Re: [PATCH v5 10/11] hw/arm: Wire up BMC boot flash for npcm750-evb and quanta-gsj

[Havard Skinnemoen]

On Fri, Jul 17, 2020 at 1:52 PM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> On 7/17/20 9:18 PM, Havard Skinnemoen wrote:
> > On Fri, Jul 17, 2020 at 2:00 AM Philippe Mathieu-Daudé <f4bug@amsat.org> 
> > wrote:
> >>
> >> On 7/17/20 10:27 AM, Philippe Mathieu-Daudé wrote:
> >>> On 7/17/20 10:03 AM, Thomas Huth wrote:
> >>>> On 17/07/2020 09.48, Philippe Mathieu-Daudé wrote:
> >>>>> +Thomas
> >>>>
> >>>>> On 7/16/20 10:56 PM, Havard Skinnemoen wrote:
> >>>>>> On Wed, Jul 15, 2020 at 1:54 PM Havard Skinnemoen
> >>>>>> <hskinnemoen@google.com> wrote:
> >>>>>>>
> >>>>>>> On Wed, Jul 15, 2020 at 3:57 AM Philippe Mathieu-Daudé 
> >>>>>>> <f4bug@amsat.org> wrote:
> >>>>>>>>
> >>>>>>>> On 7/15/20 11:00 AM, Markus Armbruster wrote:
> >>>>>>>>> Now my point.  Why first make up user configuration, then use that 
> >>>>>>>>> to
> >>>>>>>>> create a BlockBackend, when you could just go ahead and create the
> >>>>>>>>> BlockBackend?
> >>>>>>>>
> >>>>>>>> CLI issue mostly.
> >>>>>>>>
> >>>>>>>> We can solve it similarly to the recent "sdcard: Do not allow 
> >>>>>>>> invalid SD
> >>>>>>>> card sizes" patch:
> >>>>>>>>
> >>>>>>>>  if (!dinfo) {
> >>>>>>>>      error_setg(errp, "Missing SPI flash drive");
> >>>>>>>>      error_append_hint(errp, "You can use a dummy drive using:\n");
> >>>>>>>>      error_append_hint(errp, "-drive if=mtd,driver=null-co,"
> >>>>>>>>                              "read-ones=on,size=64M\n);
> >>>>>>>>      return;
> >>>>>>>>  }
> >>>>>>>>
> >>>>>>>> having npcm7xx_connect_flash() taking an Error* argument,
> >>>>>>>> and MachineClass::init() call it with &error_fatal.
> >>>>>>>
> >>>>>>> Erroring out if the user specifies a configuration that can't possibly
> >>>>>>> boot sounds good to me. Better than trying to come up with defaults
> >>>>>>> that are still not going to result in a bootable system.
> >>>>>>>
> >>>>>>> For testing recovery paths, I think it makes sense to explicitly
> >>>>>>> specify a null device as you suggest.
> >>>>>>
> >>>>>> Hmm, one problem. qom-test fails with
> >>>>>>
> >>>>>> qemu-system-aarch64: Missing SPI flash drive
> >>>>>> You can add a dummy drive using:
> >>>>>> -drive if=mtd,driver=null-co,read-zeroes=on,size=32M
> >>>>>> Broken pipe
> >>>>>> /usr/local/google/home/hskinnemoen/qemu/for-upstream/tests/qtest/libqtest.c:166:
> >>>>>> kill_qemu() tried to terminate QEMU process but encountered exit
> >>>>>> status 1 (expected 0)
> >>>>>> ERROR qom-test - too few tests run (expected 68, got 7)
> >>>>>>
> >>>>>> So it looks like we might need a different solution to this, unless we
> >>>>>> want to make generic tests more machine-aware...
> >>>>
> >>>> I didn't follow the other mails in this thread, but what we usually do
> >>>> in such a case: Add a "if (qtest_enabled())" check to the device or the
> >>>> machine to ignore the error if it is running in qtest mode.
> >>>
> >>> Hmm I'm not sure it works in this case. We could do:
> >>>
> >>>   if (!dinfo) {
> >>>      if (qtest) {
> >>>         /* create null drive for qtest */
> >>>         opts = ...;
> >>>         dinfo = drive_new(opts, IF_MTD, &error_abort);
> >>>      } else {
> >>>         /* teach user to use proper CLI */
> >>>         error_setg(errp, "Missing SPI flash drive");
> >>>         error_append_hint(errp, "You can use a dummy drive using:\n");
> >>>         error_append_hint(errp, "-drive if=mtd,driver=null-co,"
> >>>                                 "read-ones=on,size=64M\n);
> >>>      }
> >>>   }
> >>>
> >>> But I'm not sure Markus will enjoy it :)
> >>>
> >>> Markus, any better idea about how to handle that with automatic qtests?
> >>
> >> FWIW IDE device has a concept of "Anonymous BlockBackend for an empty
> >> drive":
> >>
> >> static void ide_dev_initfn(IDEDevice *dev, IDEDriveKind kind, Error **errp)
> >> {
> >>     IDEBus *bus = DO_UPCAST(IDEBus, qbus, dev->qdev.parent_bus);
> >>     IDEState *s = bus->ifs + dev->unit;
> >>     int ret;
> >>
> >>     if (!dev->conf.blk) {
> >>         if (kind != IDE_CD) {
> >>             error_setg(errp, "No drive specified");
> >>             return;
> >>         } else {
> >>             /* Anonymous BlockBackend for an empty drive */
> >>             dev->conf.blk = blk_new(qemu_get_aio_context(), 0,
> >> BLK_PERM_ALL);
> >>             ret = blk_attach_dev(dev->conf.blk, &dev->qdev);
> >>             assert(ret == 0);
> >>         }
> >>     }
> >
> > Could someone please remind me what problem we're trying to solve here?
>
> Sorry, out of the scope of your series, which is fine with the current
> code base :)
>
> > Currently, if the user (or test) doesn't provide a drive, we pass NULL
> > as the block backend to m25p80. This means we'll take the code path in
> > m25p_realize() that does
> >
> >         trace_m25p80_binding_no_bdrv(s);
> >         s->storage = blk_blockalign(NULL, s->size);
> >         memset(s->storage, 0xFF, s->size);
> >
> > which will look like a freshly chip-erased flash chip.
> >
> > Are we looking for a more elegant way to replace those three lines of
> > code (+ a couple of conditionals in the writeback paths)?
>
> Yes, I am. Anyway, unrelated to your work, sorry if it confused you.

OK, great, I'll be happy to contribute to that. I was just a little
worried that my series was getting blocked behind it.

> >
> > But we don't even have a dummy device that looks like an erased flash 
> > chip...
>
> No, this is still the design stage, but your series has a quality that
> let us foreseen a bit where we are heading...
>
> >
> > Havard
> >