> ide_abort_command() first calls ide_transfer_stop(), which will call
> ide_transfer_halt() and ide_cmd_done(), after that ide_abort_command()
> sets ERR_STAT in status.
>
> ide_cmd_done() for AHCI will call ahci_write_fis_d2h() which writes the
> current status in the FIS, and raises an IRQ. (The status here will not
> have ERR_STAT set!).
>
> Thus, we cannot call ide_transfer_stop() before setting ERR_STAT, as
> ide_transfer_stop() will result in the FIS being written and an IRQ
> being raised.
>
> The reason why it works the second time, is that ERR_STAT will still
> be set from the previous command, so when writing the FIS, the
> completion will correctly have ERR_STAT set.
>
> Set ERR_STAT before writing the FIS (calling cmd_done), so that we will
> raise an error IRQ correctly when receiving an unsupported command.
>
> Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
> ---
>  hw/ide/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index 45d14a25e9..c144d1155d 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -531,9 +531,9 @@ BlockAIOCB *ide_issue_trim(
>
>  void ide_abort_command(IDEState *s)
>  {
> -    ide_transfer_stop(s);
>      s->status = READY_STAT | ERR_STAT;
>      s->error = ABRT_ERR;
> +    ide_transfer_stop(s);
>  }
>
>  static void ide_set_retry(IDEState *s)
> --
> 2.40.0
>

Seems OK at a glance. Does this change the behavior of
ide_transfer_stop at all? I guess we've been using this order of
operations since 2008 at least. I didn't know C then.

ACK