Re: [PATCH 2/4] hw/block/fdc: Remove the check_media_rate property

[Laurent Vivier]

Le 08/02/2021 à 08:05, Thomas Huth a écrit :
> On 05/02/2021 21.15, John Snow wrote:
>> On 2/5/21 1:37 AM, Thomas Huth wrote:
>>> On 05/02/2021 01.40, John Snow wrote:
>>>> On 2/3/21 12:18 PM, Thomas Huth wrote:
>>>>> This was only required for the pc-1.0 and earlier machine types.
>>>>> Now that these have been removed, we can also drop the corresponding
>>>>> code from the FDC device.
>>>>>
>>>>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>>>>> ---
>>>>>   hw/block/fdc.c             | 17 ++---------------
>>>>>   tests/qemu-iotests/172.out | 35 -----------------------------------
>>>>>   2 files changed, 2 insertions(+), 50 deletions(-)
>>>>>
>>>>> diff --git a/hw/block/fdc.c b/hw/block/fdc.c
>>>>> index 292ea87805..198940e737 100644
>>>>> --- a/hw/block/fdc.c
>>>>> +++ b/hw/block/fdc.c
>>>>> @@ -874,7 +874,6 @@ struct FDCtrl {
>>>>>           FloppyDriveType type;
>>>>>       } qdev_for_drives[MAX_FD];
>>>>>       int reset_sensei;
>>>>> -    uint32_t check_media_rate;
>>>>
>>>> I am a bit of a dunce when it comes to the compatibility properties... 
>>>> does this mess with the
>>>> migration format?
>>>>
>>>> I guess it doesn't, since it's not in the VMSTATE declaration.
>>>>
>>>> Hmmmm, alright.
>>>
>>> I think that should be fine, yes.
>>>
>>>>>       FloppyDriveType fallback; /* type=auto failure fallback */
>>>>>       /* Timers state */
>>>>>       uint8_t timer0;
>>>>> @@ -1021,18 +1020,10 @@ static const VMStateDescription 
>>>>> vmstate_fdrive_media_changed = {
>>>>>       }
>>>>>   };
>>>>> -static bool fdrive_media_rate_needed(void *opaque)
>>>>> -{
>>>>> -    FDrive *drive = opaque;
>>>>> -
>>>>> -    return drive->fdctrl->check_media_rate;
>>>>> -}
>>>>> -
>>>>>   static const VMStateDescription vmstate_fdrive_media_rate = {
>>>>>       .name = "fdrive/media_rate",
>>>>>       .version_id = 1,
>>>>>       .minimum_version_id = 1,
>>>>> -    .needed = fdrive_media_rate_needed,
>>>>>       .fields = (VMStateField[]) {
>>>>>           VMSTATE_UINT8(media_rate, FDrive),
>>>>>           VMSTATE_END_OF_LIST()
>>>>> @@ -1689,8 +1680,7 @@ static void fdctrl_start_transfer(FDCtrl *fdctrl, 
>>>>> int direction)
>>>>>       /* Check the data rate. If the programmed data rate does not match
>>>>>        * the currently inserted medium, the operation has to fail. */
>>>>> -    if (fdctrl->check_media_rate &&
>>>>> -        (fdctrl->dsr & FD_DSR_DRATEMASK) != cur_drv->media_rate) {
>>>>> +    if ((fdctrl->dsr & FD_DSR_DRATEMASK) != cur_drv->media_rate) {
>>>>>           FLOPPY_DPRINTF("data rate mismatch (fdc=%d, media=%d)\n",
>>>>>                          fdctrl->dsr & FD_DSR_DRATEMASK, 
>>>>> cur_drv->media_rate);
>>>>>           fdctrl_stop_transfer(fdctrl, FD_SR0_ABNTERM, FD_SR1_MA, 0x00);
>>>>> @@ -2489,8 +2479,7 @@ static void fdctrl_result_timer(void *opaque)
>>>>>           cur_drv->sect = (cur_drv->sect % cur_drv->last_sect) + 1;
>>>>>       }
>>>>>       /* READ_ID can't automatically succeed! */
>>>>> -    if (fdctrl->check_media_rate &&
>>>>> -        (fdctrl->dsr & FD_DSR_DRATEMASK) != cur_drv->media_rate) {
>>>>> +    if ((fdctrl->dsr & FD_DSR_DRATEMASK) != cur_drv->media_rate) {
>>>>>           FLOPPY_DPRINTF("read id rate mismatch (fdc=%d, media=%d)\n",
>>>>>                          fdctrl->dsr & FD_DSR_DRATEMASK, 
>>>>> cur_drv->media_rate);
>>>>>           fdctrl_stop_transfer(fdctrl, FD_SR0_ABNTERM, FD_SR1_MA, 0x00);
>>>>> @@ -2895,8 +2884,6 @@ static Property isa_fdc_properties[] = {
>>>>>       DEFINE_PROP_UINT32("dma", FDCtrlISABus, dma, 2),
>>>>>       DEFINE_PROP_DRIVE("driveA", FDCtrlISABus, 
>>>>> state.qdev_for_drives[0].blk),
>>>>>       DEFINE_PROP_DRIVE("driveB", FDCtrlISABus, 
>>>>> state.qdev_for_drives[1].blk),
>>>>> -    DEFINE_PROP_BIT("check_media_rate", FDCtrlISABus, 
>>>>> state.check_media_rate,
>>>>> -                    0, true),
>>>>
>>>> Could you theoretically set this via QOM commands in QMP, and claim that 
>>>> this is a break in
>>>> behavior?
>>>>
>>>> Though, it's ENTIRELY undocumented, so ... it's probably fine, I think. 
>>>> Probably. (Please soothe
>>>> my troubled mind.)
>>>
>>> A user actually could mess with this property even on the command line, 
>>> e.g. by using:
>>>
>>>   qemu-system-x86_64 -global isa-fdc.check_media_rate=false
>>>
>>> ... but, as you said, it's completely undocumented, the property is really 
>>> just there for the
>>> internal use of machine type compatibility. We've done such clean-ups in 
>>> the past already, see
>>> e.g. c6026998eef382d7ad76 or 2a4dbaf1c0db2453ab78f, so I think this should 
>>> be fine. But if you
>>> disagree, I could replace this by a patch that adds this property to the 
>>> list of deprecated
>>> features instead, so we could at least remove it after it has been 
>>> deprecated for two releases?
>>>
>>
>> I don't think it's necessary, personally -- just wanted to make sure I knew 
>> the exact stakes here.
>>
>> Reviewed-by: John Snow <jsnow@redhat.com>
>> Acked-by: John Snow <jsnow@redhat.com>
> 
> Thanks! ... since the first patch has already been merged through Michael's 
> tree, could you then
> please take this patch here through your floppy / block branch, John? Or 
> maybe it could also go via
> qemu-trivial?

Applied to my trivial-patches branch.

Thanks,
Laurent